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The result of the proposal was move. 199.125.109.99 ( talk) 17:14, 1 May 2008 (UTC)
Wolfkeeper, you are wrong. See my reply to Steve above. When nothing is physically rotating there can be no centrifugal force. I think that your belief to the contrary lies at the root of this problem. You are backed up by superior numbers, but I believe that you are wrong.
Yesterday, I drew your attention to the fact that the ω of the rotating frame of reference has to also be physically connected to the tangential speed of the particle. If the particle is sitting still in an inertial frame, then there is nothing doing. The situation is quite different from the situation which occurs in a centrifuge.
This analogy extends to Coriolis force. If a bird flies over a rotating children's roundabout, then the Coriolis force is entirely fictitious. There is no physical connection between the two situations.
But in cyclones in the atmosphere, the moving elements of air are physically connected to the larger entrained body of atmosphere. Hence the effects can be real, as like in the centrifuge. I have been trying to impress this point on Rracecarr but without any success. David Tombe ( talk) 07:52, 29 April 2008 (UTC)
Yes, Wolkeeper, inertia is real. But that is not the argument. The argument is about distinguishing between cases in which the effects are purely fictitious and cases in which the effects are real. David Tombe ( talk) 08:29, 29 April 2008 (UTC)
Wolfkeeper, you still don't understand the difference between the real effect which occurs during actual curved path motion, and the fictitious effect which is observed when a stationary particle is observed from a rotating frame of reference. David Tombe ( talk) 12:18, 29 April 2008 (UTC)
Merge the two articles. There is no good reason to split in two articles; they are about the same effect in different situations. ( TimothyRias ( talk) 11:41, 29 April 2008 (UTC))
Wolfkeeper,That was a complete misrepresentation of everything I have been saying. I am the one that has been saying that the effect in the atmosphere is real. The others, such as Rracecarr are the ones that have been saying that it is purely fictitious. You have been sitting on the fence saying that it is not quite fictitious. David Tombe ( talk) 20:07, 29 April 2008 (UTC)
FyzixFighter, There is nothing in any of my edits which you have deleted that either criticizes the orthodox position on rotating coordinate frames or make the claim that centrifugal force is real.
You have been deleting edits which describe in simple terms exactly what centrifugal force is. It is an outward radial acceleration which occurs when an object moves in a curved path. David Tombe ( talk) 20:15, 29 April 2008 (UTC)
No FyzixFighter, I won't give you a source for that fundamental fact. Children learned it in the garden when they swung a bucket of water over their heads. You have simply shown yourself up here as nothing but a trouble maker. You have stormed in on a wikistalking mission and then decided to go and make accusations against me when I hit back. You are just a trouble maker. You are not here to improve the article at all. David Tombe ( talk) 20:46, 29 April 2008 (UTC)
Wolfkeeper, you should merge the articles. Reactive centrifugal force is a knock on effect which occurs when something that is experiencing centrifugal force knocks against something else. It is not even covered in this article because you have turned cause and effect upside down. and it doesn't really need to be covered at all unless you might wish to write a section on it.
There is only one centrifugal force but there is an argument about whether it is real or fictitious. David Tombe ( talk) 12:35, 29 April 2008 (UTC)
David is correct, there is no fictious centrifugal force and your attempt to invent one to satisfy your confused notions of physics is just a fiction itself. 72.64.49.249 ( talk) 13:20, 29 April 2008 (UTC)
When a bucket of water is swung in circular motion, it induces a hydrostatic pressure in the water. That is an effect which is observed from all reference frames. It is absolute. It is quite wrong to state that centrifugal force is an effect which is only observed in rotating frames of reference.
The closest that you could get to making that statement true would be to say that this effect is called 'centrifugal force' when it is observed from a rotating frame of reference but when it is observed from an inertial frame, the modern tendency is to refer to this effect as having been caused by inertia.
This effect, whether we call it centrifugal force or inertia, is not the same as the situation which we are dealing with when we observe a stationary object from a rotating frame. In the latter case, there is no real effect. These two circular motion situations are every bit as different from each other as two important circular motions in electromagnetism that are connected with the Faraday paradox. When we move a charged particle tangentially in the equatorial plane of a magnetic field, we get an induced electromotive force. But when we rotate the magnet on its magnetic axis with the particle stationary, we only get the artificial circle as observed from the frame of the rotating magnet. Nobody has ever said that these two effects are the same. Likewise in mechanics. There are two different effects and only one of these effects is centrifugal force.
Hence, there should be one single article on centrifugal force. Reactive centrifugal force does not need to be mentioned as it is merely a knock on effect in collisions and contact pressure situations. It can however be mentioned in a section, if somebody so wishes it to be. But I hope they manage to get the action and reaction the right way around.
Now moving on to the maths. If you look at the derivation of the rotating frame equations, you will see that ω which refers to the angular velocity of the rotating frame also refers to the angular velocity of the particle. It is a simple vector triangle. The particle velocity is split into two components. In the limit, this becomes a tangential component connected with ω, and a radial component which comes into play for Coriolis purposes.
Hence, these equations only apply to co-rotation, and to real Coriolis force when the radial velocity is physically referenced to the rotating frame such as in the hydrodynamics of the atmosphere, which of course is why the cyclones are real and not merely apparent.
So how should we proceed with a wording which does not conflict with the textbooks?
Centrifugal force is a term used within a rotating frame of reference, and it applies to the outward radial force which acts on objects which are stationary within the rotating frame. This effect can be extended to all curved path motion.
In the inertial frame of reference, this effect is said to be caused by inertia. David Tombe ( talk) 09:23, 30 April 2008 (UTC)
Steve, you mention about a spin off article for reactive centrifugal force. Do you mean another page? Can it not be handled as a section near the end of a united centrifugal force article?
The so-called reactive centrifugal force seems to have caused the editors to overlook a more fundamental division of effects within what modern textbooks call centrifugal force. This division splits along similar lines as in the Faraday paradox.
There is a real effect which occurs in a centrifuge. That is a radial outward pressure associated with actual curved path motion.
There is a fictitious effect which is associated with a stationary object being viewed from a rotating frame.
Personally, I would only use the term centrifugal force to cover for the real effect. But if the textbooks blend the two together under one set of umbrella maths, then we need to specify these two scenarios as per the Bucket argument. We cannot overlook the physical difference on the ostensible grounds of a unifying maths. That would be like overlooking the difference between the time dependent aspect of the Lorentz force and the motion dependent aspect on the grounds that one single equation covers them all.
We must specify the hydrostatic pressure in the rotating bucket as one scenario, and the stars rotating across the sky as another scenario.
We can have an introduction which sticks to textbook terminologies. But we cannot make the blanket assertion that centrifugal force is fictitious. It is sometimes fictitious and sometimes real.
Editors here have devolved all the real stuff to 'reactive centrifugal force' and deemed the rest to be fictitious. That is not a correct division. There is real centrifugal force before any reactions occur at centrifuge walls. David Tombe ( talk) 18:16, 30 April 2008 (UTC)
Wolfkeeper, If you had read the new introduction, you would have seen that it unequivocally maintained the position that the centrifugal force applies to all objects. I disagree with that, but that is the official position.
You reverted me on the false grounds that I had alleged otherwise.
I haven't got a citation that would explicitly state that the coordinate transformation equations only apply to co-rotation. I can see it just by looking at the vector triangle in the derivation. The particle velocity is split into two components. The tangential velocity of the rotating frame becomes one of those components. Hence the two things are physically linked.
The introduction which I have put in now was carefully thought out to cover all aspects of the controversy.
Read it and think about it before you revert it. David Tombe ( talk) 06:19, 1 May 2008 (UTC)
"To the extent to which the object or fluid element co-rotates with the frame, a radial acceleration or a hydrostatic pressure is induced."
A radial acceleration is always induced everywhere in the rotating frame proportional to distance from the axis. It may or may not be balanced or enhanced by other (pseudo)forces, but it's not a matter of the extent of corotation.- ( User) WolfKeeper ( Talk) 06:21, 1 May 2008 (UTC)
Let's examine the existing introduction. This paragraph here,
In some cases, it is convenient to use a rotating reference frame, rather than an inertial reference frame. When this is desirable, coordinate transformations from the inertial reference frame can be applied.
However, to do this correctly, in the rotating reference frame, a centrifugal force must be applied in conjunction with a Coriolis force for the correct equation of motion to be calculated. The centrifugal force depends only on the position and mass of the object it applies to (and does not depend on its velocity), whereas the Coriolis force depends on the velocity and mass of the object but is independent of its position.
is just clutter.
And it says nothing about any of the real effects that would occur in a centrifuge. Neither does it clarify about not to get confused with centripetal force.
Yet you have nevetheless chosen to revert. Your decision was not based on physics arguments. David Tombe ( talk) 06:32, 1 May 2008 (UTC)
Wolfkeeper, when we rotate a bucket of water, centrifugal force creates a hydrostatic pressure in the water. That is a reality and it only happens in the co-rotation scenario.
At the moment, you are in a state of denial for which there seems to be no cure.
You are living in a fictitious world in which you want to pretend that a rotating bucket of water is exactly the same thing as a stationary bucket of water as when viewed from a rotating frame of reference.
They are not the same thing. It is a centrifugal force version of the Faraday paradox.
I tried to compromise with you and retain the initial line that centrifugal force applies to all the objects.
But you seem to be offended at any suggestion at all that centrifugal force can have any element of reality about it.
You are in denial and you are trying to impose your 'fictitiousist' view of the world on everybody else.
I deliberately worded the article to compromise between the mathematical definition and the layman's understanding. You have reverted it to a version which is clearly ill though out, ommitts important facts, and contains alot of unnecessary clutter.
With my introduction, we won't even need a separate article for reactive centrifugal force. The division is a total mess. David Tombe ( talk) 07:17, 1 May 2008 (UTC)
Wolfkeeper, You are in a state of denial. Hydrostatic pressure exists in a rotating bucket of water. That is not original research and it does not require a citation. If you check the wikipedia rules, you will see that no citations are needed for facts that are obvious.
You adhere to some strange view of the world in which everything is relative and that absolute facts such as hydrostatic pressure in a rotating bucket of water do not exist. You do not live in the real world.
I doubt if you ever thought of the Bucket argument before. And now that you have been made aware of it, you have calmly stated that you are going to ignore it.
You are not in a position to be editing articles on real physics. You have made an absolute shambles of these pages and for some reason, everybody seems to be too scared to stand up to you. David Tombe ( talk) 09:09, 1 May 2008 (UTC)
I've just sent a note to David regarding Wikipedia's Neutral Point of View policy and attribution, verifiability and reliable sources principles. I look forward to him providing suitable cites to support his contributions from now on. -- The Anome ( talk) 11:15, 1 May 2008 (UTC)
Reading this only reinforces the perception that Wikipedia is not a valid source for physics information. The perception of Wikipedia is that it is a source of misinformation, and not a source of correct information. The evident fact is that the editors are unwilling to work out a correct version which incorporates the valid criticism of their attempted edits. Mr Wolfkeeper evidently knows nothing, and denies an experimental fact known for thousands of years to be true. Management has now confirmed that course of action, and validated the view that Wikipedia is more about enforcing certain opinions than benefiting from the criticism of independent scholars and experts. Most physics experts I know consider this web site a joke. Wikipedia is a known bad source of information, due to its policy of copying from others without regard to the quality of the information being blindly repeated. I personally have found so many mistakes here that I dont even attempt to correct them. It is not worth the trouble, considering the editor's attitudes. Sorry, but I do not beleive anything you state regarding physics, since your editiors have shown they dont understand what they are doing. Wikipedia dosen't work, and its failure to take into consideration valid criticism only reinforces the bad information already found here. 72.84.69.81 ( talk) 17:20, 1 May 2008 (UTC)
This edit war will only be resolved when there is an open realization of what the war is about. What is the undercurrent that is driving it? And after making yesterday's edits and watching the response, I can now tell you all exactly what it is about.
I inserted a clause in the introduction which drew attention to the fact that in co-rotation situations, we obtain an actual outward acceleration or an actual hydrostatic pressure. Somebody correctly altered that to 'pressure gradient'. That is what constructive collaborative editing is all about. Somebody else changed 'heavier' to 'more dense'. Very good. That's the right idea. Keep improving the matter and making it progressively more and more accurate.
Now unusually, for the first time, my edits were not completely erased. These key bits of information, rather than being completely erased, were moved to a section further down the page where scan readers are less likley to go.
Compare this to the excessive invasion of the first line with copious references to the term 'fictitious'.
Clearly we have a party here who are very keen to emphasize the word 'fictititious', and to hide any examples that might undermine the suitability of the term 'fictitious'.
As regards the original research which I keep getting accused of, I'm still waiting to have that pointed out.
Now at the moment, the introduction is still most unsatisfactory. But I'm going to leave the first line alone and try and tidy up the incoherent clutter below it.
A member of the public reading about centrifugal force wants to see examples. They don't want to read about transformation equations that might be used by scientists behind the scenes.
And we have no examples in the introduction. All we have is a very amateurish statement to the extent that the matter is confusing. That's the kind of thing that somebody who doesn't understand the issue would write.
I'm going to make a different edit later today. When it gets erased, as it almost certainly will be, then we can discuss why. And I guarantee that it will all come down to the fact that the ruling party do not like attention being brought to the fact that centrifugal force can have real effects. It is being sold in the first line as a 'fictitious' effect and that's the party line which it seems must be upheld at any cost. David Tombe ( talk) 08:29, 2 May 2008 (UTC)
Anome, the terminology has never been the main issue, although it's true that I do not like the term 'fictitious force', and I would indeed prefer the term 'inertial force'.
The main issue has been that any attempt to illustrate any semblance of reality surrounding centrifugal force is swiftly removed from the introduction.
Interestingly, one critic yesterday stated that he agreed with my insertions but then ciricized me for having removed other stuff.
So today, I will reinsert a single sentence and not delete the other stuff. I guarantee it will be swiftly deleted.
Then we can discuss why. David Tombe ( talk) 10:07, 2 May 2008 (UTC)
Anome, the lines which PeR removed related to an effect which is absolute and which doesn't depend on which frame of reference we view it from. That outward acceleration or the associated hydrostatic pressure can be viewed from all reference frames. It is not a fictitious effect. That's why PeR removed it. He doesn't want attention brought to absolute effects in conjunction with centrifugal force. David Tombe ( talk) 11:07, 2 May 2008 (UTC)
Plvekamp, it was actually you who reverted me this time. Did you have a reason to do so? PeR has now informed me that his reason was that I hadn't provided sources. But we don't need sources for facts that are not in dispute.
Are you disputing the facts that you erased? David Tombe ( talk) 13:22, 2 May 2008 (UTC)
We are now getting closer to the truth. Of course centrifugal force and centripetal force act as an action-reaction pair in every circular motion situation.
A web link to Donald E. Simanek saying the opposite is not acceptable.
Anybody who claims that centripetal force and centrifugal force do not form an action-reaction pair in circular motion needs to provide a citation from a peer reviewed journal or a reliable textbook. David Tombe ( talk) 14:00, 2 May 2008 (UTC)
FyzixFighter, The statement that you erased read,
When the wall of the centrifuge applies an inward acting centripetal force such as to prevent further radial acceleration, we will have an action-reaction pair.
The wall acts inwards on the object and the object acts outwards on the wall. That is an action-reaction pair. If you insist otherwsie then you are lying and trying to pull the wool over the eyes of the readers.
Reading your passage above, it is clear that your example doesn't apply to the situation in question, and that you have ended up contradicting yourself. Basically, you haven't got a clue what you are talking about. Your reversion was vandalism. David Tombe ( talk) 16:01, 2 May 2008 (UTC)
FyzixFighter, would you then be willing to reinstate the clause, reworded to your own satisfaction? David Tombe ( talk) 17:06, 2 May 2008 (UTC)
FyzixFighter, I thought that the whole introduction was about things as viewed from the rotating frame. And all I did was give an example of a situation where the radial acceleration was real. And you erased it.
Would you consider reinstating that sentence? David Tombe ( talk) 18:35, 2 May 2008 (UTC)
Plvecamp, Does a co-rotating object accelerate outwards or not? David Tombe ( talk) 17:11, 2 May 2008 (UTC)
If it is free (object in car, particle at top of test tube not encountering resistance):
- From inertial frame: No acceleration, no force, moves in straight line (and approaches end while doing so) - From rotating frame: Acceleration outward in accordance with centrifugal pseudoforce covered in this article
When it encounters restraint (door of car, particle encountering resistance or at end of test tube)
- From inertial frame: Centripetal force exerted by restraint on object, object accelerates radially inward - From rotating frame: No acceleration, object is stationary if frame rotates at same speed as constraint
Plvekamp ( talk) 17:28, 2 May 2008 (UTC)
This is so outrageous - "I don't need to specify a frame of reference" - that I'm at a loss for words. That has to be the most naive statement you've uttered yet. If you actually believe that, then nearly all of mathematical physics is beyond your understanding.
Plvekamp (
talk) 18:02, 2 May 2008 (UTC)
A link to Simanek's site is quite acceptable. He is a physics professor, after all. Mangoe ( talk) 16:55, 2 May 2008 (UTC)
Who is this guy??? Please explain which link is the link you are talking about. When you write something you need to be clear about what you mean. —Preceding unsigned comment added by 72.84.70.6 ( talk) 20:55, 3 May 2008 (UTC)
Steve, we'll continue this in a new section. You left off at,
Steve, I'm quite familiar with orbital theory concerning hyperbolas, parabolas, and ellipses. I've had to solve many a difficult problem in this field.
Let me begin with a very simple example. Consider an object high above the Earth that has got zero tangential speed. The only force acting will be gravity, radially downwards. The object will accelerate downwards and the acceleration due to gravity will be equal to r double dot.
Now consider a circular orbit. There will be an additional outward centrifugal force given by mv^2/r. In this case, r double dot will be equal to zero. There will be no net radial force or acceleration.
In elliptical orbits there is a constant oscillation between whether the centrifugal force is greater or the gravity force is greater.
If we consider an ellipse in polar coordinates, centered on the focus, and solve it, we end up with exactly two radial accelerations. There will be an inverse square law acceleration inwards, and a v^2/r acceleration outwards. Centrifugal force is a very real thing.
Now lets get to the point. Your problem with all this is that it contradicts the pet theory that is being pushed on these pages by the 'Fictitious Party'.
That theory is that when an object is at rest in the inertial frame, it will be seen to trace out a circular motion when viewed from a rotating frame. Your argument is that there is a net inward fictitious centripetal force which is the sum of an outward centrifugal force and an inward Coriolis force which is twice as strong.
You will agree that this is the pet theory that the 'Fictitious Party' are trying to promote on these pages. Indeed there was once an entire section devoted to this idea on these pages. It was considered to be much more important than examples of the real effects which your colleagues are currently at this very moment in time trying to hide.
Your theory is wrong to the backbone on a number of counts.
(1) The transformation equations for rotating frames, only apply to co-rotation. This is clear when we look at the derivation. The angular velocity term ω which is ostensibly the angular velocity of the rotating frame, is in fact tied in with the tangential velocity of the particle in question. This is clear by virtue of the fact that it is one of two components of the particle velocity.
(2)In the limit, the v term then becomes the radial velocity. Hence there is no Coriolis force in the radial direction. The Coriolis force and the centrifugal force can never act in the same direction because they are two mutually perpendicular aspects of the same thing. Hence the idea that the Coriolis force could be producing an inward radial force is absolute nonsense.
(3)Even if we ignore points (1) and (2), the final result comes out to be a net inward radial acceleration. That is not circular motion. Circular motion requires a net zero radial acceleration.
So the pet theory of the 'Fictitious Party' is wrong.
When an object is stationary, nothing happens. There is no centrifugal force. There is no hydrostatic pressure gradient induced in a bucket of water.
Those things only happen when the object co-rotates.
And at the moment, your colleagues are desperately trying to hide any references to situations involving co-rotation that result in real physical effects.
There is a group of them who are winning on numbers but who clearly haven't got the first clue about physics but seem to presume that they have.
I would have thought that you would have been intelligent enough to see right through all this, unless perhaps you have got some vested interest in playing along.
But it is all one big fraud. David Tombe ( talk) 17:37, 2 May 2008 (UTC)
Please see above where David told me "I don't need to specify a frame of reference" when I asked him which frame he was referring to. Make your own conclusions. Plvekamp ( talk) 18:43, 2 May 2008 (UTC)
FyzixFighter, in your number (3), why did you drop the radial velocity component r dot r hat?
By the way, I can also recommend prolonged contemplation of this animation. -- The Anome ( talk) 18:55, 2 May 2008 (UTC)
Yes, I saw that. We must have cross wired. See my full reply above. David Tombe ( talk) 19:07, 2 May 2008 (UTC)
FyzixFighter, before your equation (4) can have any meaning, we have to account for all the terms. Let's forget about the 'theta hat' terms because we are not interested in angular acceleration.
Now supposing the circular motion was a gravity orbit. Where do you see the inverse square law gravity term fitting into equation (4)? Does it go to the general acceleration term on the left hand side, or does it go to the r double dot term on the right hand side? David Tombe ( talk) 20:06, 2 May 2008 (UTC)
Steve and FyzixFighter, it would be a help if the two of you discussed this together and appointed a spokesman to ask me the questions.
Equation (4) tells us nothing until we know exactly what scenario we are applying it to and what the forces involved are. I asked FyzixFighter were he wanted to put the gravity force if it were a circular gravity orbit, and I didn't get a clear response.
Lets then deal with an easier situation. Let's deal with a weight being swung around on the end of a string. We use the symbol T to represent the inward tension. Can you please present me with equation (4) as per this scenario, showing me where you have inserted the tension T. David Tombe ( talk) 06:45, 3 May 2008 (UTC)
Steve, I'm going to ignore the issue of whether we talk about force or acceleration. We are talking about inertial forces here so it is quite irrelevant.
Now can we get to the key point. You are quite wrong in thinking that the v^2/r term is centripetal force. How could it be? How would a general expression for acceleration suddenly produce a centripetal term in conjunction with a Coriolis term? The parent inertial term vXω expands in two mutaully perpendicular components in polar coordinates. One is the Coriolis term and the other is the centrifugal term. In fact it is quite ridiculous to think that it could possibly be referring to the centripetal force.
Let's consider how that equation is used in orbital theory. The term that you think is a centripetal term is brought over to the left hand side to join the gravity expression. Hence gravity will have a negative sign and the term that you think is the centripetal term will have a positive sign. on the right hand side, we have r double dot.
So we have a second order differential equation in r.
If r double dot is zero, then the gravitational force inwards is exactly cancelled by the centrifugal force outwards.
If you are correct, it would imply that centripetal force is something that occurs naturally. That is not so. The gravitational force IS the centripetal force in this situation, and the v^2/r term is the centrifugal force. David Tombe ( talk) 03:22, 4 May 2008 (UTC)
David, I think I've come to understand a key yet subtle point of disagreement. This is an honest attempt to understand how you understand the physics; I think we might be disagreeing on how we define radial acceleration. So let me set the stage. This is a stationary frame described by polar coordinates. We have an object move in some arbitrary fasion in this frame, and whose position is defined by the coordinates and . In this case, what is the proper expression for the radial acceleration, defining the radial acceleration as :
Or do you disagree that the radial acceleration should even be defined as ? -- FyzixFighter ( talk) 04:41, 4 May 2008 (UTC)
FyzixFighter, I'm sorry but you're very badly mistaken here. The equation that I wrote out is the central force orbital equation. That is the equation that is used to solve central force orbital problems. I solved many a complex problem using that equation.
The equation which you have used is a general acceleration equation derived from a position vector using vector calculus theorems and notation. Whereby I have always been impressed by the amount of information that this equation reveals, we can not allow a quibble about terminologies to alter the reality of the final central force orbital equation.
Your equation effectively exposes the fact that centrifugal force is inherent in straight line motion as viewed from polar coordinates. In fact, I ought to draw the attention of Brews to that point.
But there is no further argument regarding the form of the orbital equation. One side contains a second order time derivative of the radial distance and the other side contains an inward gravity force and an outward centrifugal force. You can call that second order time derivative whatever name you like. But in circular orbits, it will be zero.
And if you try messing around with the signs in the orbital equation, you will no longer have the orbital equation. If you want a conic solution, then that is the equation. David Tombe ( talk) 08:56, 4 May 2008 (UTC)
Plvekamp has finally responded,
From a rotating frame, the person is accelerating toward the car door.
Now the whole introduction is about centrifugal force which it claims is a force only ever viewed from a rotating frame.
I added a line saying that in situations of co-rotation, an object accelerates radially outwards.
Plvekamp erased this sentence on the specious grounds that this true fact didn't agree with the references.
What references was he talking about? Was he referring to all the references that were wheeled in to enforce the fact that the term 'fictitious' is widely used?
So can we conclude that Plvekamp sacrificed reality in order to comply with the references?
If a centrifuge proves to us that centrifugal force is a real and absolute effect, but the references tell us that this shouldn't be so because the force is question is only a fictitious force, then rather than question the references, we should be better to erase the sentences that draw attention to these inconvenient truths.
Plvekamp, it's about time that you opened your eyes a bit to what's going on in the world around you. David Tombe ( talk) 20:17, 2 May 2008 (UTC)
If you weren't denying those phenomena, then why did you erase mentions of them in the introduction? David Tombe ( talk) 06:27, 3 May 2008 (UTC)
I will no longer respond to your goading, David. Plvekamp ( talk) 12:12, 3 May 2008 (UTC)
David, is there any conceivable argument that might convince you that you are wrong, or are you simply committed, as is suggested by your most recent response above, to promulgating the WP:TRUTH as you see it?
The reason everyone else in this discussion appears to disagree with you, whilst all agreeing with one another, is that they are describing the apparent phenomenon of "centrifugal force" in rotating non-inertial frames in terms of inertial effects within standard Newtonian physics. This has been the standard physical interpretation of this phenomenon for several centuries, and is not likely to change. On reviewing this very lengthy discussion, I can see that this has been explained to you over and over in many different ways, carefully and politely, by numerous different people, with only you taking the dissenting position.
You are unlikely to succeed in ever getting your views represented in the article if you continue in this way. Here's why.
Wikipedia is a tertiary source; it summarizes the information in secondary sources, such as peer-reviewed scientific papers, physics textbooks, and other texts written by qualified physicists. It is not a mechanism for determining the WP:TRUTH; we accept that people disagree about just about everything, and we try to reflect this in our articles. For this reason, we have a set of ground rules for editing here which explicitly try to avoid determining truth here on Wikipedia, relying instead, wherever there is controversy, on restricting ourselves to opinions which can be attributed to external, verifiable, reliable sources.
If you want to change the article, and have your changes kept, you must, like every other editor here, abide by Wikipedia's basic ground rules, namely
Furthermore, we have another requirement: that editors conduct themselves according to our civility policy. Statements that imply that other editors are acting in bad faith, lack intelligence, or are conspiring against you, go against that policy. Repeated breaches of the civility policy may result in accounts being blocked from editing.
Unfortunately, a personal conviction, no matter how strong or sincere, that your views are the WP:TRUTH does not override these policies and guidelines. -- The Anome ( talk) 21:53, 2 May 2008 (UTC)
Anome, you know perfectly well that the edits that I made yesterday were not about ideas that are contrary of current theory. I drew attention to the actual acceleration that occurs outwards when an object co-rotates with a rotating frame. An example would be a passenger in a car getting swung to the side door as a car goes round a corner.
You know fine well that that was not a controversial sentence. You are misrepresenting the situation by continuing to imply that I was trying to insert controversial clauses into the article.
Plvekamp, PeR, and FyzixFighter removed that sentence because they are uncomfortable with the truths inherent in it. Their actions were essentially vandalism which you could have prevented but you chose not to do so. David Tombe ( talk) 12:39, 3 May 2008 (UTC)
Anome, I'm not going to bother. That wasn't the issue. I have no intention of going to search for a citation for such a trivial and undisputed fact. It wasn't erased because there was no citation. That was just the cover story. It was erased for other reasons, and the point was proved.
By the way, I am watching your efforts to re-word the introduction. Note what Woodstone says over on the Coriolis force talk page.
There seems to be a school of thought that is saying that the term fictitious actually means that it refers to a mathematical term which comes into effect only in the accelerated frame (in this case, the rotating frame) as an alternative way of describing real effects.
I don't think that that is the universal interpretation of the term fictitious. I think you will find that some of the editors here will try and slowly but surely graft it back to the extent that it literally means that the effects can only be viewed in the rotating frame.
If what you are saying is true, RRacecarr and PeR wouldn't have cocnsistently reverted my removal of the word 'apparent' on the Coriolis page.
I would perhaps tend to agree with your amendments if I am interpreting you correctly. You are saying that these effects are real but best dealt with mathematically by what we term 'fictitious forces'. If that is so, I think that you will also agree with me that the term 'inertial force' is infinitely superior. David Tombe ( talk) 15:28, 3 May 2008 (UTC)
PlveKamp, I think that the big problem that we are up against is that the modern textbooks are pushing these mathematical transformation equations in a way which disguises a very important difference between two completely different situations. These two different situations are described in the famous Bucket argument.
My natural inclination would be to view centrifugal force as a convective force. In other words it is a force which comes into existence at right angles to the direction of motion of a particle moving in a curved path. And that the effects, which are now described to be real, in the introduction are only effects which have come into existence BECAUSE the object is engaged in a curved path motion.
At the moment, the introduction is now admitting to real effects. It was never actually an issue in the edit war about whether or not these real effects could be explained in different ways in different frames.
Initially, I was arguing against a party which were adamant that these effects were entirely fictitious and could only be viewed in the rotating frame.
Finally by pushing the issue of the centrifuge which clearly disproves such a fictitious outlook, the reality of these effects was finally acknowledged. However, in a sense it is being whitewashed by pointing out that centrifugal force is a fictitious force by virtue of the fact that it is merely an appropriate way of describing effects in a rotating frame which could be described by other means in the inertial frame.
This is an improvement. But it still lacks the most important clause of all.
That clause is that centrifugal force is about real radial effects which come about BECAUSE of curved path motion.
Unfortunately the interpretation of the maths that these guys are pushing is indeed the official line. I did it myself many years ago in applied maths and I can confirm that.
The maths itself is correct. But they are interpretating it such as that ω^2r means that the centrifugal force acts on any body in a rotating frame.
I am adamant that the ω term is telling us that it only applies to objects that themselves have that ω. And the fact that a centrifuge only works for co-rotation would tend to back that idea up.
It would seem however that what they are preaching is indeed what is being preached in the universities.
So there's not really very much that anybody can do to help the situation. The first line in the introduction messes it all up from the outset.
I would have liked a line that drew attention to the absolute reality of co-rotation situations. That is essentially what the recent stage of the edit war was about.
But at the end of the day, there is no doubt that fictitiousism is in the ascendency at the moment.
I have just heard that sometime in the early 1950's the textbooks on orbital theory switched the centrifugal force term in the equations into centripetal force.
So really the problem is too far gone now for anybody to be able to do anything about it. David Tombe ( talk) 17:53, 3 May 2008 (UTC)
Brews, in Cartesian coordinates, the centripetal force shows out alone as you say. I am totally familiar with the derivation. We take two velocity vectors on the arc of the circle and make a vector triangle. This leads to an inward pointing acceleration of value v^2/r.
But you are overlooking something very important. This centripetal acceleration is with reference to the straight line path that would have occured had the centripetal acceleration not been there.
This straight line path is in fact inertia. Now do that exact same vector triangle again using the straight line path referenced to the exact same point. This time you will get an outward acceleration of v^2/r. In other words, the centrifugal force is implicit in the inertia.
In polar coordinates, we only consider the radial direction, and in that case inertia becomes centrifugal force. David Tombe ( talk) 06:25, 3 May 2008 (UTC)
Brew's, if you can derive centripetal force, just repeat that derivation, but this time instead of considering the velocity vector as having changed its direction in relation to the Cartesian frame, consider it to have changed its direction outwards in relation to the radial vector. You will get exactly the same expression outwards and it applies to straight line motion in the Cartesian frame. Inertia IS centrifugal force.
There is another way of looking at it. Consider the general central force orbital equation. Gravity and centrifugal force combined yield a conic section. In the extreme case of when the gravity is negligible, we get a highly eccentric hyperbola. This is effectively a straight line.
In other words, centrifugal force acting alone leads to a straight line.
Centrifugal force in conjunction with centripetal force leads to a circular motion.
Conclusion. Centrifugal force is always there in the outward radial direction in circular motion, but in the Cartesian frame it is masked as 'inertia'. David Tombe ( talk) 15:12, 3 May 2008 (UTC)
No Brews, let's consider the case when there is no centripetal acceleration and the particle moves in a straight line.
Now do that same vector triangle again referenced from the centre of that same circle that you would have used if there had been centripetal force.
This time you will discover a net outward direction changing acceleration.
In other words, the centrifugal force is there all along but disguised in the straight line motion which is inertia. It doesn't show up in the Cartesian analysis. But it is there.
Now go into polar coordinates and if we have circular motion, the centripetal force inwards will be exactly balanced by a centrifugal force outwards.
Consider an elliptical orbit. Consider the stage when the object is closing in on the centre. According to you this closing in is a consequence purely of the one and only inward acting centripetal force. And based on the expression for gravity (inverse square law), you might think that the fact that the gravity is getting stronger as it gets closer, would mean that it should spiral in even more so.
But it doesn't. At some stage of the orbit, it starts to go up again. What is that radially outward force that suddenly overcomes gravity? David Tombe ( talk) 17:28, 3 May 2008 (UTC)
Brews, if we treat the straight line path from a Cartesian perspective, then the acceleration is zero if it has constant speed.
But if we treat it as measured radially from a fixed point, then it reads a centrifugal acceleration outwards of v^2/r.
Imagine an object going in a straight line with constant speed in the Cartesian frame. Imagine a lamp post which is not on its path.
At some stage the object will be getting progressively closer to that lamp post. Then a point of nearest distance will be reached and the object will then begin to get further away. If we consider the distance between the object and the lamp post, the second time derivative of that distance will be v^2/r away from the lamp post, where v is the component of the actual speed that is perpendicular to the radial vector. In other words, the maximum centrifugal force will occur at the point of nearest approach.
This is a central force orbit. The lamp post exerts negligible gravity and so the solution is a highly eccentric hyperbola which is efectively a straight line.
That is inertia and it is centrifugal force too. David Tombe ( talk) 18:46, 3 May 2008 (UTC)
Brews, in the scenario that I have given you, the direction of the position vector will be constantly changing and so it will be accelerating when viewed in that coordinate system. David Tombe ( talk) 06:16, 4 May 2008 (UTC)
Wolfkeeper, if you have failed to see the link between Kepler's law of areal velocity and the "2 times r dot theta dot" term in the tangential component, which is Coriolis acceleration, then it would appear that you really do have some fundamental misunderstandings of this topic. There is no angular acceleration involved in central force orbital theory.
While you are attempting to back up Steve and FyzixFighter, you are actually saying things that contradict them.
I suggest that the three of you get together to appoint a spokesman so that you can speak with a united voice and we can then bring this argument to a definite conclusion. David Tombe ( talk) 09:54, 3 May 2008 (UTC)
Plvekamp, this is what I mean by the whitewash. This line here sums it all up,
The results obtained by considering these pseudo-forces to be "real" within the rotating frame are identical to those given by calculations made in the inertial frame without them.
That line totally fails to address the fact that the most important aspects of centrifugal force, such as getting thrown to the side door of a swerving car, actually arise BECAUSE of the rotation.
The whitewash line evades that issue totally and acts as if we have these effects that just happen to be going on and we have different ways of describing them in different frames of reference. It misses the entire point of what centrifugal force is about in the name of trying to reconcile two conflicting viewpoints over whether centrifugal force is real or fictitious. David Tombe ( talk) 18:04, 3 May 2008 (UTC)
This would not have been a problem if the article had not defined the centrifugal farce as fictious. So you need to say real, to distinguish it from fictious. Fictious means not real or imaginary. Pseudo means false. The confusion is on the part of the people who use these terms to discuss physics. I say again that the editors, and this means Mr Anemone, you dont understand physics, and this article on the centrifugal farce should be deleted from wikipedia since you will never get the physics right in this discussion.
72.84.70.6 (
talk) 20:28, 3 May 2008 (UTC)
Anome, You've missed the point entirely. Centrifugal force is an effect which comes about BECAUSE of rotational motion. Spin an object and a centrifugal pressue will be induced.
It has got nothing to do with how we describe it in different frames of reference.
At the moment, the article begins by stating that centrifugal force is fictitious and that it is only apparent in rotating frames.
The article then continues by contradicting this and stating that there are real effects but that they would be there anyway whether there is rotation or not. Wrong.
The article then mentions that the centrifugal force that involves actual outward motion, which would be what people have in mind when they look up an article on centrifugal force, is not the centrifugal force that is dealt with in this article.
And it finally ends by stating that the whole matter is very confusing.
Anybody reading this introduction would simply say 'what?'. And they would be less wise about centrifugal force than before they read it.
I'm going to put in a qualifying clause regarding the necessity of the real effects to be induced by rotation. If this clause is deleted, which I am sure it will be, then I can only conclude that the person who deletes it has got absolutely no comprehension of the topic whatsoever.
In fact if I had been the one that had put in what you put in, it would have been deleted already because these people are not even happy with the idea of real effects at all.
But when it was deleted, somebody who would have deleted it if I had been the author, actually restored it.
It is clear from observing the activities on this page, that there is a certain group who revert according to who made the edit, rather than what the edit involved. David Tombe ( talk) 03:47, 4 May 2008 (UTC)
No Wolfkeeper, the Coriolis force does not occur in the natural state of affairs, but the centrifugal force does. This is a direct consequence of Kepler's law of areal velocity which eliminates the Coriolis force and the Euler force from planetary orbital motion. Everyday straight line motion is a special case of planetary orbital motion. David Tombe ( talk) 15:43, 5 May 2008 (UTC)
Dbachmann, the confusion is not all mine. The confusion is all yours for failing to be able to see that actual rotation induces real radial effects, whereas no effects at all are induced on a stationary object whether it is observed from a rotating frame of reference or not. David Tombe ( talk) 09:18, 5 May 2008 (UTC)
Does it only appear that his bones are broken? 119.42.68.141 ( talk) 10:09, 9 May 2008 (UTC)
From the McGraw Hill Dictionary of Mathematics and Physics centrifugal force: (1) An outward pseudo-force, in a reference frame that is rotating with respect to an inertial reference frame, (2) The reaction force to a centripetal force. —Preceding unsigned comment added by Denveron ( talk • contribs) 04:48, 4 May 2008 (UTC)
One of the requirements of scientific thinking is that the terms used in science have a definite and clear meaning and that there is an economy of terms used. This is not the case in modern physics which has multiplied a profusion of confusing and ambigous terms to discuss centrifugal force. There was no problem with this definition for several hundred years. Yet now, one can not read a physics book without being subjected to a multitude of ambigous confusing and absurd definitions that basically are meaningless metaphysical entities which contribute nothing to the understanding of the physics involved. The fact that wikipedia can not make sense out of this centrifugal farce demonstrates the useless aspect of these absurd terms. Wikipedia editors dont know what these terms mean and they cant explain them here, so you should call this article the centrifugal farce. The article should be entirely deleted since you will never get it right. 72.84.66.108 ( talk) 15:04, 4 May 2008 (UTC)
Sheffield Steel, I have been advocating that very point. There is no need to mention rotating frames of reference at all. It merely provides a mechanism within which to perform conjuring tricks with the maths. It obscures the underlying reality of the fact that centrifugal force only occurs when actual curved path motion happens.
In relation to your reply to 72.84.66.108, can you please tell us all exactly what outdated and incorrect ideas you have in mind. From what I can see, he is saying the same as me, which is that we need to have co-rotation in order for centrifugal force to occur. Is that an outdated and incorrect idea? David Tombe ( talk) 09:15, 5 May 2008 (UTC)
What I got from the above pages of chatter was that the Introduction was too geeky - not everybody is a mathematical aficionado. So to please David and provide a bit broader attack on the subject than "coordinate transformations" I rewrote the first few paragraphs. I know it's presumptuous of me, but somebody said it's easier to revise something than to look at a blank page. So go for it. Brews ohare ( talk) 06:19, 4 May 2008 (UTC)
You must be joking. The entire article is a morass of confusion, and you are complaining about a small attempt at clarification. The article is nonsense as it stands and the attempts to sort out the confusion by imposing more rigorously defined nonsense is a joke. 72.84.66.108 ( talk) 16:52, 4 May 2008 (UTC)
This subsection should be deleted. What is not a rant is either repetitious or unsupported. Brews ohare ( talk) 16:04, 4 May 2008 (UTC)
'Rotating frames of reference' only clouds the entire issue. The key point which is being consistently swept under the carpet is the fact that the transformation equations only apply to co-rotating objects. If there is no co-rotation, then nothing happens.
It is clear that this entire mess is a result of total denial of this fact. I have looked through the edits of the last day and I can see that Virginia anonymous has been trying to push this same point, but that just as when I do it, it gets deleted immediately.
It seems to me that it is much more important to all of you to emphasize trivial facts, such as 'These real effects can also be described equally well in an inertial frame', than to mention the most important fact of all which is that these real effects are actually induced by the rotation itself.
Recently we saw the parent force for both the centrifugal force and the Coriolis force. It takes the form vXω.
The manner in which the editors here have been trying to present this very real inductive effect would be analgous to trying to explain electromagnetic induction as follows,
As viewed from the frame of reference of a rotating bar magnet, an electric current is seen to be induced in a nearby electric circuit. This effect can be equally well described from the inertial frame.
I'm sure that you would all agree with me that it would be the height of nonsense to explain electromagnetic induction like that because it misses out on the most crucial aspect of all which is that the induced electric current occurs BECAUSE the bar magnet is rotating.
You are all doing exactly the same in this article. You are all denying the underlying induction aspect that is caused by absolute rotation.
So if you guys are going to insist on deleting all references to the importance of co-rotation, then you will all remain confused for a very long time. David Tombe ( talk) 08:58, 5 May 2008 (UTC)
No Wolfkeeper, it doesn't. A stationary object in the inertial frame experiences no physical effects by virtue of being observed from a rotating frame. David Tombe ( talk) 15:19, 5 May 2008 (UTC)
I notice that there is now a section entitled 'Is centrifugal Force Real?'.
Well at the beginning of the edit war, I mentioned that Newton, Maxwell, and Bernoulli had believed it to be real. I even provided references. But that true fact was instantly deleted. The 'Fictitious party' are not even comfortable with any mention of the fact that centrifugal force was once believed to be real by the great masters of physics.
You can read this interchange with PeR at the beginning of the edit war and make up your own minds,
David, The centrifugal force was never considered to be real by Newton, Maxwell, or Bernoulli. If you want to put a statement like that you need to cite a source. Specifically you need to cite a source that says "the centrifugal force was considered to be real", or something very similar to that. If you read a text by, say Maxwell, and interpret that as him saying that the centrifugal force is real, that is still original research, since it is your interpretation of what he says. --PeR (talk) 17:16, 20 April 2008 (UTC)
Reply: Admissibility of Evidence
PeR, I think that you are going to have to repeat yourself. We need to get something straight here regarding the issue of admissibility of evidence. You declared that centrifugal force was never considered to be real. You further went on to state that if I were to produce any quotes from Newton or Bernoulli which indicated that they believed that centrifugal force was real, that this would not be deemed to be admissible evidence on the grounds that it would be my own original research. Here is a quote from Bernoulli out of the ET Whittaker book on the history of aethers.
"The elasticity which the Aether appears to possess, and in virtue of which it is able to transmit vibrations, is really due to the presence of these whirlpools; for, owing to centrifugal force, each whirlpool is continually striving to dilate, and so presses against the neighbouring whirlpools."
And here is a quote from Maxwell's paper 'On Physical Lines of Force',
"The explanation which most readily occurs to the mind is that the excess of pressure in the equatorial direction arises from the centrifugal force of vortices or eddies in the medium having their axes in directions parallel to the lines of force"
And you are trying to tell me that this is not evidence to suggest that Bernoulli and Maxwell believed that centrifugal force was real?
YES! I am trying to tell you that this is not evidence to suggest that Bernoulli and Maxwell believed that centrifugal force was real. However, if you don't want to accept this you don't have to. Just don't write anything in the article. If you do want to write something like that then you must (and here I am repeating myself, as requested) cite a source that says "the centrifugal force was considered to be real" or something very similar to that. If you read a text by, say Maxwell, and interpret that as him saying that the centrifugal force is real, that is still original research, since it is your interpretation of what he says. --PeR (talk) 19:42, 21 April 2008 (UTC)
reply: PeR, There is a controversy about whether or not centrifugal force is real. The official position today is that it is not real. The current introduction is abominable because it tries to fudge the issue by pretending that there are two centrifugal forces. One for the realists, and one for the fictitiousists. This is an extreme case of ecclecticism. The current introduction cannot remain because it is a total disgrace.David Tombe (talk) 08:02, 21 April 2008 (UTC)
He replies. You misinterpret what it says. However, the fact that you don't understand it is evidence that it is not clearly enough written, so I agree that it should be rewritten. --PeR (talk) 19:42, 21 April 2008 (UTC)
David Tombe ( talk) 09:33, 5 May 2008 (UTC)
Brews, when actual co-rotation occurs, the centrifugal force is (1) real, (2) radial, and (3) it can be observed from all reference frames. It is an absolute effect.
When there is no co-rotation, then there is nothing. There is no centrifugal force. There are no physical effects in any reference frame. David Tombe ( talk) 15:17, 5 May 2008 (UTC)
David, when your talking about what "a person sit in a car driving in a circle" experiences, you are implicitly specifying a frame of reference. Namely, what a person experiences can only be described in a co-moving frame. Such a frame is typically non-inertial and will thus contain psuedoforces (or however one wishes to call them) from the perspective of this observer/person these forces are very much real. As you state the person feels himself pushed towards the outward door. An other observer will understand this diffently. An observer from an inertial frame will see the person in the car being forced to move in a circle by force exerted on him by the car.(TimothyRias (talk) 14:32, 5 May 2008 (UTC))
If you want to argue from ancient references, please take a look at Newton's Principia Book 1 and Euler's Mechanica Chapter 5, in which curvilinear motion is discussed. Neither author finds it necessary to use centrifugal force; but centripetal force is ubiquitous. Why is that? (Clue: the analysis in both cases uses inertial frames of reference.) Additionally, why do modern physicists also mention centrifugal force in their articles, but yet, none of them here on Wikipedia agree with your interpretation? There must obviously be a cabal, since you have the WP:TRUTH. Plvekamp ( talk) 15:49, 5 May 2008 (UTC)
David, instead of just stating that people are completely confused, you might try and use actual arguments. Our at least try to understand other people's arguments. And actually the centrifugal force induced on the man in the car is only perceived in the co-moving frame. And observer in an inertial frame will only perceive one force acting on the man in the car and that is the force exerted on the man by the car. (well if you would also count gravity that would be two, but that is really beside the point) ( TimothyRias ( talk) 20:56, 5 May 2008 (UTC))
David, you are missing my point. Sure the seat in the car is exerting a force on the person in the car causing him to follow its movements. My point was that if viewed from an inertial frame this is the only force acting on the man even when going around a corner. When the car is driving around in a circle at constant speed the force exerted on the man by the car is completely radially inward. (I'm neglecting gravity here for the moment for convenience of speech) ( TimothyRias ( talk) 07:48, 6 May 2008 (UTC))
No David he would not! If what you say would be true, then the person on the street would see the person in the car make a curve in the opposite direction of the car. We all know this to be false, the person will move in a straight line as seen from the street. ( TimothyRias ( talk) 08:18, 6 May 2008 (UTC))
No Timothy, the person in the street sees the passenger move in a straight line in the Cartesian frame, but he also sees the passenger moving out radially towards the side door in the rotating frame. He can see both frames at once. David Tombe ( talk) 08:44, 6 May 2008 (UTC)
Timothy, I was only describing it all in one frame at a time. The centrifugal force occurs radially when the passenger is subjected to a tangential motion. You can consider that effect real or fictictious. It's up to you. But one thing is sure. It only occurs when the passenger has a tangential velocity. It does not occur on objects that are not co-rotating with the car. David Tombe ( talk) 13:32, 6 May 2008 (UTC)
Yes, Timothy. And the ball would also have centrifugal force in relation to the centre point of the car's circular motion. The actual factor that induces centrifugal force is 'tangential velocity relative to a point in space', and the centrifugal force is a radial force measured relative to that point.
Co-rotation in a rotating frame of reference is only one particular scenario that brings about centrifugal force. It is not the most general scenario. When I said above It does not occur on objects that are not co-rotating with the car., I was specifically referring to stationary objects. David Tombe ( talk) 04:25, 7 May 2008 (UTC)
This is copied from above:
--- Brews, when actual co-rotation occurs, the centrifugal force is (1) real, (2) radial, and (3) it can be observed from all reference frames. It is an absolute effect.
When there is no co-rotation, then there is nothing. There is no centrifugal force. There are no physical effects in any reference frame. David Tombe ( talk) 15:17, 5 May 2008 (UTC)
Wolfkeeper, You have changed the context. In my original discussion with Brews, I was saying that in straight line motion in the inertial frame, centrifugal force is built into that motion in the form of inertia. If we measure the second order time derivative of radial distance from a fixed point, we will get v^2/r where v is the component of the velocity that is perpendicular to the radial line.
You tried to cloud the issue by introducing Coriolis force. Coriolis force is not involved in that scenario. Kepler's laws have eliminated Coriolis force from planetary orbital theory.
You then went on to introduce a rotating frame of reference scenario which would indeed involve fictitious tangential effects. David Tombe ( talk) 07:49, 6 May 2008 (UTC)
Lets derive those equations shall we. Lets consider a particle moving in a rotating frame rotation with angular speed . At any time the kinetic energy of this particle will be given by . The corresponding action is By the action principle the variation of this should vanish
This implies the equation of motion:
which is equivalent to the transformation formula present in the article. From this derivation it is manifest that can take any vector value, and is independent of . In particular, is not radial as you have been claiming. ( TimothyRias ( talk) 09:07, 6 May 2008 (UTC))
I did no such thing. I subtracted a vector and then took the norm. The vector I subtracted has no relation with whatsoever, it is just a position based factor having to do with the fact that we are describing the physics in a rotating frame. Really, start listening to the people with actual degrees in physics that understand what they are talking about. ( TimothyRias ( talk) 09:26, 6 May 2008 (UTC))
Timothy, Yes, I see what you have done now. It is indeed an arbitrary velocity. But I can't see how you have linked that arbitrary velocity to the velocity term in the transformation equations. I simply don't follow your arguments above. There is absolutely no need to introduce that kind of mathematics to the problem. You are beginning at a very strange point. You begin with the general expression for kinetic energy for a particle in a rotating frame of reference. Correct. But then you introduce a potential energy term that is not needed. After a few manipulations which I simply don't follow, you conclude that it all implies the relevant transformation equations. You would need to show what all the maths terms mean at each stage of the derivation. Those same equations can be derived much more transparently in such a way that we can clearly see that the velocity term has to be the radial velocity. Why did you choose to introduce all that unnecessarily complicated maths above? There was absolutely no need for it. The point has been proved with a much more simple maths. So it can hardly be disproved just by introducing more complicated maths. David Tombe ( talk) 13:25, 6 May 2008 (UTC)
To me this one of the simplest ways to derive the EoM in a rotating frame. You haven't provided any "proof" of your statements. Here I have provide a simple proof that transparently disproves your claim. If this already goes above your head, you might want to reconsinder meddling in something that you clearly do not understand completely. ( TimothyRias ( talk) 14:05, 6 May 2008 (UTC))
Timothy, Hamiltonian and Lagrangian have got nothing to do with it. Your error lies in your interpretation of the expression for kinetic energy. In fact you don't even need to involve kinetic energy. We only need to look at the particle velocity. The moment I see the ωXr expression, I can tell instantly that you have routed the velocity through a point on the rotating frame. ωXr is the tangential component of the particle velocity in the limit. And because it is in the limit, the other component must be radial. You cannot escape that fundamental reality which lies right at the heart of those transformation equations. What you did above was to cloud that reality up with a whole package of Hamiltonian, and integrals, and potential energies. David Tombe ( talk) 09:43, 7 May 2008 (UTC)
Timothy, the expression is absolutely dependent on it applying to the limit. If we consider the velocity vector split into two larger components, then none of those components are ωXr.
On Coriolis force, it is not involved in Lagrange points or stability because there is no curl in the gravitational field. And in your books, it cannot be involved in stability because it is only a fictitious force.
This is another example of your tactic which is to move the discussion into unnecessarily complicated zones such as Lagrangian, Hamiltonian, and the three body problem which has never been satisfactorily resolved. It is actually a deceptive tactic used by alot of people who have been proved wrong in the simple arena. Move the debate into the dark dirty jungles and cloud the whole issue. David Tombe ( talk) 11:46, 7 May 2008 (UTC)
Timothy, your six line proof fails on the first line before you even reach all the fancy Hamiltonians, integral signs, and potential energy terms.
Your proof fails at the point where you assume that if one component of the particle velocity is ωXr, that the other component has got arbitrary direction. The much more basic and less pretentious vector calculus that is used to derive the term ωXr insists that this term only applies when it is the tangential component of the particle velocity in the limit that this component tends to zero. It is the very same calculus that is involved in differentiating the position vector to obtain the general acceleration equation in radial/polar coordinates. We differentiate r and we end up with ωXr in the tangential direction and r dot in the radial direction. Your big problem is that when you were first shown the derivation of the rotating frame of reference equations, you never questioned that detail. You just accepted what you were told. Now that you have seen that there are restrictions of applicability which you had never thought about before, you are just digging in because you entered this argument without first checking your facts. Hence you are trying to cloud the whole issue by introducing high powered maths topics like Hamiltonians, and Lagrangians, and best of all, the ever controversial three body problem. None of these complications are necessary in order to analyse a simple vector triangle of velocity for a simple one particle motion with no potential energy terms. David Tombe ( talk) 15:58, 7 May 2008 (UTC)
Timothy, no you cannot. You are free to choose whatever value of velocity you like. But if one of its components is described by the expression ωXr, then it must necessarily be the tangential component, and therefore the other component must be the radial component. David Tombe ( talk) 06:34, 8 May 2008 (UTC)
Timothy, you can split the particle velocity into as many components as you like. But if one of those components is ωXr then the other component must be radial. This follows directly from the transport theorem. ωXr is the tangential component of the particle velocity in the limit. Hence the other component must be radial. You are ignoring a restriction that is built into the derivation. David Tombe ( talk) 10:09, 8 May 2008 (UTC)
No Timothy, it means that the equations only apply to particles that are co-rotating with the frame, because in those equations ω will represent both the angular velocity of the frame and the particle. If you choose ω not to be the angular velocity of the particle, then you cannot derive the transformation equations. There will be no physical linkage. v must be routed through the tangential term ωXr which is common to both the frame and the particle. 119.42.65.152 ( talk) 13:30, 8 May 2008 (UTC)
Timothy, let's see you deriving the transformation equations using a particle with an angualr velocity that is different from the angular velocity of the rotating frame? 119.42.68.141 ( talk) 10:14, 9 May 2008 (UTC)
, where .
Thus the position of the particle in the rotating frame is: . Hence
where we used that for any vector and in the last line that and Newton's second law in the inertial frame. The first statement is easy to check if done explicitly. The second statement basically is just line four of the argument. Here the derivation of the transformation formula if is not the angular velocity of . ( TimothyRias ( talk) 14:06, 13 May 2008 (UTC))
No Timothy, this is just another elaborate deception. The same vector triangle applies. You can't claim that the particle in question has a different angular velocity from the rotating frame simply by stating this to be the case before the derivation begins.
The derivation ensures that the angular velocity of the particle and the frame must be the same because as soon as we end up with one component of velocity given by rXω, then it must be tangential. And as such, the other component then has to be radial. 118.175.84.92 ( talk) 16:26, 13 May 2008 (UTC)
FyzixFighter, the orbital equation is found widely throughout applied maths textbooks. It takes the form,
-GM/r^2 + v^2/r = r double dot
It solves to give an ellipse, parabola, or hyperbola.
The inward -GM/r^2 term is the centripetal force. The outward v^2/r term is the centrifugal force. They both work together in the radial direction in tandem with each other.
I have been accused by two administrators of introducing unverified material by virtue of mentioning this information. That shows me that the editors that are dominating this page know very little about the subject matter. David Tombe ( talk) 08:01, 6 May 2008 (UTC)
FyzixFighter, Let's leave names and terminologies out of it altogether. We have a second order time differential for the radial distance from the focus. Call it acceleration if you like, or don't call it acceleration if you don't like. That second order differential term is equated to two other terms. One is an inward acting GM/r^2 term. Call it gravity if you like. Don't call it gravity if you don't like. We also have an outward acting v^2/r term. Call it whatever name you like. But one thing is sure. Both of these terms are very real. They are both radial, and they both act in opposition to each other. That's what planetary orbital theory is all about. It could be correctly said that one of these terms is the centripetal force and the other is the centrifugal force. That second order differential equation is difficult to solve, but it has been tackled over the last couple of hundred years by the top applied mathematicians and there are a number of ways of solving it. I have seen at least two methods. The one that I actually had to learn for my exams involved substitution and we ended up with a new variable U. The derivation went for at least a couple of pages. Maybe even three or four pages. The final result is the geometrical expression for a conic section. There will be two arbitrary constants in that expression. One is the semi latus rectum and the other is the eccentricity. When we know the initial speed, position, and direction, we can work out what these two constants are and that tells us the exact shape of the conic section. If the eccentricity is less than 1 we will have an ellipse. A circle is a special case of the ellipse. If we have an eccentricity that is equal to 1, we get a parabola. In other words, the object has escaped from closed orbit. If we get an eccentricity greater than 1, we will have a hyperbola. If you want to study this topic in more detail, I advise you to first of all brush up on the geometry of conic sections in polar coordinates. After that, you should find the orbital equation in any good undergraduate classical mechanics textbook. Goldstein probably has it. Here is another point of interest. There is a theorem which dircetly links Kepler's law of areal velocity to the tangential terms of the general acceleration vector which you quoted. That gets rid of both the Euler force and the Coriolis force. Gravity orbits are a zero curl affair. To have Coriolis force, we need a curl. But let's get back to the original point. Thanks to SCZenz's comments to the anonymous, I now know that my mathematical reasoning does not need any citations. For a circular motion to occur, the second time differential of the radial distance must equal zero. Hence the sum of v^2/r and the inward centripetal force must equal zero. In the artificial circle, which is purely an artifact and doesn't involve any centrifugal pressure at all, your team have been arguing that the outward centrifugal force v^2/r is counterbalanced by an inward acting Coriolis force. This is nonsense on a number of counts. The Coriolis force never acts radially. The Coriolis force and the centrifugal force are always mutually perpendicular. Do you remember the acceleration expression which results if we act directly on v? It is vXω. That is the parent force of both Coriolis and centrifugal before it gets expanded into two mutually perpendicular components. Also,even if your team are correct and we can make the Coriolis force act radially inwards, then the result will be twice that of the centrifugal force. So the second order time differential of the radial distance will not be zero. Hence we can't have a circular motion. Those transformation equations are only designed to deal with actual rotation. To invoke the Coriolis force we need a physical curl such as we get in hydrodynamics when an element of a rotating fluid moves radially inwards (or outwards) within itself. David Tombe ( talk) 04:55, 7 May 2008 (UTC)
Some remarks:
( TimothyRias ( talk) 09:09, 7 May 2008 (UTC))
The current introduction ends with the sentence, Colloquially, the term "centrifugal force" is sometimes also used to refer to any force pushing away from a center; this article discusses only the centrifugal force related to rotating reference frames. So where is the page on colloquial centrifugal force? That's the page the readers want. This sentence is effectively the same as saying, If you are looking for centrifugal force, you have come to the wrong page. David Tombe ( talk) 06:12, 7 May 2008 (UTC)
Probably everything to do with centrifugal force. David Tombe ( talk) 11:32, 7 May 2008 (UTC)
I want to see the peer reviewed proof that justifies the statements made in the main article. These need to be peer reviewed journal articles or reccomendations from a physics education committee and cited in the main page. As far I can determine, there is no peer reviewed, critically examined proof of what is said in the main article. Citations which refer to sources that repeat or draw conclusions from other unproved sources are not acceptable. I want to see the actual real proof, not hearsay that it exists in theory. 72.64.51.14 ( talk) 16:03, 7 May 2008 (UTC)
Thank you. As I understand it, you are officially stating that Wikipedia does not have a peer reviewed journal paper or physics education committe report to validate what you state in the main article. Therefore, I demand that you accept Mr Tombe's edits as valid edits, since you have failed to prove him to be wrong. He has produced textbook citations which back up his position, while you have produced nothing to validate your opinions. Evidently Wikipedia policy has failed in this case to produce the required proof to support the claims made in the main article. I insist that you correct the mistakes in this article, and allow Mr Tombe to make edits to this article. You have totally failed to prove him to be wrong and your actions and behavior are certainly objectionable in this matter, as you have behaved unfairly and rudely to him. You also need to correct these and apologise to him officially. 72.64.51.14 ( talk) 21:40, 7 May 2008 (UTC)
FyzixFighter, I refered you to Goldstein's Classical Mechanics. There, as well as in many other applied maths textbooks, you will see the orbital equation which I described to you above. That equations makes it clear that the second time derivative of radial distance is only zero when we have two opposing forces cancelling each other out, one of which takes the form v^2/r outwards.
Anome never demands citations from other peoples' edits. He only demands citations for my edits. And when I give citations, he ignores them and continues to demand citations.
When I give maths reasoning, I get the red card held up against me. When Timothy Rias gives maths reasoning, SCZenz comes in to say that it's all fine. David Tombe ( talk) 06:29, 8 May 2008 (UTC)
Thank you gentlemen. You have again failed to meet the minimum requirement of proof in science. That is a peer reviewed journal article that has been reviewed, discussed, debated, and validated. You have no physics education committe report that produces reccomendations, resulting from physics education studies, and justified by a peer reviewed journal paper that scientifically validates that what you write in the main article is correct. You are basically citing only opinion, and that opinion is not validated by any scientific procedure that I can determine. Therefore your main article claims are false and invalid and Mr Tombe has very right to dispute them and insist that they be changed. Your refusal to permit this is an injustice to him. Wikipipedia needs to correct this officially. I far as I can see Wikipedia policy has been officially used to abuse and insult Mr Tombe and that injustice needs to be corrected. Your failure to produce the required proof is a disgrace. 72.84.68.195 ( talk) 13:38, 8 May 2008 (UTC)
FyzixFighter, I don't think that Goldstein will overtly recognize centrifugal force either. It will adopt the same attitude as your book and work on the premises that gravity is the only force involved. But when the chips are down and the orbital equation appears, there will be two terms acting in opposition to each other in the radial direction. There will be a gravity term acting radially inwards and a term of the basic mathematical form v^2/r acting radially outwards. Whatever that v^2/r is, it is certainly not an artificial construct and it certainly doesn't arise because of any human desires as your book seems to suggest. It works in tandem (opposition) with gravity to produce conic section orbits.
A high quality textbook will generally remain silent on the issue of what this term actually is. It will be quietly borrowed from that general acceleration equation that we have been looking at. And as you must surely be aware, that general acceleration equation merely exposes inertia in the Cartesian frame to be the centrifugal force and the Coriolis force in a polar frame.
Yes, you are correct in that no modern textbook is likely to overtly declare the centrifugal term to be real. In fact, your book's declaration that it is artificial should surely alarm you. To claim such with regards to that scenario is the height of delusion.
Now I'd like to draw your attention to this line in your reference,
In order to reconcile this observation with the requirement that the net radial force vanish-that is, that the circular orbit be maintained
Now consider the artificial circular motion which is associated with viewing a stationary object from a rotating frame. How does it reconcile with this requirement? According to the 'Fictitious party' there is a radially outward centrifugal force and a radially inward Coriolis force that is twice as large. Yet if we are to have a circular orbit the centripetal force and the centrifugal force must be balanced.
The reality is that the equations for the coordinate frame transformation are only designed to cater for co-rotating objects. This condition is totally satisfied in meteorology.
Can you show me an explicit citation stating that these equations apply to objects that are stationary in the inertial frame. I wouldn't be entirely surprised if you could. But nevertheless, I would like to see it explicitly stated in a book. I have a feeling that the restriction to co-rotation has been overlooked by many people who have been introduced to these equations, and the error has been passed on from textbook writer to textbook writer.
Or perhaps the error isn't even in the textbooks and the mistake lies entirely with the readers. That's why I'd like you to find an explicit reference which overtly states that these equations apply to objects that are at rest in the inertial frame. David Tombe 119.42.65.152 ( talk) 16:11, 8 May 2008 (UTC)
Nobody ever mentions frames of reference when they describe the effects that take place due to centrifugal force inside a swerving car. They talk about these events as they stand in their kitchen, which is an inertial frame, and they state that as the car swerved around the corner, they got flung to the side door.
It is a matter of opinion which I don't subcribe to, to state that these events are more conveniently described from a rotating frame of reference. No such frame is needed in the description. When have you ever heard anybody going to the bother of explaining that as they viewed things from within the car, they were accelerated twoards the side door. The man standing watching it from the street saw exactly the same thing.
Such an argument however does not necessarily extent to the Coriolis force in relation to meteorology. 119.42.69.123 ( talk) 16:16, 7 May 2008 (UTC)
Wolfkeeper, the man in the street is quite capable of observing a radial acceleration towards the side door. We don't need to consider a rotating frame of reference to observe this. David Tombe ( talk) 06:23, 8 May 2008 (UTC)
Wolfkeeper, the man in the street sees the man inside the car getting flung to the side door. David Tombe ( talk) 09:55, 8 May 2008 (UTC)
Wolfkeeper, the man in the car is co-rotating. The back of his seat pushes him tangentially. This induces a vXω force radially. If he wasn't co-rotating with the car, he wouldn't be in the car, and he wouldn't be experiencing any outward tangential force.
And yes, this radially outward acceleration translates into straight line motion in the Cartesian frame. Centrifugal force in the polar frame is the same thing as inertia in the Cartesian frame.
Look at the conversion equation. Then remove the tangential components because of Kepler's law of areal velocity. Centrifugal force stands out as an inbuilt feature of straight line motion. David Tombe 119.42.65.152 ( talk) 16:32, 8 May 2008 (UTC)
Hi everyone. I understand that there are already textbook references that support the current version of the article straight down the line. However, it would be helpful if users would add in-line citations to sections that are being "warred" over. Talk page discussion is not settling this "argument"; I think administrative action will, but the case for administrative action is far stronger if directly-cited statements are being removed. I am willing to use my knowledge of physics to evaluate whether a source actually supports a statement, but not to treat a statement as cited just because I personally know it's correct and that it could be. So if instead of just reverting, you would consider in-line citations for the statements you re-add, it would save us all time in the end! -- SCZenz ( talk) 07:30, 8 May 2008 (UTC)
I notice that Timothy Rias has responded to this message by filling up the introduction with references for matters which are not in dispute. That is a bad sign. It shows that he has lost sight of the higher picture. David Tombe ( talk) 10:32, 8 May 2008 (UTC)
In reply to the above statement. I can provide just as many textbook references that contradict what is stated in the main article. Therefore I must conclude, that since I have just as many references that contradict what you say, then what you say is not justified by your selection of certain references that agree with what you beleive. That is not science. So you need to prove what you say is true, and you have not done it. 72.84.68.195 ( talk) 14:25, 8 May 2008 (UTC)
Wolfkeeper, I am fully aware of the fact that the Coriolis force doesn't involve any change in kinetic energy. But the Coriolis force does not occur in a zero curl field. There is no vorticity in the gravitational field that could invoke the Coriolis force. Kepler's law of areal velocity eliminates the Coriolis force from gravitational problems.
There is however Coriolis force in hydrodynamics because there can be vorticity. The ω is to all intents and purposes the vorticity. David Tombe ( talk) 10:24, 8 May 2008 (UTC)
Whether or not the curl of vXω is equal to zero is irrelevant. Kepler's laws eliminate the Coriolis force from all planetary orbital theory. 119.42.68.141 ( talk) 10:11, 9 May 2008 (UTC)
I have just blocked David for 31 hours for reinsertion of the same unreferenced assertions as before (see this diff), in spite of extensive warnings regarding the need to adhere to Wikipedia's polices. David, you are welcome to edit again when the block expires, but please try to edit according the WP:V and WP:NOR policies; that is to say, please provide verifiable cites to third-party reliable sources that back up your assertions. -- The Anome ( talk) 11:00, 8 May 2008 (UTC)
Sir, Again you have created an injustice with respect to Mr Tombe. As stated above, what you state in the main article is false, and Mr Tombe has every right to dispute it. Your policy is a disgrace as I stated above. You need to correct your behavior in this matter. Mr Tombe has clearly stated his sources on this talk page and you have none to prove him wrong. You need to produce the proof and you have not produced it. 72.84.68.195 ( talk) 13:54, 8 May 2008 (UTC)
The article cites five independent sources for the consensus content:
URLs and page references are provided in the article itself.
I'm sure the credentials of Stephen T. Thornton & Jerry B. Marion can be tracked down with similar ease, but I don't have the time to do so right now.
In each case, each work has a publisher that is independent of its author. The combination of all of these sources more than suffices to comply with the Wikipedia:Verifiability policy, as well as WP:NOR and WP:NPOV, which is all that is required here.
-- The Anome ( talk) 22:58, 8 May 2008 (UTC) [updated with more details 23:45, 8 May 2008 (UTC)]
Perhaps the discussion at Taylor, p. 358, which seems to cover many of the points raised, and can be viewed at Google books, would help to settle the disputes. Brews ohare ( talk) 19:56, 8 May 2008 (UTC)
There are clearly at least three interpretations of the term "Centrifugal force"
I think most people here will agree that the most common interpretation of the term "Centrifugal force" is the pseudo force. The question is, how important are the other two interpretations? I'm beginning to think that maybe giving the second one its own article is undue weight when in fact it is just a small minority that uses it in that precise sense. Note that the second interpretation is a subset of the third, so in most cases you can't tell from a quote that it only implies the second meaning and not the third. There are some cases where it would clearly be strange to use the term as in the second interpretation. For example, consider a binary star. For star A, the gravity from star B provides a centripetal force. Consequently, the gravitational pull on star B from star A would be the "reactive centrifugal force" even though it is not acting away from the center of rotation.
My conclusion is that both interpretations 2 and 3 are significant enough to warrant inclusion in this article, perhaps in an "etymology" section, but neither is important enough to have its own article. -- PeR ( talk) 21:00, 8 May 2008 (UTC)
I've just been scouting around for some more citable references.
Here's a peer-reviewed paper that describes centrifugal force as fictitious, for those that insist that only peer-reviewed sources are valid: Merab Gogberashvili, Coriolis Force and Sagnac Effect, Found.Phys.Lett. 15 (2002) 487-493. Quote: "In the rotating frame two fictitious gravity-like forces appear, namely the centrifugal and Coriolis forces. This is an illustration of the equivalence principle, which asserts that gravity and the accelerated motion are locally indistinguishable."
And for those who like citation by independent third-party reviews of the field, and/or appeals to authority: Richard Feynman, quoted in The Natural Philosophy of Leibniz by Kathleen Okruhlik, James Robert Brown (Springer, 1985, ISBN 9027721459, page 138) as saying (referring to rotation and centrifugal force) "These forces are due merely to the fact that the observer does not have Newton's coordinate system, which is the simplest coordinate system." -- The Anome ( talk) 00:40, 9 May 2008 (UTC)
Anome has totally misrepresented what the edit war is about. He has presented this war as being over the issue of whether or not centrifugal force is real.
The war is not about whether or not centrifugal force is real, although that did become a side issue when Anome opened up a special section entitled 'Is the centrifugal force real?'.
The war is not about whether the term fictitious force is applied to centrifugal force in the textbooks. We all know that it is.
The war is about the fact that all attempts to mention the cause of centrifugal force get instantly erased from the article. That cause is rotation. And we don't need any citations to back up that assertion because it is a well known and undisputed fact. 58.147.58.54 ( talk) 06:19, 9 May 2008 (UTC)
129.194.8.73, Does a centrifuge work if it is not rotating? 119.42.68.141 ( talk) 10:05, 9 May 2008 (UTC)
Anome, absolute nonsense. I'll ask you one single question,
Does a centrifuge work if it is not rotating?
The answer is 'no'.
Nowhere in the whole article does it say that the real effects of centrifugal force arise due to actual rotation. I tried to insert it yesterday and you blocked me and reverted the clause.
That was a very bad management decision and it was done on a false pretext. It had got absoloutely nothing to do with references, and besides that, I did give a reference to the wikipedia page on the Bucket argument which illustrated the point that co-rotation situations give actual effects whereas observing a stationary object from a rotating frame yields no effects.
You are pandering to a group such as the anonymous 129.194.8.73 above who are clearly not living in the real world. His mind is focused entirely on how a stationary object appears from a rotating frame of reference. And he deduces from that, that because the effect is artificial, that then it must be artificial for all cases including the centrifuge.
And you know that the effect is not artificial in a centrifuge. And you know that the centrifuge effect only occurs when the centrifuge is rotating.
So you blocked me on totally false grounds. It had got nothing to do with citations. The wikipedia rules clearly state that no citations are needed for obvious facts. And it is obvious that a centrifuge only works when it is rotating.
As for PeR's whinning about me evading the block, I never went unto the main article. How am I supposed to answer a hail of questions coming at me on the talk pages if I'm blocked from editing? PeR is actually the root cause of this entire problem because he is the arch-fictitiousist who is desperate to conceal the cause and effect aspect of centrifugal force. David Tombe 119.42.68.141 ( talk) 12:17, 9 May 2008 (UTC)
David: Everybody will agree that the centrifuge has to rotate. But the point is "How do you describe what is happening?" You have two choices to describe the rotating centrifuge: 1) Sit in the lab frame: the stuff in the test tube tries to stay still while the tube rotates. Relative to the moving tube, the stuff moves. 2) Sit on the centrifuge: the tube isn't moving, but the mysterious fictitious forces push the stuff down the tube. Brews ohare ( talk) 13:34, 9 May 2008 (UTC)
Brews, et al: I think it's become clear that it's a waste of time trying to explain the subject to David (unfortunate as that is). I've given up trying. On the positive side, all this has resulted in a lot of group effort to make the articles clearer and better referenced. Silver lining, eh ? Plvekamp ( talk) 13:45, 9 May 2008 (UTC)
"A centrifuge is a device consisting of a rotating container in which substances with different densities are separated by centrifugal forces on the substances." "This force is opposed by the frictional force of the fluid on the particle." Page 123 The Encyclopedia Of Physics, R. M. Besancon. This source says basically what Mr Tombe has been saying in his edits which you removed and eventually blocked. Since there is now a valid citation supporting Mr Tombe's claims, you need to remove your blocks and apologise to Mr Tombe. 72.64.55.233 ( talk) 13:50, 9 May 2008 (UTC)
In the section "is centrifugal force real" the following appears
Despite the name, fictitious forces are experienced as very real by anyone whose immediate environment is a non-inertial frame. Even for observers in an inertial frame, fictitious forces provide a natural way to discuss dynamics within rotating environments such as planets, centrifuges, carousels, turning cars, and spinning buckets.
To this sentence I propose adding:
For example, a description of the centrifuge from this viewpoint is: "A centrifuge is a device consisting of a rotating container in which substances with different densities are separated by centrifugal forces on the substances.…This force is opposed by the frictional force of the fluid on the particle." [1] See, for example, the article Lamm equation.
Any objections or modifications to this addition? Brews ohare ( talk) 15:16, 9 May 2008 (UTC) I implemented this change. Brews ohare ( talk) 19:44, 9 May 2008 (UTC)
All this rotation business makes things unnecessarily complicated when one wants to understand why the rotating bucket has hydrostatic pressure that the non-rotating bucket doesn't. There is an equivalent, much simpler experiment that only requires one to think in one dimension. Imagine that you have a friend sitting with his bucket of water in his spaceship, which is "standing still" (in an inertial frame of reference). You are in your own spaceship, with your own bucket, and your spaceship is accelerating away from your friend's. From your ship's frame of reference, you don't seem to be moving, yet your friend seems to be accelerating away from you. You explain his acceleration by means of a fictitious force that acts on your friend's spaceship. This fictitious force only exists in your frame of reference. Yet, your bucket will have weight, pressure and all that, while your friend's bucket will be floating freely inside his ship. This just goes to show the difference between inertial and non-inertial frames of reference, and that real forces (of the sort that make your bucket have weight and hydrostatic pressure) only relate to acceleration with respect to the inertial frame.
I have to agree with the majority that centrifugal force is a fictitious force and that the hydrostatic pressure in the rotating bucket is due to inertia (or acceleration with respect to an inertial frame of reference), same as the hydrostatic pressure in the bucket inside the accelerating spaceship. Didn't Einstein say that force due to acceleration was indistinguishable from gravity, by the way? -- Itub ( talk) 15:52, 9 May 2008 (UTC)
Sir you must surely be as confused as those with whom you profess to be in agreement. It seems all of you have become deranged. In your thought experiment, which is basically just a fictitious situation which does not really exist and can not exist, you suppose that because your spaceship is accelerating, but you dont know that fact, that it is reasonable for you to suppose that there is some fictitious force acting to explain that the other spaceship is accelerating. That is certainly a curious state of affairs. What your fictitious example shows is that if you are ignorant of your physical state you are certainly entitled to make false conclusions regarding the actual state of affairs about which you are ignorant. But of course, your reasonable false conclusion results from the fact that you don't have accurate knowledge of your physical state. Hence the hypothesis of a fictitious force arises from ignorance of the actual state of affairs and not from any valid concept of physics. 71.251.176.68 ( talk) 20:36, 10 May 2008 (UTC)
Can an example be provided to show what this statement means? For example, a book on a table exerts a gravitational force on the table that certainly results in a Newton's third law reaction by the table. This statement either should be supported by a clarifying example, or removed. What does it mean? In this connection, notice that the centrifugal force often is referred to as "artificial gravity" e.g. for astronaut training. See also Taylor. Likewise the statement that "they cannot be felt by a person subject to them" seems far-fetched. See also the point of view in Sedimentation. Brews ohare ( talk) 19:20, 9 May 2008 (UTC)
I think one way to resolve the difficulties regarding whether the rotating frame is 'fictitious' or not, is to use the equivalence principal - i.e., the physical phenomena are the same regardless of the coordinate system used. Any reference frame is as good as another; but the coordinates you use will depend on the choice. The simplest is an inertial, Cartesian reference frame in which straight-line uniform motion (no force) involves no 'fictitious' forces. Any other reference frame (accelerating, rotating, even polar) will include 'fictitious' terms due solely to a change of coordinates.
Another way to resolve it is to use coordinate-free vector notation, but to do any practical work we need to introduce coordinates.
There's a slightly subtle point about polar coordinates - Even in an inertial frame, motion will involve 'fictitious' terms due to coordinate transformation. Try describing straight line force-free motion in polar coordinates, you'll see what I'm talking about. Some of the arguments about inertial frames miss that point. Since we nearly always analyze orbital mechanics using polar coordinates, centrifugal and coriolis terms arise. One of David's examples above included the centrifugal term in orbital mechanics and he tried to say the force was 'real.' Nobody called him on it, and I think perhaps it was because we're so stuck on rotating frames in this article that the point was missed. Plvekamp ( talk) 15:14, 10 May 2008 (UTC)
Mr Plvekamp, it apears you are confused. Feynman clearly states that it does matter which coordinate system that you use. He states that the pseudo forces "are due merely to the fact that the observer does not have Newton's coordinate syatem, which is the simplest coordinate system." page 12-11, Vol 1 of his Lectures. Your statement that one reference frame is as good as another evidently indicates you dont understand this topic. I suggest that you do go back and check up on your memory and stop pulling facts out of the air. 71.251.176.68 ( talk) 20:07, 10 May 2008 (UTC)
I'm not disagreeing with Feynman; on the contrary, I completely agree that the appearance of pseudoforces depends completely on the coordinate system. What I'm trying to say is that a rotating frame is not the only way you'll see them; you'll also see them if you use polar coordinates in a stationary frame - check the reference I linked to [6]. I provided it to show that I'm not "pulling facts out of the air." The introduction as it stands seems to concentrate solely on rotating frames.
My statement that one reference frame is as good as another was in reference to the Equivalence Principle. In other words, a change in coordinate systems does not change physical law. You may have misunderstood me, in which case I apologize for not explaining myself well.
In any case, I won't make any changes to the article unless there is consensus (unlike another recently). Plvekamp ( talk) 20:52, 10 May 2008 (UTC)
Brews, There are a number of points to clear up.
(1) The edit war has been principally about the fact that these people here have been trying to deny that a centrifuge works BECAUSE it is rotating. They have been arguing that centrifugal force occurs when we view something from a rotating frame of reference. The two concepts are quite diffent.
I have been trying to insert the cause and effect aspect into the main article, but it gets deleted instantly every time.
These people think that a rotating centrifuge is equivalent to observing a stationary centrifuge from a rotating frame whose axis is on the axis of the centrifuge.
Clearly you can see that this is nonsense. A centrifuge will not be made to work in that manner. There is no equivalence principle involved in all of this.
However, there is a group here that are trying to promote the equivalence principle, and they are quite wrong. They are denying the age old Bucket argument.
(2) Orbital theory. Polar coordinates show up both the centrifugal force and the Coriolis force. However, Kepler's law of areal velocity eliminates the Coriolis force term. No Coriolis force is involved in the gravitational field.
We are then left with a radially inward gravity force and a radially outward centrifugal force which is absolutely real.
(3)Action - Reaction. In the real scenario, when actual rotation occurs, we get a radial centrifugal force, which as regards the issue of action-reaction, behaves exactly like gravity. However in the purely fictitious situation in which we observe a stationary object from a rotating frame, any effects are only fictitious and Newton's third law will be totally irrelevant. The group that are controlling this article are focused exclusively on the latter scenario. David Tombe ( talk) 04:13, 11 May 2008 (UTC)
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Brews ohare (
talk) 14:26, 11 May 2008 (UTC)Brews, I can assure you that it is not centripetal force. I have worked at great length with that derivation and done many calculations in orbital theory. The terms in that equation are centrifugal force, Coriolis force, and Euler force. That equation in its own right doesn't infer any kind of motion. However when we apply Kepler's law of areal velocity to the gravitational field, the two tangential terms vanish. That leaves us with the radial terms. The radial terms, in the absence of gravity expose the fact that inertia is centrifugal force.
Brews, the maths in both of those articles is perfectly correct and I am well familiar with it. In fact it is basically the same maths in both cases. But you must never lose sight of the physical meaning behind the maths symbols. Those equations tell us alot. But they don't tell us everything. We need to model a real physical situation before we can decide how those terms fit in, and what they mean in any given context.
I took the gravity orbit as being the most well known physical context in which those equations are applied. Kepler's law of areal velocity is highly relevant because it gets rid of the two tangential terms. We are then left with a gravity force radially inwards and a centrifugal force radially outwards.
You have been trying to read a physical meaning into those equations in their own right. In their own right, all they do is convert polar coordinates to Cartesian. Centripetal force is not determined by those equations alone. We need to know the physical model before we can apply them and obtain a differential equation to solve.
Interestingly, they do tell us some information in their own right. If there was no applied centripetal force such as gravity or tension T in a string, or no applied torque, then in a space vortex, we would have a curved path caused by the centrifugal force and Coriolis force. If there were no vorticity, then the Coriolis force would disappear and we would be left with a centrifugal force acting alone. This would lead to a hyperbola with infinite eccentricity, which is essentially straight line motion. David Tombe ( talk) 09:34, 12 May 2008 (UTC)
Wolfkeeper, That's what is so interesting about Kepler's law of areal velocity. It means that there is no tangential acceleration. Of course we can still have a variable angular velocity.
Supposing we were to ignore Kepler's law of areal velocity. The polar coordinate conversion equations still wouldn't point us to any particular kind of motion. They would merely facilitate with the mathematical expressions that were needed in order to set up a differential equation modelling a real physical scenario.
Such a differential equation involving real tangential forces as well as real radial forces would almost certainly be non-analytical. David Tombe ( talk) 04:59, 12 May 2008 (UTC)
Wolfkeeper, I've lost track of the point that you are trying to make. I didn't bring the subject of polar coordinates up. But whoever did was correct to do so because it is relevant to the topic. David Tombe ( talk) 09:41, 12 May 2008 (UTC)
David, I just noticed your comment:
Are you saying the equivalence principle does not apply here? Can you provide a cite supporting this assertion, or is this your own original opinion? -- The Anome ( talk) 19:53, 11 May 2008 (UTC)
No Anome, this dispute has never been about cites. It has been about you and others falsely alleging that I have been adopting a fringe and unorthodox position.
I am waiting now for you to describe that position. David Tombe ( talk) 12:10, 12 May 2008 (UTC)
It appears that a digression is taking place to orbits and Kepler's laws of planetary motion. Is there a notion that something from those articles should appear here? Brews ohare ( talk) 05:16, 12 May 2008 (UTC)
Anome, a straight line motion across your kitchen does not involve any Coriolis force. It is ruled out by Kepler's law of areal velocity.
The effect that you have just described is a tangential artifact as viewed from a rotating frame of reference. The rotating frame of reference in this case is fixed in the rotating person. That is not Coriolis force. David Tombe ( talk) 12:07, 12 May 2008 (UTC)
No Anome, the radial effect can never be an artifact of circular motion. Only the tangential effect can be an artifact of circular motion.
You missed the point entirely. Centrifugal force in a zero-curl field is the same thing as inertia. There is centrifugal force built into every straight line motion. But there is no Coriolis force because Kepler's law of areal velocity eliminates it. We need hydrodynamics to get the Coriolis force. David Tombe ( talk) 12:34, 12 May 2008 (UTC)
Those derivations are correct, but they have got absolutely nothing to do with the point in question. The article is unlikely to be improved as long as SCZenz is involved in adjudicating. 118.175.84.92 ( talk) 16:44, 13 May 2008 (UTC)
FyzixFighter, I think we may now have identified the root cause of the edit war. You have just deleted my reference to the existence of two different kinds of scenario involving rotation.
(1) There is actual rotation. (2) And there is artificial rotation as when a stationary thing is observed from a rotating frame of reference.
Now I have been accused by Anome of adopting a minority or fringe viewpoint. Let's explore that so-called minority or fringe viewpoint.
My viewpoint, for which I will obtain cites if challenged, is that a centrifuge works BECAUSE it is rotating.
However, if we were to view a stationary centrifuge from a rotating frame centred on the centrifuge axis, the centrifuge would not work.
I do not believe that the "principle of equivalence" applies to rotation.
That is my viewpoint.
Is that a minority viewpoint? Do you think differently? Would you challenge it if I were to put that viewpoint into the main article? David Tombe ( talk) 09:48, 12 May 2008 (UTC)
Anome, in that case, if nobody is denying it, can you please tell me exactly what the edit war is about. And can you tell me why you erased an edit which I made to that extent and then blocked me from editing for 31 hours, extended by a further 25 hours on a petty technicality. You blocked me on the false pretext that I hadn't supplied a cite. But the rules say that a cite is only necessary if the clause is challenged. And even then, the correct procedure is to insert a 'citation needed' tag.
The edit that you erased and blocked me for is contained in this exert,
the centrifugal and Coriolis forces can have real physical effects in situations where the object in question is co-rotating such as in the case of the centrifuge device. In situations in which the object in question is not co-rotating, these fictitious forces are merely artifacts of coordinate transformation. The distinction between these two aspects of fictitious forces is the subject of a long standing debate known as the Bucket argument.Classifying such forces as "fictitious" reflects the special
Can you please point out exactly what aspect of this exert is being challenged, and why I had to be blocked for over two days for having made this edit. David Tombe ( talk) 12:28, 12 May 2008 (UTC)
Anome, coordinate frames have got nothing to do with it. It is the actual rotation that induces the centrifugal force. So if there is no co-rotation of the object in question, then there is no rotation.
The centrifuge illustrates quite clearly that centrifugal force only occurs when there is actual rotation.
So as regards your question, there would be centrifugal force based on the actual rotation of the object in question irrespective of what reference frame we viewed it from. In other words, there would be a centrifugal force associated with a 1Hz actual rotation. The frame that you mention rotating at 1.00000000001 Hz would have absolutely no bearing on the matter. David Tombe ( talk) 13:15, 12 May 2008 (UTC)
Anome, the two things in question for the purposes of co-rotation are the object in question that experiences the centrifugal force and the imaginary rotating frame of reference that you consider to be so important. If they are co-rotating, then there will be centrifugal force on the object as per the maths, and in a centrifuge that will cause a real effect.
If an object is not co-rotating with an imaginary rotating frame or even a real rotating frame, then nothing will happen to it. It will experience no real centrifugal force.
Does that point of view differ from the orthodox point of view? David Tombe ( talk) 14:11, 12 May 2008 (UTC)
It can't go to mediation until we've discovered what the dispute is about. The evidence is that a team of vandals and wikistalkers have been falsely alleging that I am adopting a minority and fringe position.
We need to await a declaration of exactly what that fringe position is. David Tombe ( talk) 12:37, 12 May 2008 (UTC)
Anome, you know the answer fine well and the answer is not being challenged. Hence no cites are necessary. A centrifuge has real effects and it only works when it is rotating.
Your deletions and blockings have got nothing to do with cites.
I think you are labouring this citations issue and hiding behind bureacratic slogans. David Tombe ( talk) 14:05, 12 May 2008 (UTC)
Anome, it says in the rules that cites are necessary when something is challenged. Are you challenging the idea that the real effects of a centrifuge only occur when the centrifuge is rotating?
Because if you are, I will get you a cite. If you are not, I will go ahead and put it in again without a cite. David Tombe ( talk) 14:24, 12 May 2008 (UTC)
OK RRacecarr, what was the problem with those edits? What would it be like for birds in an atmosphere in the absence of a gravitational field? David Tombe ( talk) 14:07, 12 May 2008 (UTC)
As long as the birds maintained a tangential path, things would seem normal. But they would have a hard job maintaining a tangential path as they got closer to the centre of the cylinder. So as they flew higher, they would begin to get disorientated.
There is also the issue of the fact that as they got closer to the center, the degree of co-rotation may reduce.This would effect the centrifugal force 118.175.84.92 ( talk) 16:52, 13 May 2008 (UTC)
David, you inserted the following text without a supporting citation:
This is [a] contrary to the predictions of the classical treatment of rotational motion (which is fully cited within the article), [b] uncited. You have persistently and consistently refused to provide cites, and this is just one more example. Accordingly, I am blocking you again. -- The Anome ( talk) 14:55, 12 May 2008 (UTC)
Go on then Anome, block it permanently and get it over with. I played by the rules. You didn't. All your blocks have been totally unlawful. That statement that I made above is perfectly true and it doesn't need any citations because it is not being challenged. It doesn't even relate to the controversy in question.
And your reversion of my reference to rotation yesterday was done under the totally false pretext of something to do with distance. 61.7.167.79 ( talk) 16:08, 13 May 2008 (UTC)
SCZenz, it's a pity that you don't know anywhere near as much about physics as you do about abuse of administrative authority. As long as you are around pushing your fictitiousist views and denying the cause and effect aspect of centrifugal force, this article will remain a mess. 118.175.84.92 ( talk) 16:31, 13 May 2008 (UTC)
Let me try to state David's viewpoint in words I understand, and without digressions in six different directions.
David agrees that observation of events from a rotating frame leads to a description using fictitious forces, including centrifugal and Coriolis forces. He also agrees that in an inertial frame the same observations do not require these forces. So far, everybody is on board.
However, David has reservations. Here are some possible interpretations of David's remarks:
Here is an alternative view of David's position:
If David can draw such conclusions from the article, perhaps so can other readers. A clear statement of these confusions and their resolution should appear in the article. Brews ohare ( talk) 15:19, 12 May 2008 (UTC)
Anome, your talking total nonsense now. Show us all a citation that states that the equivalence principle applies to rotation. As for Mach's principle, that disproves your position because it highlights the reality of the need for actual rotation in order to induce centrifugal force. 118.175.84.92 ( talk) 16:19, 13 May 2008 (UTC)
David seems to use a different definition of centrifugal force from the rest of us. In the interests of helping people communicate better, I thought I would try to state clearly what I think David means. Take the example of a particle in a centrifuge: David and everyone else agree that in the coordinate frame rotating with the centrifuge, there is a centrifugal force, determined by the rotation rate and the distance from the axis, acting on the particle. Where David's definition parts from everyone else's is in reference frames other than that particular one.
David's method: pick a reference frame rotating with the particle you're interested in, and calculate the centrifugal force. Then define that to be the centrifugal force no matter what reference frame you're in. In an inertial frame, or in one rotating twice as fast as the centrifuge, David's centrifugal force remains the same. Analysis in other frames would clearly require other fictitious forces in addition to David's centrifugal force, but he would argue that analyzing in any but the most "natural" rotating frame is an "ultra mathematical game"--the centrifugal force that the particle cares about, the one that it "sees", is the one in the reference frame rotating with it.
Standard method: pick any reference frame you want, and then define the centrifugal force relative to that frame. In the frame rotating with the centrifuge, the force is the same as David's. In the inertial frame, there is no centrifugal force. The force felt by the particle is applied by the wall of the centrifuge, and it accelerates inward in response. In the frame rotating twice as fast, the centrifugal force is twice as large as David's, but (in this special case) it is perfectly cancelled by the Coriolis force, and again the observed circular motion (in the opposite direction as in the inertial frame) is due 100% to the force applied by the wall.
Ok, maybe that will help people understand where David is coming from. Now maybe I can get David to consider whether the standard method actually might make sense to use in some situations (whether or not I succeed, the article will continue to exclude David's method until some references are produced, in accordance with WP:NOR).
As long as you are dealing with a single particle in circular motion at constant speed, David's method is fine. But what if the speed changes? With David's method, that requires a change of reference frame, which may not be convenient--angular acceleration of a reference frame introduces even more fictitious forces. Even worse, what if you have a bunch of particles, all moving around with different velocities within some rotating environment? David's method requires a different reference frame for each particle, to match with its actual instantaneous angular speed about the axis. In the standard method, all the particles are treated in the same reference frame, subject to the same (position dependent) centrifugal force. Differences in the velocities of the particles do result in differences in the fictitious forces they experience, but that is described by the Coriolis force, rather than by assigning each particle its own individual centrifugal force (which wouldn't, by the way, get rid of the need for a Coriolis force). Doesn't the standard way seem easier? Rracecarr ( talk) 15:57, 12 May 2008 (UTC)
RRacecarr, Let me now reply to your above assessment of my position. Your first part is more or less correct. We are all agreed that real outward radial effects occur when something is actually undergoing curved path motion.
In that case, why all the fuss? What is the fringe viewpoint that Anome keeps alleging that I am pushing?
And why are we not allowed to have any mention of this aspect of centrifugal force put in the main article?
I have tried on many occasions to highlight the fact that a centrifuge involves real radial effects which arise exclusively because the centrifuge is rotating. But these edits get swiftly removed every time. Itub and Timothy Rias have even tried to tell us that a centrifuge doesn't need to be rotating to work.
I was blocked from editing by Anome for inserting comments to the extent that a centrifuge does need to be rotating. And if you go to the notice boards behind the scenes, you will see that there is all sorts of panic going on and discussions about possibly blocking me permanently.
On your specific question, I would agree with you that rotating frames are useful in hydrodynamics, with meteorology being a classic example.
But not for a rotating snooker table. That never happens and it wouldn't work. There is no Coriolis force acting on free trajectories. You need to have actual curl as in hydrodynamics where the many particles are actually bonded to each other by inter atomic forces that are not subject to Kepler's law of areal velocity.
Anyway, I intend to re-insert the bit about the centrifuge into the section entitled 'Is the centrifugal force real?'. If Anome, or any of his colleagues in the administration, block me permanently on that basis, then we will all know the truth.
The truth is that there has been efforts made to play down the layman's concept of centrifugal force and to play up a fictitious aspect that is associated with artificial circular motion as viewed on stationary objects from a rotating frame of reference.
Have you got any citations regarding that theory about Coriolis force acting radially on a stationary particle when it is viewed from a rotating frame? There is a whole section on it in the main article and it seems to be given a much higher priority than anything to do with actual centrifugal force. David Tombe ( talk) 03:58, 16 May 2008 (UTC)
Itub, you said above, All this rotation business makes things unnecessarily complicated when one wants to understand why the rotating bucket has hydrostatic pressure that the non-rotating bucket doesn't.
The simple fact is that the hydrostatic pressure is induced because it is rotating. If we observe a non-rotating bucket from a rotating frame of reference, we do not get any hydrostatic pressure induced.
Hence there is no equivalence in the two situations. It is like the Faraday paradox.
So there are two distinct scenarios to be analyzed separately when answering the question 'Is centrifugal force real?'
And any attempts on my part to answer that question in relation to the actual rotation scenario are instantly erased, along with blocks and threats of permanent blocking. Such edits generate no end of panic on the notice boards behind the scenes.
So there is something seriously wrong going on. Some group here are totally intolerant of references to the real effects associated with actual rotation. David Tombe ( talk) 12:57, 16 May 2008 (UTC)
Anome, will a centrifuge work if it is not rotating? It's a yes or no answer. No need for all the hokum about reference frames.
David Tombe (
talk) 13:55, 16 May 2008 (UTC)
Yes. But he then tried to qualify it with a load of irrelevant hokum about frames of reference.
A centrifuge works BECAUSE it is rotating. End of story. There is nothing more to say on the matter. But this fact is not allowed in the main article and I was blocked for trying to put it in. So somebody has been abusing their administrative authority. David Tombe ( talk) 14:39, 16 May 2008 (UTC)
I'd like to request semi-protection for this article, and preferably for the talk page also. Both seem to be under attack from a POV-pushing anonymous from different IPs. Now there's nothing wrong with pushing POV, provided they include reliable refs, but this isn't.- ( User) WolfKeeper ( Talk) 03:53, 14 May 2008 (UTC)
p.s. I removed some anonymous comments from this page, it seems that they're David Tombe, and he's currently suspended, so that's vandalism in my book.- ( User) WolfKeeper ( Talk) 03:53, 14 May 2008 (UTC)
I've semi-protected the article; Tombe evidently is on a dynamic IP. I really don't want to protect the talk page, as then legitimate IP and new users are locked out of the article completely. In my opinion, feel free to just delete IP trolling on this talk page while he's blocked. We'll see what happens when the protection expires; may have to look into a range block, though i hate that too. Let's see how it goes. -- barneca ( talk) 04:22, 14 May 2008 (UTC)
This page is for discussing the article. Although the some of the discussions with David Tombe are related to the subject, I would really appreciate it if they could be kept on his talk page. One reason is I'd like to be up to date with the general discussion on this page, and it simply takes too long to read all the debates. Another reason is that he is currently blocked, and tempting him to answer via IPs is unfair, as that could have consequences for him. (He is allowed to edit his own talk page while blocked.) -- PeR ( talk) 15:12, 14 May 2008 (UTC)
P.S. I know I haven't always kept to this myself in the past. -- PeR ( talk)
In all the presentations of the fictitious forces, the Coriolis term and the centrifugal term appear with the same sign. Yet in the example in the section entitled "Fictitious Forces" claiming that a fictitious centripetal force acts on a stationary object as viewed from a rotating frame of reference, the two terms suddenly take on opposite signs.
Could we have a citation which explicitly states that the rotating frame of reference transformation equations apply to particles which don't themselves physically connect to the ω term.
It strikes me that someone somewhere has lost the connection between the maths symbols and the physical reality to which they are supposed to relate to. David Tombe ( talk) 13:30, 16 May 2008 (UTC)
Itub, can we please have the exact quote. David Tombe ( talk) 13:51, 16 May 2008 (UTC)
In other words Itub, there is no quote that backs up your point and the citation is bogus. David Tombe ( talk) 13:59, 16 May 2008 (UTC)
Anome, Page 233 wasn't available. We need to see an exact quote which explicitly states that the transformation equations apply to particles which don't themselves physically connect to the ω term.
The examples on page 234 relate to co-rotation so it doesn't look very promising. David Tombe ( talk) 14:16, 16 May 2008 (UTC)
There is no negative sign on your centrifugal force in the section in question in the main article. And your book doesn't say that those equations apply to particles that don't have the angular velocity ω. Where did that theory about the artificial circle come from? It's not in your book. David Tombe ( talk) 14:45, 16 May 2008 (UTC)
Now you are just talking nonsense. If the particle is stationary in the inertial frame, then it relates in no way to ω. The entire derivation of those equations was based on a particle whose tangential speed is related to ω. As for the signs, you have cooked the books in the main article by making the centrifugal force have a positive sign. David Tombe ( talk) 14:49, 16 May 2008 (UTC)
Do they have a "gun-boat diplomacy policy" too, to deal with administrators who engage in debates while continually threatening to permanently block those who they disagree with? David Tombe ( talk) 17:44, 16 May 2008 (UTC)
David: The Coriolis term depends on the velocity vector, so it flips sign if the velocity flips sign. If you look at Centrifugal_force#Examples you will see that the Coriolis force is opposite to the centrifugal force if the velocity has the appropriate direction. Brews ohare ( talk) 15:12, 16 May 2008 (UTC)
FyzixFighter, that was an interesting reference and it actually was relevant unlike the one supplied by Itub. It brought attention to the point that I have been driving at.
I have noticed that you in particular have been very interested in examining these effects starting with the coordinate-less velocity vector. We are agreed that this results in a vXω acceleration at right angles to the direction of motion and it is identical in principle to the qvXB force in electromagnetism.
This fact alone should direct you to the Faraday paradox and tell you clearly that the principle of equivalence does not apply to rotation.
Anyway, the expression vXω is the parent term for both the Coriolis force and the centrifugal force. Can you now see how Maxwell derived vXB from his sea of vortices? It's centrifugal force which he believed to be real and to be the cause of magnetic repulsion.
Anyway, those diagrams on P349 that you referred to correctly show that it doesn't matter what direction v is in to get the vXω deflection.
But I can assure you that if you split vXω into two mutually perpendicular components in polar coordinates, one being the Coriolis force and the other being the centrifugal force, then the Coriolis force will be the tangential component. The two can never act along the same line.
It was an interesting reference, but I want a reference which explicitly states that the transformation equations apply to particles that are not related to the ω vector, because the derivation explicitly requires that the particle in question possesses ω as its own angular velocity. David Tombe ( talk) 15:28, 16 May 2008 (UTC)
David. can you provide a reference that states that the transformation equation applies only to co-rotating objects? Also the reference in Marion&Thornton says (literally, I'm pretty sure, I'll check when I get home.) that if you modify Newton's second law by the terms in the transformation equation, that you get the EoM for a particle as described in a rotating frame. This means any particle including those that are not co-rotating. ( TimothyRias ( talk) 15:36, 16 May 2008 (UTC))
Brews, none of your examples involved the Coriolis force. The final example did involve a tangential deflection as viewed from the rotating frame, but that is not a Coriolis force.
Take a look at these two situations.
(a) Imagine a pole sticking up from the ground. An electrically charged projectile passes it at ten yards in straight line motion in the horizontal plane.
We will have the vXω (parent force for centrifugal and Coriolis) acting on the projectile due to its inertia. If the gravitational attraction of the pole is negligible, the straight line motion follows exactly as the solution to motion in a zero-curl field. Kepler's laws get rid of the Coriolis force and we are left exclusively with centrifugal force (inertia). The solution is a hyperbola of infinite eccentricity which is a straight line.
Now consider a particle at rest. Rotate the pole and nothing will happen.
(b) Consider the pole now to be a bar magnet with the magnetic axis along the length of the pole. This puts a curl into the field.
The Lorentz force is vXω (remember, Maxwell derived the Lorentz force with B being related to angular velocity).
This time the projectile describes a curved path due to the curl in the field.
However, rotate the pole on its magnetic axis and nothing happens.
The Faraday paradox and the Bucket argument are the same thing.
In your examples there is no curl and so there is no Coriolis force.
To get Coriolis force we need hydrodynamics. Maxwell showed that the magnetic field was hydrodynamics.
In meteorology, we get Coriolis force because elements of air move relative to the larger entrained body of rotating atmosphere. Kepler's laws don't apply on the inter molecular scale and we can see that the Coriolis force is a real effect simply by observing the spiral cyclones from space. David Tombe ( talk) 17:14, 16 May 2008 (UTC)
Hi David: Well, you haven't directly answered my question about the Dropping Ball example, although your statement "In your examples there is no curl and so there is no Coriolis force." seems to mean you disagree with it. I'd like to track down how we might differ on this example – that might help me to understand your viewpoint. To reprise the article's approach, the rotating observer sees the falling ball trace out a circular path. As with any student of mechanics, he concludes a centripetal force must be at work – otherwise the ball should follow a straight line, and obviously it does not do that. That is about as far as he gets with this problem. However, if he does a bit more study, looks at balls falling at different rates and radii, he will come up with an explanation based upon the forces F = –2mΩ × v – mΩ × ( Ω × r). Call them what you will, if these forces are put into Newton's laws the correct trajectories emerge. Where would you fault this process? Brews ohare ( talk) 18:03, 16 May 2008 (UTC)
{{
cite book}}
: |page=
has extra text (
help) and Vladimir Igorevich Arnolʹd (1989).
Mathematical Methods of Classical Mechanics. Berlin: Springer. p. §27 pp. 130 ff.
ISBN
0387968903.. They also are derived at
Fictitious_force#Rotating_coordinate_systems. Can we agree that these forces apply?
Brews ohare (
talk) 19:04, 16 May 2008 (UTC)Brews, OK, we'll start with that one. I was never denying that mathematical expression. I was saying that nobody as yet has provided a citation which explicitly states that the above equation can be applied to objects that do not physically possess the angular velocity ω. The derivation of that equation begins by considering a particle which possesses that angular velocity. David Tombe ( talk) 04:31, 17 May 2008 (UTC)
To quote from the article:
To answer this question, let the coordinate axis in B be represented by unit vectors uj with j any of { 1, 2, 3 } for the three coordinate axes. Then
The interpretation of this equation is that xB is the vector displacement of the particle as expressed in terms of the coordinates in frame B at time t. From frame A the particle is located at:
In this quotation frame A is inertial and frame B is accelerating. The derivation then carefully distinguishes between the motion of the particle and the change in the coordinates and unit vectors in the accelerating frame. The result is the equation for forces that is agreed upon. The definition of ω is as below:
If the rotation of frame B is represented by a vector Ω pointed along the axis of rotation with orientation given by the right-hand rule, and with magnitude given by
then the time derivative of any of the three unit vectors describing frame B is: [1] [2]
and
These unit vectors are attached to the rotating frame, not to the object under observation.
For Huygens and Newton centrifugal force was the result of a curvilinear motion of a body; hence it was located in nature, in the object of investigation. According to a more recent formulation of classical mechanics, centrifugal force depends on the choice of how phenomena can be conveniently represented. Hence it is not located in nature, but is the result of a choice by the observer. In the first case a mathematical formulation mirrors centrifugal force; in the second it creates it.
The primary aim of this paper is to show that in the eighteenth century centrifugal force was a problematic notion in many respects. Moreover, I intend to show that current views concerning the ideas on centrifugal force expressed by Newton in the Principia mathematica are severely affected by the projection of modern methods and ideas that are found neither in the Principia nor in works contemporary with it. I hope that my analysis will stimulate a fresh reflection on Newton's mechanics and its reception.
The Relativization of Centrifugal Force Author(s): Domenico Bertoloni Meli Source: Isis, Vol. 81, No. 1, (Mar., 1990), pp. 23-43 Published by: The University of Chicago Press on behalf of The History of Science Society.
David Tombe ( talk) 17:33, 16 May 2008 (UTC)
Anome, the point remains, can you tell me exactly what is the fringe point of view that you keep accusing me of trying to push?
Here in essence, as far as I can remember, was my introduction which started the war,
When an object undergoes curved path motion, it experiences a force directed away from the center of curvature. This force is known as the Centrifugal force (from Latin centrum "center" and fugere "to flee").
Centrifugal force should not be confused with the inward acting centripetal force which causes a moving object to follow a circular path.
In the days of Newton, Bernoulli, and Maxwell, centrifugal force was considered to be a real force, but the official position nowadays is that centrifugal force is only a fictitious force which acts in rotating frames of reference.
Where is the fringe viewpoint contained within this very basic and easy to read introduction? David Tombe ( talk) 18:22, 16 May 2008 (UTC)
Anome,
Here is a quote from Bernoulli out of the ET Whittaker book on the history of aethers.
"The elasticity which the Aether appears to possess, and in virtue of which it is able to transmit vibrations, is really due to the presence of these whirlpools; for, owing to centrifugal force, each whirlpool is continually striving to dilate, and so presses against the neighbouring whirlpools."
And here is a quote from Maxwell's paper 'On Physical Lines of Force' in relation to the mutual repulsion that occurs between adjacent magnetic field lines,
"The explanation which most readily occurs to the mind is that the excess of pressure in the equatorial direction arises from the centrifugal force of vortices or eddies in the medium having their axes in directions parallel to the lines of force"
When you first denied that these quotes indicate that Maxwell and Bernoulli believed centrifugal force to be real, you lost all credibility.
A few hours ago somebody put in a bogus citation in reply to a 'citation needed' request. When pressed to give the actual quote, they began to drag their feet. In the end, we saw that there was nothing in the citation that was relevant.
When I removed the citation, I got a warning in my tray from you not to remove valid citations.
This has been your characteristic gun-boat diplomacy style all along.
You are steering this article to support a fringe viewpoint which does not appear in any textbook, and to that end, you are abuisng your administrative powers.
The fringe theory in question was probably the original research of one of these wikipedia editors.
I will remove it now. Feel free to block me permanently if you so wish, but your intervention in this debate along with the behaviour of the others has turned the whole page into a circus. David Tombe ( talk) 04:47, 17 May 2008 (UTC)
Although I personally disagree with David Tombe on the points he has raised, response to his points has led to the tightening of the arguments in the articles and the addition of two figures, one in fictitious force and one in centrifugal force and a clarification of sentences and phrasing that make both articles much clearer. In my opinion, this improvement would not have occurred without David's input. Debate is useful, despite a tendency to boil over. Brews ohare ( talk) 16:56, 18 May 2008 (UTC)
We now have a fairly good, well referenced, account of the modern treatment of the concept of centrifugal force in classical mechanics. I'm sure it can be improved in the long term from a pedagogical viewpoint, but it's an excellent start. However, I think there are several ways in which this article could be improved further.
Firstly, it would be useful to have a section on the development of the concept of centrifugal force in the history and philosophy of science. For example, there appears to be some literature (see above) to suggest that the concept of centrifugal force held by Newton and Huygens differed somewhat from the modern concept.
Secondly, it would be useful to have a section on the everyday conceptualization of centrifugal force from the viewpoint of naive physics. There appears to be a fair amount of research on this, particularly from the viewpoint of research into science education, where it is a major stumbling block for students. There is also some research devoted to the concept as an example of metaphor formation in the artificial intelligence literature.
Thirdly, it would be interesting to have a section on how these problems are overcome in science education: there also appears to be some literature on this topic, including studies of the effectiveness of different approaches.
With these sections in place, based on reliable sources and cited to the same standards as the rest of the article, I think we would be in a good position to push towards featured article status.
Would anyone be interested in developing these topics further? -- The Anome ( talk) 10:35, 21 May 2008 (UTC)
One of three key objections to the extrapolation of the transformation equations to fictitious situations surrounds the issue of 'net radial force'.
These transformation equations are claimed to produce a net centripetal force on a particle that is at rest in the inertial frame but viewed from a rotating frame.
However, in circular motion, it is quite obvious that the net radial force is zero.
Consider the general equation for a central force orbit. It takes the form,
Applied Centripetal Force + Induced Centrifugal Force = Resultant Radial Force
This is the equation used for the gravity orbit.
We can also apply it to any orbital motion. Consider an object being swung around in a circle on the end of the string.
T for tension goes into the centripetal force slot. mv^2/r is the centrifugal force. The resultant radial force is zero and hence we end up with the equation,
T = mv^2/r
If we try to apply this equation to the artificial circle according to the theory being pushing by the fictitiousists, we will have a net centripetal force mv^2/r. The radial accleration is zero and so the equation will not be balanced.
SBharris and others seem to think that the net radial acceleration in circular motion is not in fact zero. They base this on the fact that the centripetal force has supplied an inward radial force which causes the particle to continually change its direction.
Of course such a force does exist and does produce that effect. But the net radial acceleration is still zero and so the only conclusion can be that there is also an outward centrifugal force. And this outward centrifugal force can be observed inducing Archimedes' principle in a centrifuge. It can be felt reacting against the centripetal force as like weight in the case of gravity. It can even be observed in straight line motion in the absence of any centripetal force. And most importantly of all it is used in the complex analysis of planetary orbital motion.
Consideration of the more general elliptical and hyperbolic situations makes centrifugal force an essential tool in the analysis. If we restrict our studies to circular motion where centripetal force, induced centrifugal force, and reactive centrifugal force are all equal then the induced centrifugal force becomes obscured.
Elliptical situations can be compared to weight variations in an accelerating elevator. The normal reaction and the weight change, but gravity doesn't. Likewise in elliptical motion, the induced centrifugal force (analgous to gravity) is not cancelled by the centripetal force (analgous to normal reaction) and hence the reactive centrifugal force (analgous to weight) is not generally equally to the induced centrifugal force. David Tombe ( talk) 07:26, 24 May 2008 (UTC)
We must distinguish between applied and induced effects. The transformation equations tell us no physics. They merely tell us the mathemtical form of a force that acts at right angles to a motion. They tell us nothing about the source of either a centrifugal force or a Coriolis force.
We need actual physical situations in which to apply these equations to.
One good example is a rotating turntable with a radial groove in which a marble can roll along freely.
This situation demonstrates induced centrifugal force as a real radial effect.
But there is no naturally occuring induced Coriolis force in curl-free space.
When the marble rolls out radially, it is constrained to a co-rotating radial path by an 'Applied Coriolis' force in the tangential direction. This applied Coriolis force is directly analgous to centripetal force.
The marble in turn will cause an equal and opposite tangential force on the turntable. This will be a "Reactive Coriolis Force" by analogy with reactive centrifugal force.
This article has totally played down "induced centrifugal force" and relegated it to "colloquial centrifugal force" and more recently to the classic newspeak terminology "Centrifugal Tendency".
Rotation as the cause of induced centrifugal force has been censored in the main article. David Tombe ( talk) 08:00, 24 May 2008 (UTC)
Brews, the point that I was making was that in the case of the marble rolling out the radial line, the Coriolis term in the above equaion applies and so does the centrifugal force term.
But the equation above doesn't tell us why they apply. We know that they apply simply by observing the scenario. We know that the centrifugal force is induced in the radial direction. We know that there is an applied and a reactive Coriolis force in the tangential direction. The equation on its own tells us absolutely nothing in the absence of a real physical scenario within which to apply it. David Tombe ( talk) 14:10, 24 May 2008 (UTC)
Brews, it's not even a transformation equation. It tells us nothing. It is modern physics gone mad. It gives us the mathematical form of the centrifugal force (and/or the centripetal force) and the Coriolis force and nothing more.
If you think that that equation contains real physics, then can you tell me exactly what trajecory it describes?
It's supposd to describe effects as viewed from a rotating frame. But it will only do that if those effects actually exist. David Tombe ( talk) 14:42, 24 May 2008 (UTC)
Brews, in the dropping ball example, all I can see is an artificial circular motion imposed upon the actual motion when it is viewed from the rotating frame.
I don't see either a centrifugal force or a Coriolis force at work. From the rotating frame of reference, we would need to see a tangential acceleration before we could start talking about Coriolis force. And we would need to see some radial acceleration before we could start talking about centrifugal force.
Those so-called transformation equations don't even describe the artificial circle.
The dropping ball is quite simply not a demonstration of either centrifugal force or Coriolis force.
I gave you the best demonstration. It is a marble rolling along a radial groove on a rotating turntable with a wall at the edge to hold it in.
That gives you everything,
(1) Induced centrifugal force
(2) Applied centripetal force
(3) Reactive centrifugal force
(4) Applied Coriolis force
(5) Reactive Coriolis force
The only thing it doesn't give you is induced Coriolis force and applied centrifugal force.
Induced Coriolis force is a tricky one, but applied centrifugal force would occur if an engine were to accelerate an object radially outwards along a groove on a rotating turntable. David Tombe ( talk) 16:38, 24 May 2008 (UTC)
No Itub, if the groove were curved, any radial force would be centripetal and centrifugal. Centrifugal force is a radial effect caused by actual tangential motion, no matter how we look at it. David Tombe ( talk) 09:56, 29 May 2008 (UTC)
In the inertial frame, the diplacement is
In the rotating frame the ball drops veritcally in the same way, but appears to rotate:
This equation is the displacement of the ball as recorded by the rotating observer in their reference system. In the rotating frame the unit vectors appear stationary, so their estimate of the acceleration is
that is, an inward centripetal force. Having no physical means of supplying this force. such as a tether or gravity, these observers resort to the fictitious forces of the article. When these fictitious forces are considered, the rotating observer agrees with the inertial observer that there is no real force on the ball, only the ubiquitous forces that they see everywhere, forces without apparent origin in gravity, electromagnetism etc.. Brews ohare ( talk) 17:21, 24 May 2008 (UTC)
David: I'll intersperse my comments among yours:
David: These remarks are incorrect. Circular motion when projected on an axis does become simple harmonic motion along the axis. That does not mean that circular motion IS simple harmonic motion. It means its PROJECTION is simple harmonic motion. Your remarks about radial acceleration have been dealt with completely and authoritatively by other commentators in earlier exchanges. Your idea here is plain and simply a misconception. Please re-read what has been said about this. For example, by SCZenz below. Brews ohare ( talk) 04:21, 27 May 2008 (UTC)
SCZenz, we are exclusively looking at the radial component of the acceleration. That is all that is involved in central force analysis. Any advanced classical mechanics textbook will confirm that fact.
The only equation which is relevant for this entire article is,
applied centripetal force + induced centrifugal force =
It is a second order differential equation and r is the variable. The centrifugal force is naturally induced by tangential motion and all we have to do is insert the applied centripetal force.
When we have circular motion, will be zero and hence the centripetal force will be cancelled by the centrifugal force.
That is all there is to it.
You can use that equation to analyze any central force situation.
But in your artificial circle example, you have a net inward centripetal force and so the equation is unbalanced. David Tombe ( talk) 07:45, 25 May 2008 (UTC)
SCZenz, have you never seen the orbital equation being solved in an applied maths textbook? That equation that I have cited is a scalar equation. We are only interested in the radial component of the acceleration and variations in the radial magnitude. David Tombe ( talk) 10:38, 26 May 2008 (UTC)
David: It is your reading of the math books that is faulty here. If you wish to challenge the orthodox treatment of the article, you'll have to get mathematical yourself. I'm of the opinion that you are completely wrong and what you claim cannot be proven. You'd be more useful as a contributor if you focussed on matters other than the rigor of the approach, which is in good shape as it is now. Brews ohare ( talk) 04:21, 27 May 2008 (UTC)
To proceed, the fictitious force is:
Vector Ω describes the rotation of the rotating frame. If they observe the ball to be moving counterclockwise, this rotation is clockwise so:
Hence, Ω × v is:
Consequently, the Coriolis force (related to -2 × the above) is inward radial with twice the value of the outward radial centrifugal force, leading to the rotating observer's requirement of an inward centripetal force, as calculated above. Brews ohare ( talk) 17:59, 24 May 2008 (UTC)
Hi David: I'll intersperse comments between yours:
I do not understand how the derivation is so restricted. Please spell out the mathematical assumptions that are the supposed source of such restriction. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
This is simply an assertion on your part with no support. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
Again, I fail to see any such restriction in the mathematics. Please point out mathematically where your viewpoint comes from. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
This notion is your own, and has no basis. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
Brews, it's not my own notion. In a gravity orbit, when there is circular motion, the radial acceleration absolutely has to be zero. See the new section below. David Tombe ( talk) 07:15, 27 May 2008 (UTC)
David: two problems as I see it. Problem 1 is that you are so far off the beam that it may well be impossible for you to understand the presented arguments at all. Problem 2 is that you are unwilling to adopt the perspective of the article and show how it runs amok. Instead you flail away at it from premises that are of your own invention, thereby completely disconnecting yourself from any viable conversation. I have taken the time to outline in mathematical detail the approach of the article (which is also the approach of all published articles on the subject that I have read to date, and certainly that of the most reputable ones). In contrast, you have not undertaken to go through this math and point out what you consider to be its deficiencies. I find that reluctance on your part to be a failure to engage in responsible argument. If you were to do that, I believe you would rapidly identify your mathematical errors and abandon your viewpoint. Brews ohare ( talk) 04:28, 27 May 2008 (UTC)
SBharris, the derivation of the transformation equations is essentially the same maths that is involved in polar coordinates. All we are doing is obtaining mathematical expressions in the radial and tangential directions for a force that acts at right angles to a motion.
The Coriolis force term is unequivocally a tangential term.
Whoever was first to apply that Coriolis term to radial motion made a big mistake and it doesn't surprise me at all if Feynman fell for it too, or for all I know maybe even originated it.
On radial motion there is only one important equation. It is,
Applied centripetal force + induced centrifugal force =
Hence if we have a circular motion, then will necessarily be zero and the centrifugal force will be exactly balancing the centripetal force.
It has got nothing to to with frames of reference. We can see radial motion in a system perfectly well without having to rotate with that system.
Your big problem is that just because you have seen that a centripetal force is acting radially inwards, you then assume that there must be a net radially inward acceleration. Yet it is obvious that there isn't.
So you look at = zero yet still claim that there is a net radial acceleration. This is because you don't want to involve the centrifugal force which is a critical aspect of the entire central force analysis.
And now having realized that since gravity and centrifugal force are both radial and that hence if one is real, the other must also be real, you have decided to opt for the ludicrous conclusion that they are both fictitious. David Tombe ( talk) 08:21, 25 May 2008 (UTC)
The orbital equation,
Applied centripetal force + induced centrifugal force =
is a scalar equation. The only variable is the radial distance. It is solved as a scalar equation in standard university applied maths textbooks such as Goldstein's.
If you would only apply that equation to any non-circular scenario, then all your problems regarding centripetal force, reactive centrifugal force and induced centrifugal force would be explained. But by confining your studies to circular motion, the ensuing equality of the three blurs the distinction between them.
On another matter, there are only two directions in space. There is radial and tangential. That is clear on both the microscopic and the cosmological scales. Cartesian coordinates and Newton's law of inertia are only good in the limited close-up context as like inside a cuboid kitchen where hyperbolic motion appears like straight line motion.
And because of Kepler's law of areal velocity, there is no naturally occuring Coriolis force and we don't need to do a full vector analysis of the problem.
And it's a pity that Itub doesn't pay as much attention to what Maxwell says as he does to what Feynman says. Feynman contributed nothing towards either classical mechanics or classical electromagnetism. You'll have to learn to move out of that 'Feynman worship' attitude whereby scientific progress ends forever at the mistakes that Feynman didn't spot. David Tombe ( talk) 10:08, 26 May 2008 (UTC)
I've now started a section on the historical development of the modern conception of centrifugal force in this article. I am by no means an expert in the history of science, and I'm unsure about how the references I've cited hold together: could an expert please review the material I have added so far? There appears to be significant work on this topic by Domenico Bertoloni Meli (for example, [12], [13]), however, most of the interesting papers on this subject are behind a paywall and inaccessible to me. -- The Anome ( talk) 12:23, 25 May 2008 (UTC)
SBharris, even engineers know that a component of a vector is a scalar, and that the central force equation is a scalar equation in radial distance. Are you denying this scalar equation which is in all texbooks about orbital theory,
Applied centripetal force + induced centrifugal force =
We are only concerned with the radial direction. You have consistently reminded us all that the centripetal force acts radially inwards and that it changes the direction of the particle even when the tangential speed remains constant. You seem to think that you are educating people that don't know the difference between speed and velocity.
But you are the one who has failed to tell us all why it follows that, if there is an inward radial centripetal acceleraion, that there must be a NET inward radial acceleration. In circular motion, there clearly isn't a net inward radial acceleration because has to be zero.
Are you denying the above equation? David Tombe ( talk) 06:25, 27 May 2008 (UTC)
SBharris, that is the exact equation which is used in advanced classical mechanics textbooks. It is a scalar equation and the variable is the radial distance. There is no tangential acceleration involved in any of the problems that we have been discussing. In a circular orbit, we have an inward radial centripetal force balanced by an outward radial centrifugal force and hence will be zero.
It is now clear that you are stuck in the limited high school mode where they emphasized only a part of the overall picture. They emphasized the fact that velocity has both magnitude and direction and that a centripetal force changes the direction of the particle while leaving the speed unchanged (in cases of uniform circular motion).
You have not moved on from that. I have taught that myself. But I am showing you the equation that is used in planetary orbital theory. It is in the advanced textbooks and you are simply denying it. It shows clearly that must be zero in a circular orbit. However in your artifact circle, this equation is not balanced because the application of the transformation equations to that scenario is a nonsense. David Tombe ( talk) 10:50, 27 May 2008 (UTC)
Wolfkeeper, You said above that,
I got two self-evident accelerations, a radial one outwards and the coriolis that always curved the velocity in the opposite direction to the frame rotation.
The centrifugal force will have been real and dependent on the exact angular velocity of the particle in question.
Regarding your observed Coriolis artifact, did it ever act in any direction other than the tangential direction? David Tombe ( talk) 10:16, 26 May 2008 (UTC)
Wolfkeeper, a purely tangential motion will never go inside the circle. If you see anything going inside the circle, it means that there was a radial motion to begin with.
Once again, you are too focused on artifacts to actually see what centrifugal force really is. David Tombe ( talk) 06:58, 27 May 2008 (UTC)
Wolfkeeper, well at least you are now admitting that the centrifugal force only acts on co-rotating objects (although it's not quite as simple as that). The Coriolis force on a roundabout will be an applied force which acts tangentially on co-rotating radial motion and it is likely to trip a walker up if he decides to walk a radial line on a roundabout.
No tangential motion on the roundabout can possibly cause a deflection to act such as to move the object inside the circle of which it forms a tangent. David Tombe ( talk) 11:10, 27 May 2008 (UTC)
We need to get to the point here. Is everybody denying this scalar equation,
Applied centripetal force + induced centrifugal force =
It's a second order differential equation in radial distance and it is used to solve planetary orbital problems. It can also be used for any central force scenario.
Are you all denying this equation? It is found in any advanced classical mechanics textbook.
It contains one out of at least four reasons why the artificial circle idea is nonsense.
I have been accused of not having pointed out the maths errors in the transformation equations despite having done so on numerous occasions. The equation above relates to a very important one of those maths errors.
So do you all accept this equation or not? David Tombe ( talk) 06:54, 27 May 2008 (UTC)
TstoneT, I'm not sure what you mean about stationary polar coordinates. Does that mean no tangential motion? We need the tangential motion to induce radially outward centrifugal force. Stationary polar coordinates would only be useful if we were focusing exclusively on gravity problems where things fell straight downwards. David Tombe ( talk) 07:23, 29 May 2008 (UTC)
Itub, in your artificial circle example, you also use the radial direction and that's what we're comparing it with. No need to play the old trick of hiding behind Cartesian coordinates.
Your so called centripetal force that derives from the Coriolis force is in the radial direction. At least that is what you have been trying to argue, so you can't have it both ways. In your artificial circle example you have a net inward radial force. That is impossible in circular motion. In circular motion is zero because the centrifugal force balances the centripetal force in the radial direction. Your artificial circle example causes a total imbalance in the central force orbit equation. David Tombe ( talk) 10:58, 27 May 2008 (UTC)
No Itub, the entire transformation theory which you are basing it all on is done in polar coordinates and your Coriolis force supposedly swings into the radial direction. You have a net radial force for a circular motion and so your theory is a nonsense.
You cannot keep jumping out of polar coordinates when it suits you. David Tombe ( talk) 11:19, 27 May 2008 (UTC)
Example: | Inertial frame viewpoint | Rotating frame viewpoint |
---|---|---|
"Real rotation" |
|
|
"Artificial circle" |
|
|
Anome, it doesn't at all surprise me that you agree with Itub. But your boxes above completely ignore the fact that if centrifugal force and centripetal force both act in the radial direction, then we either have them both or we have neither. In your first box you acknowledge radially inward centripetal force while denying radial outward centrifugal force even though we know that in circular motion, must be zero.
And it is that latter fact which is the key point in the dispute. Your boxes are just sheer obfuscation. In the artificial circle, the radial length remains constant, hence must equal zero. But in your theory, you are ascribing to it a net inward radial force.
On the issue of consistency, I am the one that has been totally consistent. I talk only about the radial dircection. You are the ones that keep jumping between Cartesian and polar coordinates like stage magicians, and switching off centrifugal force when you think that nobody has noticed. David Tombe ( talk) 03:04, 28 May 2008 (UTC)
FyzixFighter, you are telling me something that I already know. I know all about polar coordinates and their derivation. But when we get to central force problems, it all reduces to a scalar equation in the radial length.
is to all intents and purposes the radial acceleration in the context. If you don't want to call it that, then so be it. But the physical realities will not change.
The term has to be zero for a circular motion. Hence, the artificial circle example fails because it talks about a net centripetal acceleration in the radial direction. In a proper circular motion, the centrifugal force and the centripetal force will cancel and will be zero. David Tombe ( talk) 07:12, 29 May 2008 (UTC)
Here's a quote from the wikipedia verifiability policy,
Editors should provide a reliable source for quotations and for any material that is challenged or is likely to be challenged, or the material may be removed.
Let's see if the administrators abide by the rules or not. I have added into the introduction that centrifugal force in the so-called colloquial sense (not my choice of terminology) occurs in connection with rotation.
Is anybody challenging this fact? If so can they give me an example of colloquial centrifugal force that is not connected with rotation?
If my insertion is deleted, it proves that you are merely throwing pies, and that you are not in the least interested in centrifugal force. David Tombe ( talk) —Preceding comment was added at 07:23, 27 May 2008 (UTC)
No Anome, the article is about centrifugal force in physics not in politics. Are you being serious, or are you just being silly? David Tombe ( talk) 10:52, 27 May 2008 (UTC)
Well now you've got Wolfkeeper claiming that the articles are on topics and not terms. I suggest we remove the reference to political centrifugal force. David Tombe ( talk) 11:26, 27 May 2008 (UTC)
Brews, so what have you got to say about Anome's introducion of 'political centrifugal force' into the introduction? Would you delete it? David Tombe ( talk) 03:45, 28 May 2008 (UTC)
Anome, that doesn't mean that you have to remove the other part with it. You blended your political centrifugal force idea with colloquial centrifugal force as a means of being able to deny the need for rotation. Now that you realize that you can't do that, it is no excuse to remove the whole sentence. I'm going to put the original sentence back again as it was before you added the political bit. David Tombe ( talk) 05:50, 29 May 2008 (UTC)
It is saddening to see what terrible shape articles like planetary motion are in, where 1/10 the effort spent on the recalcitrant D Tombe would improve Wikipedia by several orders of magnitude. Brews ohare ( talk) 16:33, 27 May 2008 (UTC)
SBharris, the boxes above are sheer obfuscation and they totally neglect the fact that if centripetal force and centrifugal force both act radially then we can't switch one off and leave the other on.
In a circular motion, the radius remains constant. Hence the scalar quantity must be zero. We know that there is a radially inward centripetal force. But there must also be a radially outward centrifugal force. That's how the planetary orbital equation works.
Your boxes above were downright deceit to mask out the truths behind the planetary orbital equation and the fact that the artificial circle is a nonsense concept. David Tombe ( talk) 03:11, 28 May 2008 (UTC)
Hi Itub: Of course you are right, and David has been told this several times already with no apparent result. Brews ohare ( talk) 14:16, 28 May 2008 (UTC)
Itub, and how exactly do you reason that out? If the particle were moving in a straight line, it would already have an outward centrifugal force relative to the point origin in question. The centripetal force compounds with it to cancel it and cause curved path motion. When the two are exactly balanced we get circular motion and zero radial acceleration.
Can you not see that a straight line motion contains an outward centrifugal force realtive to any point that does not lie in its path? This is known as inertia. David Tombe ( talk) 05:55, 29 May 2008 (UTC)
Itub, the centrifugal force is in the radial direction. Your artificial circle uses the radial direction. You are trying far too hard to write off the centrifugal force by looking at the real example in the limited context of Newton's law of inertia. Newton's law of inertia is only god for cuboid kitchens. When we go to the cosmic scale or the microscopic scale, then the radial direction is the only direction that has any meaning. David Tombe ( talk) 09:39, 29 May 2008 (UTC)
I noticed yesterday that quite a bit of deceit went on. I added a clause to the introduction stating that centrifugal force had to be considered in conjunction with rotation.
Anome, knowing fine well that that is a true fact, for some reason doesn't want that fact mentioned.
So in order to obfuscate it, he blended the sentence in with the totally unrelated topic of 'political centrifugal force' as a cheap way of being able to claim that centrifugal force doesn't have to be connected with rotation.
This was a very cheap and pathetic tactic and it is totally contrary to wikipedia's rules.
So in order to expose what was going on, I split the sentence into two to clarify that we were talking about two totally unrelated topics.
Wolkeeper then comes in and reverts, citing the wikipedia rules that the pages are on topics and not terms.
But if Wolfkeeper had been genuine, he would simply have removed the political reference.
Instead, in an act of wikistalking and total hypocrisy, he retained the very subject that he was objecting to.
Wolfkeeper and Anome were clearly on opposite sides of the fence on this issue, but there would be no question of Wolfkeeper wanting to demonstrate any cracks in the united front.
So Wolfkeeper actually restored Anome's edit and the reference to political centrifugal force still remains, contary to wikipedia's rules.
Wolfkeeper was made fully aware of why I then re-reverted, but he just ignored it and reverted again.
That in my opinion suggests that there is no longer a serious scientific debate going on and that it has merely degenerated into the throwing of pies.
To clear this matter up, could we have a united statement from Wolfkeeper and Anome as to whether or not the political centrifugal force references should remain in the introduction?
I would imagine that any united decision will be totally steeped in politics, and neither in science nor wikipedia rules and regulations. David Tombe ( talk) 03:26, 28 May 2008 (UTC)
I think there's a problem with this article, beginning in the first sentence, where centrifugal force is defined as follows:
"Centrifugal force is a fictitious force that is associated with the centrifugal effect, which is an apparent acceleration that appears when describing physics in a rotating reference frame; centrifugal force appears to act on anything with mass considered in such a frame."
One problem with this attempted definition is that it refers to "rotating reference frames", whereas it should really refer to non-inertial coordinate systems, which need not be rotating. (I see there has been some discussion of this point previously - "polar coordinates" - but the point doesn't seem to have been absorbed or reflected in the article.) Perhaps it would be more paletable to replace "rotating reference frame" with "rotating or curved coordinate systems". TstoneT ( talk) 18:13, 28 May 2008 (UTC)
The main problem here is that most of the editors don't want to look at elliptical, hyperbolic, or general curved path motion. They want to focus exclusively on circular motion. That has been the cause of alot of the confusion.
Centrifugal force is something that is much more general than that which is associated with rotating frames of reference.
It is best to study the phenomenon from the perspective of polar coordinates in the inertial frame and to view centrifugal force as an absolute induced radial effect, induced by tangential motion.
If we are going to insist on clouding the issue with rotating frames of reference, then it will get confusing for cases of partial co-rotation because in reality we are only interested in the actual angular velocity of any particle in question.
The planetary orbital equation is about the best and most useful demonstration of centrifugal force in its general form. But from what I can see, there is a great reluctance on the part of the editors here to face up to elliptical or hyperbolic motion. David Tombe ( talk) 06:03, 29 May 2008 (UTC)
Wolfkeeper, you are too biased and too involved in maintaining a united opposition to everything that I say, for your opinions to be worth anything. David Tombe ( talk) 09:51, 29 May 2008 (UTC)
Polar coordinates yield very useful mathematical expressions. They yield the radial and the tangential forms of acceleration when it applies at right angles to the direction of motion.
But they don't describe any particular motion. They don't tell us if the effects are applied or induced or if the radial term is a centrifugal force or a centripetal force. It is only the vector convention which causes the radial convective force to point inwards.
In order to make full use of polar coordinates, we need to use them in conjunction with a real known physical situation.
The gravity orbit is a prime case in point. We select the expressions from the polar coordinates and apply them in the direction which we know makes physical sense. The radial convective term becomes an induced outward centrifugal force and we use Newton's gravity expression for the radially inward centripetal force.
Once we have applied the polar coordinates correctly to a real physical situation, then they become an excellent tool for analysis. They become considerably superior to the limited bastardization of the exact same maths, which is known as "rotating frames of reference".
A further example of the need to introduce physical reality before applying polar coordinates is the case of Kepler's law of areal velocity. It's an observed physical law. It means that we can eliminate the tangential terms. It means that there is no naturally occuring Coriolis force in free gravitational space. David Tombe ( talk) 06:57, 29 May 2008 (UTC)
Wolfkeeper, in your docking scenario you will have to introduce another angular velocity. It will be a three body problem.
The bottom line is that the three body problem is non-analytical and we do not need to consider it in order to understand what centrifugal force is about. In practice, it will all be done numerically on the computer.
It's interesting how keen you, Anome, and Timothy Rias are to introduce the three body problem which can't be accurately analyzed, yet you are totally averse to looking at the two body problem in planetary motion.
I can only conclude that none of you can understand two body planetary orbital theory and so you all sweep it under the carpet.
You much prefer to introduce the three body problem knowing that nobody can understand it. David Tombe ( talk) 05:07, 30 May 2008 (UTC)
Centrifugal force can be understood in its most general form in conjunction with planetary orbits. The general equation for any central force motion is a scalar equation and it takes the form,
Applied centripetal force + centrifugal force = m
where r is the radial length. In the case of planetary orbits, the centripetal force is the inward acting force of gravity.
The centrifugal force and the centripetal force that act on the same body are not necessarily balanced, and they should not be considered as an action-reaction pair. When they are balanced, we will have a circular motion, but even then the centrifugal force and the centripetal force should not be considered as an action-reaction pair because this is just a particular situation.
Newton's third law of motion is satisfied across two interacting bodies. For example, in the case of the Earth and the Moon, the centripetal force (gravity) that acts on the Earth is balanced by an equal and opposite centripetal force acting on the Moon. Likewise, the outward centrifugal force acting on the Moon is balanced by an equal and opposite centrifugal force acting on the Earth.
The reaction to a centripetal force across two bodies is sometimes called a reactive centrifugal force. The centripetal force and the reactive centrifugal force are always equal and opposite and they form an action-reaction pair. The reactive centrifugal force is essentially the centripetal force from the perspective of the other body.
In the gravity orbit, in the general case when the centripetal force and the centrifugal force are not balanced, the term will be non-zero and we will have an elliptical, parabolic, or hyperbolic orbit. David Tombe ( talk) 06:35, 29 May 2008 (UTC)
PeR, it's straight out of the advanced applied maths textbooks such as Goldstein's. Have you ever studied planetary orbital theory?
The whole point of polar coordinates is to concentrate exactly on the particle under consideration which in general will have a variable angular velocity.
I see absolutely nothing argumentative about this section. Your deletion of it from the main article was just a further example of your continual efforts to deny what centrifugal force is all about.
And it's strange how you were happy enough with the other sentence until I added the clause 'in connection with rotation'. It is your denial of the connection between actual rotation and centrifugal force which is the sole cause of this edit war. And the support you are getting from the crowd and the administration is a combination of corruption, bonding, and ignorance. David Tombe ( talk) 09:31, 29 May 2008 (UTC)
A few days ago, I predicted that the reference in the introduction to colloquial centrifugal force would soon vanish once you guys realized the implications of it.
It seems that I was correct. Anome's technique was to first mix it all up with 'political centrifugal force'. That was the obfuscation stage. The next stage was to remove the whole lot on the grounds that political centrifugal force was inappropriate.
Clearly we have group corruption going on in order to present a totally false and fictitious view of what centrifugal force is about.
Any whisper of centrifugal force being a real radial effect, is swiftly erased. David Tombe ( talk) 10:02, 29 May 2008 (UTC)
Then change it back to colloquial again. David Tombe ( talk) 10:16, 29 May 2008 (UTC)
Wolfkeeper, you are a wikistalker and a hypocrite and an absuser of administrative authority.
That edit of mine was already there for a long time and it didn't worry you before. I have got absolutely no confidence regarding your knowledge about this topic.
It is clear that you are here to push one big lie. David Tombe ( talk)
Wolfkeeper, you do not have the right to restrict this article to centrifugal force solely in connection with rotating reference frames. You have already created a dog's dinner by separating reactive centrifugal force to a separate page.
This article should mention centrifugal force in it's most general sense.
But it is quite obvious to everybody that you are just a wikistalker who is ganging up with a crowd who know nothing whatsoever about planetary orbital motion.
And because you know nothing about it, then nobody's allowed to know anything about it.
You are a totally corrupt editor who is being backed up by a crowd who need to learn a bit about centrifugal force before they are in a position to edit these pages David Tombe ( talk) 10:27, 29 May 2008 (UTC)
Wolfkeeper, the paragraph covered centrifugal force and nobody had objected to it when somebody else inserted it. It was only because I re-inserted it, after Anome deleted it in conjunction with his nonsense political centrifugal force idea, that you deleted it.
I get warnings in my tray not to accuse people of wikistalking even though it's quite permissible to go to the administrator's noticeboard and file a complaint of wikistalking.
You lot have broken the rules so many times that you can't be taken seriously.
You are a wikistalker if ever there was a wikistalker. And so is PeR. You are both top grade wikistalkers. And so are Anome and SCZenz.
Now if you don't like being exposed to the truth, then go ahead and do the honours, but I can assure you that you are a wikistalker.
It wouldn't matter what I put in the main article, whether it was sourced or not. You would routinely come along and delete it on the basis of a lie in the full knowledge that you are being supported by a crowd. You have a chip on your shoulder because you have been pushing a nonsense theory that has been exposed. David Tombe ( talk) 06:19, 30 May 2008 (UTC)
So what is the scope of this article? My intention was that it should only include D'Alembert forces as with this NASA page for example, but there's a <cough>persistent</cough> minority that want to include polar coordinate 'centrifugal forces' as well. I'm of the opinion that they're somewhat different, and certainly the associated coriolis terms are rather different. I think that if we integrate them the connectivity to other articles becomes problematic.- ( User) WolfKeeper ( Talk) 10:29, 29 May 2008 (UTC)
Anome, you must be joking. Analyzing two body planetary orbital theory is much easier in polar coordinates that it is in Cartesian coordinates. David Tombe ( talk) 05:10, 30 May 2008 (UTC)
A generalization of centrifugal force beyond a rotating frame would be to a frame in complicated motion. The general case is covered by this equation from fictitious force:
The article on centrifugal force treats the case of a fixed direction for the axis of rotation of the frame. A more general case would allow the frame Ω to vary in time both in direction and magnitude. If the observer moves in an elliptical or hyperbolic trajectory, the acceleration of the origin becomes a factor, as well as the rotational terms. The fictitious forces due to acceleration of the origin of the frame are not normally considered to be centrifugal or Coriolis terms.
It should be kept in mind that centrifugal force is not related to kinetics, but kinematics; therefore, introduction of mechanism is out of place, I'd say, and the role of planetary motion would be only as an example of a general approach for observational frames moving with time-dependent speed along 3-D curves with arbitrary Ω (t). So a frame fixed to the Earth has rotational aspects that include the precession of its Ω (t) (actually changing direction with time) and accelerations resulting from its elliptical rather than circular path around the Sun. The analysis of this case introduces secondary issues that possibly exceed the scope of an introductory article, and should be in another article. Brews ohare ( talk) 15:49, 29 May 2008 (UTC)
There are countless references for the fact that the radial fictitious force arising in stationary polar coordinates is called centrifugal force. Just to give two examples, with the relevant quotes:
(1) "An Introduction to the Coriolis Force" By Henry M. Stommel, Dennis W. Moore, 1989 Columbia University Press. "In this chapter we have faced the fact that there is something of a crisis in intuition that arises from the introduction of the polar coordinate system, even in a non-rotating system or reference frame. When we first use rectilinear coordinates to understand the dynamics of a particle, we commit our minds to the simple expressions x" = F_x, y" = F_y. We think of the accelerations as time rate-of change [per unit mass] of the linear momentum X' and y'. Then we express the same situation in polar coordinates that partly restore the wanted form. In the case of the radial component of the acceleration we move the r(theta')^2 term to the right hand side and call it a "centrifugal force."
(2) Statistical Mechanics By Donald Allan McQuarrie, 2000, University Science Books. "Since the force here is radial, it is convenient to use polar coordinates. Taking x = r cos(theta) and y = r sin(theta) [i.e., stationary polar coordinates] then... If we interpret the term [r(theta')^2] as a force, this is the well-known centrifugal force..."
Many more references can be provided it required. Frankly, this is not a particularly controversial point (aside from the editors of this wikipedia article, apparently). As I said before, centrifugal forces (like all inertial forces) are essentially defined as certain components that appear in the equations of motion when those equations are expressed in terms of non-inertial coordinates. In general, if we allow the coordinates to be curved in both space and time, several inertial terms appear in the equations of motion of a particle, and we call some of these terms “centrifugal”, some “Coriolis”, and some are given less familiar names, or aren’t named at all. If f is the mapping function to inertial coordinates, then all the inertial terms are of the form f_mn x^m/dt dx^n/dt with the understanding that the time coordinate is also one of the indexed “x^n” coordinates. It’s customary (and entirely reasonable) to call the diagonal terms “centrifugal” and the off-diagonal terms “Coriolis”. When you assert that stationary polar coordinates give something that looks like a centrigual force but really isn’t, you are sort of posing a zen riddle (like “Wagner’s music is better than it sounds”). It “looks” like a centrifugal force because it’s a diagonal term, it’s a fictitious force in non-inertial coordinates, and it points radially outward – all of which are essentially the definition of a centrifugal force.
PeR objected because he says the “theta dot squared” term refers to angular speed of the coordinate system in the case of centrifugal force, whereas it refers to angular speed of the particle in the case of stationary polar coordinates, so these are two different things. However, the motion of the particle and the motion of the (non-inertial) coordinates are defined relative to each other. In terms of stationary polar coordinates the value of theta is really just the angular position of the particle with respect to the coordinate system, and if that system is rotating, it simply adds to theta. In other words, if the coordinates have angular speed W and the particle has angular speed w relative to those coordinates, then the term that you claim should not be called centrifugal force is mr(W + w)^2, and of course this is the force that we would measure if we were holding the particle with a thread. It seems to me we would have to weave a fairly tangled web to claim that part of this is centrifugal force and part of it isn’t. We could expand the square, and call the W^2 term a centrifugal force and the 2Ww term a Coriolis force, but what would we call the w^2 term? A pseudo-centrifugal force? Or a double-secret-probation force? Bear in mind that all of these are purely fictitious forces, arising only because of the non-inertial coordinates. Anyone who doesn't like the "diagonal versus off-diagonal" criterion for classifying inertial forces as either cenrtifugal or Coriolis should propose a better one. I've provided references to reputable sources supporting my claims. TstoneT ( talk) 18:54, 29 May 2008 (UTC)
(3) Essential Mathematical Methods for Physicists By Hans-Jurgen Weber, George Brown Arfken, Academic Press, 2004, p 843.
(4) Methods of Applied Mathematics By Francis B. Hildebrand, 1992, Dover, p 156.
Since no one is voicing any objections, I go ahead and think about how to incorporate the more complete definition of centrifugal force into the article, hopefully correcting the mis-impression that it pertains only to rotating coordinate systems. TstoneT ( talk) 23:25, 29 May 2008 (UTC)
Brews, he's given citations for the very things that I have been arguing about. Polar coordinates in the inertial frame are the correct and standard way to analyze planetary orbital motion and the best way of elucidating centrifugal force as an outward radial effect.
The section that I put in yesterday was standard textbook planetary orbital theory. I mentioned Goldstein's.
I can only conclude that most of the editors here are schoolboys who have done the basic circular motion theory and are totally unwilling to examine the general cases of curved path motion such as ellipses and hyperbolae and the role of the radially outward centrifugal force.
I would say that my section was erased yesterday for no other reason than that nobody here could understand it since they have never done planetary orbital theory in advanced applied maths at university.
And in true schoolboy style, anything that they can't understand must go to the trash can. David Tombe ( talk) 05:22, 30 May 2008 (UTC)
I think there is one "trick" when trying to show a centrifugal force in polar coordinates. Look at eq. 1.48 in [22].
Here Fr is the "real" Newtonian force, which in the case of circular motion (that is, at constant r) is pointing constantly inwards and equals . That is, the only force is the centripetal force. However, if we say "wait a second, there is a term here, which looks just like Newton's equation for r!", we can rewrite equation 1.48 as (introducing the definition F′ for convenience):
This is exactly what McQuarry did. The problem is that F′ looks like a force for r, but it's not the "real" Newtonian force. So curiously enough, the centripetal force term from eq. 1.48 "changes sign" and turns into the centrifugal force term for Newton's force in a rotating frame. I argue that by insisting in treating F′ like a force, defined as , we are effectively "hopping on" to the rotating frame. That is, like SCZenz said above, just changing the coordinate system does not make the frame non-inertial. What makes it non-inertial is pretending that the product of mass and the second derivative of a coordinate is a force.
However, unlike a frame of reference that is rotating at a constant rate, the polar coordinates are always "following" the object in question. That is why, when cast in terms of polar coordinates, the Coriolis force is always tangential. There is no way of "moving tangentially"--if the object tries to move tangentially, φ speeds up or slows down to follow along, which results in a change of the centrifugal force term instead of a radial Coriolis term (the net effect is the same, of course). -- Itub ( talk) 09:58, 30 May 2008 (UTC)
When discussing a point particle as in the article planar motion, the equation for acceleration arises:
where the coordinate axes are attached to the particle and the radial direction is that of the displacement of the particle from some origin in an inertial frame. Using this formula, one can refer to a Coriolis force, an Euler force and a centrifugal force by adopting the moving reference frame attached to the particle.
This problem and its associated terminology although similar to that of this article, are not the same. This article refers to observational frames of reference and how trajectories described in such a frame are to be compared to those in an inertial frame. That objective is different from following a single particle from an inertial frame and describing its components of acceleration along various directions rather arbitrarily selected. I say arbitrarily selected, because the radial direction selected depends upon the origin of the observer, and will change even within the same inertial frame if the origin is chosen differently. This radial direction is not along the radius of curvature of the path, and its magnitude ρ is not the radius of curvature of the path (except for the very specific case of a circular path around the selected origin of coordinates), and so connection with centrifugal force cannot be made. The other component also is arbitrary as uθ is chosen orthogonal to the arbitrary direction of the displacement vector, and is not tangent to the path (except by accident). Brews ohare ( talk) 21:43, 29 May 2008 (UTC)
No Anome, what matters is the correct matching up of the maths to physical reality, and the polar coordinate system is the one that is tailor made to deal with concepts such as centrifugal force and Coriolis force.
The centrifugal force is a radial effect and the Coriolis force is a tangential effect.
But before we can use the expressions in polar coordinates we must construct a physical model of a real situation and then construct a differential equation around it, usually in the scalar variable of radial distance.
If you were in the slightest genuine about this topic, you would have read the section which I added to the main article yesterday. You would have blocked PeR for vandalism and wikistalking for having erased it on specious grounds.
It hardly needed sourced since it is standard planetary orbital theory which obviously none of you know anything about. In fact I did mention Goldstein's Classical Mechanics.
The picture that I am getting here is that the article has been hi-jacked by a group who have had a basic introduction to circular motion but who would be incapable of handling elliptical or hyperbolic motion and so they will all make sure that no such generalizations appear in the main article.
Your group has indulged in a number of deceitful tactics which I will now list.
(1) Making arguments in polar coordinates but jumping into Cartesian coordinates to conceal the flaws. The main example is circular motion, which is all that you seem to be capable of considering. You accept one moment that there is a radially outward centrifugal force balancing a radially inward centripetal force. But as soon as the centrifugal force becomes inconvenient for you, you claim that it vanishes in the inertial frame, even though the centripetal force remains. That is just a nonsense.
(2) Trying to drag in the three body problem while totally sweeping the two body problem under the carpet. This is because you feel more comfortable in a field that nobody can understand. It is good cover for talking nonsense.
(3) Introducing Lagrangian mechanics.
(4) Introducing Hamiltonian mechanics.
(5) Introducing matrix algebra.
(6) Quoting Feynam.
We have seen all these tactics used in a pathetic attempt to deny the fact that centrifugal force only occurs when a particle actually possesses an angular velocity relative to a point.
The section which I put in yesterday contained partically all that you need to know about centrifugal force. But that was too good for you. You much prefer that big mindless waffle of an introduction that tells us absolutely nothing about centrifugal force. David Tombe ( talk) 05:43, 30 May 2008 (UTC)
User:David Tombe has been blocked for a week for incivility and personal attacks. It is my strong recommendation that people not engage in discussion with him about his latest comments; it is extraordinarily unlikely to contribute to the project. If you must, please use his talk page. -- SCZenz ( talk) 06:34, 30 May 2008 (UTC)
You sir are a vindinctive and nasty person. You have harbored a personal animonisity towards Mr Tombe and your actions reflect your nasty character. You have consistently refused to treat him in a fair and civil manner in your efforts to block a full and objective discussion on these pages. You sir are the problem here, not Mr Tombe. Again I demand that you formally apologise to Mr Tombe for your personal animonisity and bias towards Mr Tombe. Your refusal to comply with past demands to do this demonstrates your personal lack of civility and personal mean spiritedness. You should be blocked from future actions of this nature and that would greatly improve the quality of discussions conducted here with wikipedia editors. It is my informed judgement that Mr Tombe has contributed more than you could possibility appreciate. The subject article is a dreadful mess. It reflects the ignorance of wikipedai editors and their continued resistence to learning the facts by educating themselves instead of repeating nonsense as if it were fact. 72.84.67.168 ( talk) 13:52, 30 May 2008 (UTC)
The equation for planar motion of a particle derived in planar motion:
is discussed by Taylor using the example of circular motion to introduce the notions of centripetal acceleration and what he calls "tangential" acceleration. The case of circular motion is unique however, because in this coordinate system polar coordinates actually are normal and tangential to the trajectory. Consequently, forces normal to and tangential to the trajectory, which have actual physical meaning, happen to be picked up by the polar coordinate system. However, to treat an elliptical path, for example, an elliptical coordinate system is necessary to make the coordinates tangential or normal to the path. If one were to do this, the tangential and centripetal forces could be picked out in this case too.
However, the application of polar coordinates to an elliptical path does not have this property. Consequently, determining the centripetal and tnagential forces in such a case is not straightforward, and attempts to cook it up are doomed to complexity.
Also, in a kinematic discussion, an elliptical orbit does not have to be traversed in the manner prescribed by the inverse square law. It is a perfectly proper application of kinematics to inquire what forces are necessary to traverse an elliptical path with position on the path an arbitrary function of time. Thus, the discussion of elliptical orbits can be divorced entirely from planetary motion for a kinematic discussion.
In the case of planetary motion, the force of gravity is always radially directed toward the Sun. That gives polar coordinates a special place in kinetics, but the connection of this radial force to the centripetal and tangential forces of kinematics is (a) complicated and (b) specific to this particular dynamic arrangement.
In sum, from the viewpoint of fictitious forces, polar coordinates are only special for circular motion, and for any other trajectory their value is moot. Brews ohare ( talk) 16:09, 30 May 2008 (UTC)
This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
The result of the proposal was move. 199.125.109.99 ( talk) 17:14, 1 May 2008 (UTC)
Wolfkeeper, you are wrong. See my reply to Steve above. When nothing is physically rotating there can be no centrifugal force. I think that your belief to the contrary lies at the root of this problem. You are backed up by superior numbers, but I believe that you are wrong.
Yesterday, I drew your attention to the fact that the ω of the rotating frame of reference has to also be physically connected to the tangential speed of the particle. If the particle is sitting still in an inertial frame, then there is nothing doing. The situation is quite different from the situation which occurs in a centrifuge.
This analogy extends to Coriolis force. If a bird flies over a rotating children's roundabout, then the Coriolis force is entirely fictitious. There is no physical connection between the two situations.
But in cyclones in the atmosphere, the moving elements of air are physically connected to the larger entrained body of atmosphere. Hence the effects can be real, as like in the centrifuge. I have been trying to impress this point on Rracecarr but without any success. David Tombe ( talk) 07:52, 29 April 2008 (UTC)
Yes, Wolkeeper, inertia is real. But that is not the argument. The argument is about distinguishing between cases in which the effects are purely fictitious and cases in which the effects are real. David Tombe ( talk) 08:29, 29 April 2008 (UTC)
Wolfkeeper, you still don't understand the difference between the real effect which occurs during actual curved path motion, and the fictitious effect which is observed when a stationary particle is observed from a rotating frame of reference. David Tombe ( talk) 12:18, 29 April 2008 (UTC)
Merge the two articles. There is no good reason to split in two articles; they are about the same effect in different situations. ( TimothyRias ( talk) 11:41, 29 April 2008 (UTC))
Wolfkeeper,That was a complete misrepresentation of everything I have been saying. I am the one that has been saying that the effect in the atmosphere is real. The others, such as Rracecarr are the ones that have been saying that it is purely fictitious. You have been sitting on the fence saying that it is not quite fictitious. David Tombe ( talk) 20:07, 29 April 2008 (UTC)
FyzixFighter, There is nothing in any of my edits which you have deleted that either criticizes the orthodox position on rotating coordinate frames or make the claim that centrifugal force is real.
You have been deleting edits which describe in simple terms exactly what centrifugal force is. It is an outward radial acceleration which occurs when an object moves in a curved path. David Tombe ( talk) 20:15, 29 April 2008 (UTC)
No FyzixFighter, I won't give you a source for that fundamental fact. Children learned it in the garden when they swung a bucket of water over their heads. You have simply shown yourself up here as nothing but a trouble maker. You have stormed in on a wikistalking mission and then decided to go and make accusations against me when I hit back. You are just a trouble maker. You are not here to improve the article at all. David Tombe ( talk) 20:46, 29 April 2008 (UTC)
Wolfkeeper, you should merge the articles. Reactive centrifugal force is a knock on effect which occurs when something that is experiencing centrifugal force knocks against something else. It is not even covered in this article because you have turned cause and effect upside down. and it doesn't really need to be covered at all unless you might wish to write a section on it.
There is only one centrifugal force but there is an argument about whether it is real or fictitious. David Tombe ( talk) 12:35, 29 April 2008 (UTC)
David is correct, there is no fictious centrifugal force and your attempt to invent one to satisfy your confused notions of physics is just a fiction itself. 72.64.49.249 ( talk) 13:20, 29 April 2008 (UTC)
When a bucket of water is swung in circular motion, it induces a hydrostatic pressure in the water. That is an effect which is observed from all reference frames. It is absolute. It is quite wrong to state that centrifugal force is an effect which is only observed in rotating frames of reference.
The closest that you could get to making that statement true would be to say that this effect is called 'centrifugal force' when it is observed from a rotating frame of reference but when it is observed from an inertial frame, the modern tendency is to refer to this effect as having been caused by inertia.
This effect, whether we call it centrifugal force or inertia, is not the same as the situation which we are dealing with when we observe a stationary object from a rotating frame. In the latter case, there is no real effect. These two circular motion situations are every bit as different from each other as two important circular motions in electromagnetism that are connected with the Faraday paradox. When we move a charged particle tangentially in the equatorial plane of a magnetic field, we get an induced electromotive force. But when we rotate the magnet on its magnetic axis with the particle stationary, we only get the artificial circle as observed from the frame of the rotating magnet. Nobody has ever said that these two effects are the same. Likewise in mechanics. There are two different effects and only one of these effects is centrifugal force.
Hence, there should be one single article on centrifugal force. Reactive centrifugal force does not need to be mentioned as it is merely a knock on effect in collisions and contact pressure situations. It can however be mentioned in a section, if somebody so wishes it to be. But I hope they manage to get the action and reaction the right way around.
Now moving on to the maths. If you look at the derivation of the rotating frame equations, you will see that ω which refers to the angular velocity of the rotating frame also refers to the angular velocity of the particle. It is a simple vector triangle. The particle velocity is split into two components. In the limit, this becomes a tangential component connected with ω, and a radial component which comes into play for Coriolis purposes.
Hence, these equations only apply to co-rotation, and to real Coriolis force when the radial velocity is physically referenced to the rotating frame such as in the hydrodynamics of the atmosphere, which of course is why the cyclones are real and not merely apparent.
So how should we proceed with a wording which does not conflict with the textbooks?
Centrifugal force is a term used within a rotating frame of reference, and it applies to the outward radial force which acts on objects which are stationary within the rotating frame. This effect can be extended to all curved path motion.
In the inertial frame of reference, this effect is said to be caused by inertia. David Tombe ( talk) 09:23, 30 April 2008 (UTC)
Steve, you mention about a spin off article for reactive centrifugal force. Do you mean another page? Can it not be handled as a section near the end of a united centrifugal force article?
The so-called reactive centrifugal force seems to have caused the editors to overlook a more fundamental division of effects within what modern textbooks call centrifugal force. This division splits along similar lines as in the Faraday paradox.
There is a real effect which occurs in a centrifuge. That is a radial outward pressure associated with actual curved path motion.
There is a fictitious effect which is associated with a stationary object being viewed from a rotating frame.
Personally, I would only use the term centrifugal force to cover for the real effect. But if the textbooks blend the two together under one set of umbrella maths, then we need to specify these two scenarios as per the Bucket argument. We cannot overlook the physical difference on the ostensible grounds of a unifying maths. That would be like overlooking the difference between the time dependent aspect of the Lorentz force and the motion dependent aspect on the grounds that one single equation covers them all.
We must specify the hydrostatic pressure in the rotating bucket as one scenario, and the stars rotating across the sky as another scenario.
We can have an introduction which sticks to textbook terminologies. But we cannot make the blanket assertion that centrifugal force is fictitious. It is sometimes fictitious and sometimes real.
Editors here have devolved all the real stuff to 'reactive centrifugal force' and deemed the rest to be fictitious. That is not a correct division. There is real centrifugal force before any reactions occur at centrifuge walls. David Tombe ( talk) 18:16, 30 April 2008 (UTC)
Wolfkeeper, If you had read the new introduction, you would have seen that it unequivocally maintained the position that the centrifugal force applies to all objects. I disagree with that, but that is the official position.
You reverted me on the false grounds that I had alleged otherwise.
I haven't got a citation that would explicitly state that the coordinate transformation equations only apply to co-rotation. I can see it just by looking at the vector triangle in the derivation. The particle velocity is split into two components. The tangential velocity of the rotating frame becomes one of those components. Hence the two things are physically linked.
The introduction which I have put in now was carefully thought out to cover all aspects of the controversy.
Read it and think about it before you revert it. David Tombe ( talk) 06:19, 1 May 2008 (UTC)
"To the extent to which the object or fluid element co-rotates with the frame, a radial acceleration or a hydrostatic pressure is induced."
A radial acceleration is always induced everywhere in the rotating frame proportional to distance from the axis. It may or may not be balanced or enhanced by other (pseudo)forces, but it's not a matter of the extent of corotation.- ( User) WolfKeeper ( Talk) 06:21, 1 May 2008 (UTC)
Let's examine the existing introduction. This paragraph here,
In some cases, it is convenient to use a rotating reference frame, rather than an inertial reference frame. When this is desirable, coordinate transformations from the inertial reference frame can be applied.
However, to do this correctly, in the rotating reference frame, a centrifugal force must be applied in conjunction with a Coriolis force for the correct equation of motion to be calculated. The centrifugal force depends only on the position and mass of the object it applies to (and does not depend on its velocity), whereas the Coriolis force depends on the velocity and mass of the object but is independent of its position.
is just clutter.
And it says nothing about any of the real effects that would occur in a centrifuge. Neither does it clarify about not to get confused with centripetal force.
Yet you have nevetheless chosen to revert. Your decision was not based on physics arguments. David Tombe ( talk) 06:32, 1 May 2008 (UTC)
Wolfkeeper, when we rotate a bucket of water, centrifugal force creates a hydrostatic pressure in the water. That is a reality and it only happens in the co-rotation scenario.
At the moment, you are in a state of denial for which there seems to be no cure.
You are living in a fictitious world in which you want to pretend that a rotating bucket of water is exactly the same thing as a stationary bucket of water as when viewed from a rotating frame of reference.
They are not the same thing. It is a centrifugal force version of the Faraday paradox.
I tried to compromise with you and retain the initial line that centrifugal force applies to all the objects.
But you seem to be offended at any suggestion at all that centrifugal force can have any element of reality about it.
You are in denial and you are trying to impose your 'fictitiousist' view of the world on everybody else.
I deliberately worded the article to compromise between the mathematical definition and the layman's understanding. You have reverted it to a version which is clearly ill though out, ommitts important facts, and contains alot of unnecessary clutter.
With my introduction, we won't even need a separate article for reactive centrifugal force. The division is a total mess. David Tombe ( talk) 07:17, 1 May 2008 (UTC)
Wolfkeeper, You are in a state of denial. Hydrostatic pressure exists in a rotating bucket of water. That is not original research and it does not require a citation. If you check the wikipedia rules, you will see that no citations are needed for facts that are obvious.
You adhere to some strange view of the world in which everything is relative and that absolute facts such as hydrostatic pressure in a rotating bucket of water do not exist. You do not live in the real world.
I doubt if you ever thought of the Bucket argument before. And now that you have been made aware of it, you have calmly stated that you are going to ignore it.
You are not in a position to be editing articles on real physics. You have made an absolute shambles of these pages and for some reason, everybody seems to be too scared to stand up to you. David Tombe ( talk) 09:09, 1 May 2008 (UTC)
I've just sent a note to David regarding Wikipedia's Neutral Point of View policy and attribution, verifiability and reliable sources principles. I look forward to him providing suitable cites to support his contributions from now on. -- The Anome ( talk) 11:15, 1 May 2008 (UTC)
Reading this only reinforces the perception that Wikipedia is not a valid source for physics information. The perception of Wikipedia is that it is a source of misinformation, and not a source of correct information. The evident fact is that the editors are unwilling to work out a correct version which incorporates the valid criticism of their attempted edits. Mr Wolfkeeper evidently knows nothing, and denies an experimental fact known for thousands of years to be true. Management has now confirmed that course of action, and validated the view that Wikipedia is more about enforcing certain opinions than benefiting from the criticism of independent scholars and experts. Most physics experts I know consider this web site a joke. Wikipedia is a known bad source of information, due to its policy of copying from others without regard to the quality of the information being blindly repeated. I personally have found so many mistakes here that I dont even attempt to correct them. It is not worth the trouble, considering the editor's attitudes. Sorry, but I do not beleive anything you state regarding physics, since your editiors have shown they dont understand what they are doing. Wikipedia dosen't work, and its failure to take into consideration valid criticism only reinforces the bad information already found here. 72.84.69.81 ( talk) 17:20, 1 May 2008 (UTC)
This edit war will only be resolved when there is an open realization of what the war is about. What is the undercurrent that is driving it? And after making yesterday's edits and watching the response, I can now tell you all exactly what it is about.
I inserted a clause in the introduction which drew attention to the fact that in co-rotation situations, we obtain an actual outward acceleration or an actual hydrostatic pressure. Somebody correctly altered that to 'pressure gradient'. That is what constructive collaborative editing is all about. Somebody else changed 'heavier' to 'more dense'. Very good. That's the right idea. Keep improving the matter and making it progressively more and more accurate.
Now unusually, for the first time, my edits were not completely erased. These key bits of information, rather than being completely erased, were moved to a section further down the page where scan readers are less likley to go.
Compare this to the excessive invasion of the first line with copious references to the term 'fictitious'.
Clearly we have a party here who are very keen to emphasize the word 'fictititious', and to hide any examples that might undermine the suitability of the term 'fictitious'.
As regards the original research which I keep getting accused of, I'm still waiting to have that pointed out.
Now at the moment, the introduction is still most unsatisfactory. But I'm going to leave the first line alone and try and tidy up the incoherent clutter below it.
A member of the public reading about centrifugal force wants to see examples. They don't want to read about transformation equations that might be used by scientists behind the scenes.
And we have no examples in the introduction. All we have is a very amateurish statement to the extent that the matter is confusing. That's the kind of thing that somebody who doesn't understand the issue would write.
I'm going to make a different edit later today. When it gets erased, as it almost certainly will be, then we can discuss why. And I guarantee that it will all come down to the fact that the ruling party do not like attention being brought to the fact that centrifugal force can have real effects. It is being sold in the first line as a 'fictitious' effect and that's the party line which it seems must be upheld at any cost. David Tombe ( talk) 08:29, 2 May 2008 (UTC)
Anome, the terminology has never been the main issue, although it's true that I do not like the term 'fictitious force', and I would indeed prefer the term 'inertial force'.
The main issue has been that any attempt to illustrate any semblance of reality surrounding centrifugal force is swiftly removed from the introduction.
Interestingly, one critic yesterday stated that he agreed with my insertions but then ciricized me for having removed other stuff.
So today, I will reinsert a single sentence and not delete the other stuff. I guarantee it will be swiftly deleted.
Then we can discuss why. David Tombe ( talk) 10:07, 2 May 2008 (UTC)
Anome, the lines which PeR removed related to an effect which is absolute and which doesn't depend on which frame of reference we view it from. That outward acceleration or the associated hydrostatic pressure can be viewed from all reference frames. It is not a fictitious effect. That's why PeR removed it. He doesn't want attention brought to absolute effects in conjunction with centrifugal force. David Tombe ( talk) 11:07, 2 May 2008 (UTC)
Plvekamp, it was actually you who reverted me this time. Did you have a reason to do so? PeR has now informed me that his reason was that I hadn't provided sources. But we don't need sources for facts that are not in dispute.
Are you disputing the facts that you erased? David Tombe ( talk) 13:22, 2 May 2008 (UTC)
We are now getting closer to the truth. Of course centrifugal force and centripetal force act as an action-reaction pair in every circular motion situation.
A web link to Donald E. Simanek saying the opposite is not acceptable.
Anybody who claims that centripetal force and centrifugal force do not form an action-reaction pair in circular motion needs to provide a citation from a peer reviewed journal or a reliable textbook. David Tombe ( talk) 14:00, 2 May 2008 (UTC)
FyzixFighter, The statement that you erased read,
When the wall of the centrifuge applies an inward acting centripetal force such as to prevent further radial acceleration, we will have an action-reaction pair.
The wall acts inwards on the object and the object acts outwards on the wall. That is an action-reaction pair. If you insist otherwsie then you are lying and trying to pull the wool over the eyes of the readers.
Reading your passage above, it is clear that your example doesn't apply to the situation in question, and that you have ended up contradicting yourself. Basically, you haven't got a clue what you are talking about. Your reversion was vandalism. David Tombe ( talk) 16:01, 2 May 2008 (UTC)
FyzixFighter, would you then be willing to reinstate the clause, reworded to your own satisfaction? David Tombe ( talk) 17:06, 2 May 2008 (UTC)
FyzixFighter, I thought that the whole introduction was about things as viewed from the rotating frame. And all I did was give an example of a situation where the radial acceleration was real. And you erased it.
Would you consider reinstating that sentence? David Tombe ( talk) 18:35, 2 May 2008 (UTC)
Plvecamp, Does a co-rotating object accelerate outwards or not? David Tombe ( talk) 17:11, 2 May 2008 (UTC)
If it is free (object in car, particle at top of test tube not encountering resistance):
- From inertial frame: No acceleration, no force, moves in straight line (and approaches end while doing so) - From rotating frame: Acceleration outward in accordance with centrifugal pseudoforce covered in this article
When it encounters restraint (door of car, particle encountering resistance or at end of test tube)
- From inertial frame: Centripetal force exerted by restraint on object, object accelerates radially inward - From rotating frame: No acceleration, object is stationary if frame rotates at same speed as constraint
Plvekamp ( talk) 17:28, 2 May 2008 (UTC)
This is so outrageous - "I don't need to specify a frame of reference" - that I'm at a loss for words. That has to be the most naive statement you've uttered yet. If you actually believe that, then nearly all of mathematical physics is beyond your understanding.
Plvekamp (
talk) 18:02, 2 May 2008 (UTC)
A link to Simanek's site is quite acceptable. He is a physics professor, after all. Mangoe ( talk) 16:55, 2 May 2008 (UTC)
Who is this guy??? Please explain which link is the link you are talking about. When you write something you need to be clear about what you mean. —Preceding unsigned comment added by 72.84.70.6 ( talk) 20:55, 3 May 2008 (UTC)
Steve, we'll continue this in a new section. You left off at,
Steve, I'm quite familiar with orbital theory concerning hyperbolas, parabolas, and ellipses. I've had to solve many a difficult problem in this field.
Let me begin with a very simple example. Consider an object high above the Earth that has got zero tangential speed. The only force acting will be gravity, radially downwards. The object will accelerate downwards and the acceleration due to gravity will be equal to r double dot.
Now consider a circular orbit. There will be an additional outward centrifugal force given by mv^2/r. In this case, r double dot will be equal to zero. There will be no net radial force or acceleration.
In elliptical orbits there is a constant oscillation between whether the centrifugal force is greater or the gravity force is greater.
If we consider an ellipse in polar coordinates, centered on the focus, and solve it, we end up with exactly two radial accelerations. There will be an inverse square law acceleration inwards, and a v^2/r acceleration outwards. Centrifugal force is a very real thing.
Now lets get to the point. Your problem with all this is that it contradicts the pet theory that is being pushed on these pages by the 'Fictitious Party'.
That theory is that when an object is at rest in the inertial frame, it will be seen to trace out a circular motion when viewed from a rotating frame. Your argument is that there is a net inward fictitious centripetal force which is the sum of an outward centrifugal force and an inward Coriolis force which is twice as strong.
You will agree that this is the pet theory that the 'Fictitious Party' are trying to promote on these pages. Indeed there was once an entire section devoted to this idea on these pages. It was considered to be much more important than examples of the real effects which your colleagues are currently at this very moment in time trying to hide.
Your theory is wrong to the backbone on a number of counts.
(1) The transformation equations for rotating frames, only apply to co-rotation. This is clear when we look at the derivation. The angular velocity term ω which is ostensibly the angular velocity of the rotating frame, is in fact tied in with the tangential velocity of the particle in question. This is clear by virtue of the fact that it is one of two components of the particle velocity.
(2)In the limit, the v term then becomes the radial velocity. Hence there is no Coriolis force in the radial direction. The Coriolis force and the centrifugal force can never act in the same direction because they are two mutually perpendicular aspects of the same thing. Hence the idea that the Coriolis force could be producing an inward radial force is absolute nonsense.
(3)Even if we ignore points (1) and (2), the final result comes out to be a net inward radial acceleration. That is not circular motion. Circular motion requires a net zero radial acceleration.
So the pet theory of the 'Fictitious Party' is wrong.
When an object is stationary, nothing happens. There is no centrifugal force. There is no hydrostatic pressure gradient induced in a bucket of water.
Those things only happen when the object co-rotates.
And at the moment, your colleagues are desperately trying to hide any references to situations involving co-rotation that result in real physical effects.
There is a group of them who are winning on numbers but who clearly haven't got the first clue about physics but seem to presume that they have.
I would have thought that you would have been intelligent enough to see right through all this, unless perhaps you have got some vested interest in playing along.
But it is all one big fraud. David Tombe ( talk) 17:37, 2 May 2008 (UTC)
Please see above where David told me "I don't need to specify a frame of reference" when I asked him which frame he was referring to. Make your own conclusions. Plvekamp ( talk) 18:43, 2 May 2008 (UTC)
FyzixFighter, in your number (3), why did you drop the radial velocity component r dot r hat?
By the way, I can also recommend prolonged contemplation of this animation. -- The Anome ( talk) 18:55, 2 May 2008 (UTC)
Yes, I saw that. We must have cross wired. See my full reply above. David Tombe ( talk) 19:07, 2 May 2008 (UTC)
FyzixFighter, before your equation (4) can have any meaning, we have to account for all the terms. Let's forget about the 'theta hat' terms because we are not interested in angular acceleration.
Now supposing the circular motion was a gravity orbit. Where do you see the inverse square law gravity term fitting into equation (4)? Does it go to the general acceleration term on the left hand side, or does it go to the r double dot term on the right hand side? David Tombe ( talk) 20:06, 2 May 2008 (UTC)
Steve and FyzixFighter, it would be a help if the two of you discussed this together and appointed a spokesman to ask me the questions.
Equation (4) tells us nothing until we know exactly what scenario we are applying it to and what the forces involved are. I asked FyzixFighter were he wanted to put the gravity force if it were a circular gravity orbit, and I didn't get a clear response.
Lets then deal with an easier situation. Let's deal with a weight being swung around on the end of a string. We use the symbol T to represent the inward tension. Can you please present me with equation (4) as per this scenario, showing me where you have inserted the tension T. David Tombe ( talk) 06:45, 3 May 2008 (UTC)
Steve, I'm going to ignore the issue of whether we talk about force or acceleration. We are talking about inertial forces here so it is quite irrelevant.
Now can we get to the key point. You are quite wrong in thinking that the v^2/r term is centripetal force. How could it be? How would a general expression for acceleration suddenly produce a centripetal term in conjunction with a Coriolis term? The parent inertial term vXω expands in two mutaully perpendicular components in polar coordinates. One is the Coriolis term and the other is the centrifugal term. In fact it is quite ridiculous to think that it could possibly be referring to the centripetal force.
Let's consider how that equation is used in orbital theory. The term that you think is a centripetal term is brought over to the left hand side to join the gravity expression. Hence gravity will have a negative sign and the term that you think is the centripetal term will have a positive sign. on the right hand side, we have r double dot.
So we have a second order differential equation in r.
If r double dot is zero, then the gravitational force inwards is exactly cancelled by the centrifugal force outwards.
If you are correct, it would imply that centripetal force is something that occurs naturally. That is not so. The gravitational force IS the centripetal force in this situation, and the v^2/r term is the centrifugal force. David Tombe ( talk) 03:22, 4 May 2008 (UTC)
David, I think I've come to understand a key yet subtle point of disagreement. This is an honest attempt to understand how you understand the physics; I think we might be disagreeing on how we define radial acceleration. So let me set the stage. This is a stationary frame described by polar coordinates. We have an object move in some arbitrary fasion in this frame, and whose position is defined by the coordinates and . In this case, what is the proper expression for the radial acceleration, defining the radial acceleration as :
Or do you disagree that the radial acceleration should even be defined as ? -- FyzixFighter ( talk) 04:41, 4 May 2008 (UTC)
FyzixFighter, I'm sorry but you're very badly mistaken here. The equation that I wrote out is the central force orbital equation. That is the equation that is used to solve central force orbital problems. I solved many a complex problem using that equation.
The equation which you have used is a general acceleration equation derived from a position vector using vector calculus theorems and notation. Whereby I have always been impressed by the amount of information that this equation reveals, we can not allow a quibble about terminologies to alter the reality of the final central force orbital equation.
Your equation effectively exposes the fact that centrifugal force is inherent in straight line motion as viewed from polar coordinates. In fact, I ought to draw the attention of Brews to that point.
But there is no further argument regarding the form of the orbital equation. One side contains a second order time derivative of the radial distance and the other side contains an inward gravity force and an outward centrifugal force. You can call that second order time derivative whatever name you like. But in circular orbits, it will be zero.
And if you try messing around with the signs in the orbital equation, you will no longer have the orbital equation. If you want a conic solution, then that is the equation. David Tombe ( talk) 08:56, 4 May 2008 (UTC)
Plvekamp has finally responded,
From a rotating frame, the person is accelerating toward the car door.
Now the whole introduction is about centrifugal force which it claims is a force only ever viewed from a rotating frame.
I added a line saying that in situations of co-rotation, an object accelerates radially outwards.
Plvekamp erased this sentence on the specious grounds that this true fact didn't agree with the references.
What references was he talking about? Was he referring to all the references that were wheeled in to enforce the fact that the term 'fictitious' is widely used?
So can we conclude that Plvekamp sacrificed reality in order to comply with the references?
If a centrifuge proves to us that centrifugal force is a real and absolute effect, but the references tell us that this shouldn't be so because the force is question is only a fictitious force, then rather than question the references, we should be better to erase the sentences that draw attention to these inconvenient truths.
Plvekamp, it's about time that you opened your eyes a bit to what's going on in the world around you. David Tombe ( talk) 20:17, 2 May 2008 (UTC)
If you weren't denying those phenomena, then why did you erase mentions of them in the introduction? David Tombe ( talk) 06:27, 3 May 2008 (UTC)
I will no longer respond to your goading, David. Plvekamp ( talk) 12:12, 3 May 2008 (UTC)
David, is there any conceivable argument that might convince you that you are wrong, or are you simply committed, as is suggested by your most recent response above, to promulgating the WP:TRUTH as you see it?
The reason everyone else in this discussion appears to disagree with you, whilst all agreeing with one another, is that they are describing the apparent phenomenon of "centrifugal force" in rotating non-inertial frames in terms of inertial effects within standard Newtonian physics. This has been the standard physical interpretation of this phenomenon for several centuries, and is not likely to change. On reviewing this very lengthy discussion, I can see that this has been explained to you over and over in many different ways, carefully and politely, by numerous different people, with only you taking the dissenting position.
You are unlikely to succeed in ever getting your views represented in the article if you continue in this way. Here's why.
Wikipedia is a tertiary source; it summarizes the information in secondary sources, such as peer-reviewed scientific papers, physics textbooks, and other texts written by qualified physicists. It is not a mechanism for determining the WP:TRUTH; we accept that people disagree about just about everything, and we try to reflect this in our articles. For this reason, we have a set of ground rules for editing here which explicitly try to avoid determining truth here on Wikipedia, relying instead, wherever there is controversy, on restricting ourselves to opinions which can be attributed to external, verifiable, reliable sources.
If you want to change the article, and have your changes kept, you must, like every other editor here, abide by Wikipedia's basic ground rules, namely
Furthermore, we have another requirement: that editors conduct themselves according to our civility policy. Statements that imply that other editors are acting in bad faith, lack intelligence, or are conspiring against you, go against that policy. Repeated breaches of the civility policy may result in accounts being blocked from editing.
Unfortunately, a personal conviction, no matter how strong or sincere, that your views are the WP:TRUTH does not override these policies and guidelines. -- The Anome ( talk) 21:53, 2 May 2008 (UTC)
Anome, you know perfectly well that the edits that I made yesterday were not about ideas that are contrary of current theory. I drew attention to the actual acceleration that occurs outwards when an object co-rotates with a rotating frame. An example would be a passenger in a car getting swung to the side door as a car goes round a corner.
You know fine well that that was not a controversial sentence. You are misrepresenting the situation by continuing to imply that I was trying to insert controversial clauses into the article.
Plvekamp, PeR, and FyzixFighter removed that sentence because they are uncomfortable with the truths inherent in it. Their actions were essentially vandalism which you could have prevented but you chose not to do so. David Tombe ( talk) 12:39, 3 May 2008 (UTC)
Anome, I'm not going to bother. That wasn't the issue. I have no intention of going to search for a citation for such a trivial and undisputed fact. It wasn't erased because there was no citation. That was just the cover story. It was erased for other reasons, and the point was proved.
By the way, I am watching your efforts to re-word the introduction. Note what Woodstone says over on the Coriolis force talk page.
There seems to be a school of thought that is saying that the term fictitious actually means that it refers to a mathematical term which comes into effect only in the accelerated frame (in this case, the rotating frame) as an alternative way of describing real effects.
I don't think that that is the universal interpretation of the term fictitious. I think you will find that some of the editors here will try and slowly but surely graft it back to the extent that it literally means that the effects can only be viewed in the rotating frame.
If what you are saying is true, RRacecarr and PeR wouldn't have cocnsistently reverted my removal of the word 'apparent' on the Coriolis page.
I would perhaps tend to agree with your amendments if I am interpreting you correctly. You are saying that these effects are real but best dealt with mathematically by what we term 'fictitious forces'. If that is so, I think that you will also agree with me that the term 'inertial force' is infinitely superior. David Tombe ( talk) 15:28, 3 May 2008 (UTC)
PlveKamp, I think that the big problem that we are up against is that the modern textbooks are pushing these mathematical transformation equations in a way which disguises a very important difference between two completely different situations. These two different situations are described in the famous Bucket argument.
My natural inclination would be to view centrifugal force as a convective force. In other words it is a force which comes into existence at right angles to the direction of motion of a particle moving in a curved path. And that the effects, which are now described to be real, in the introduction are only effects which have come into existence BECAUSE the object is engaged in a curved path motion.
At the moment, the introduction is now admitting to real effects. It was never actually an issue in the edit war about whether or not these real effects could be explained in different ways in different frames.
Initially, I was arguing against a party which were adamant that these effects were entirely fictitious and could only be viewed in the rotating frame.
Finally by pushing the issue of the centrifuge which clearly disproves such a fictitious outlook, the reality of these effects was finally acknowledged. However, in a sense it is being whitewashed by pointing out that centrifugal force is a fictitious force by virtue of the fact that it is merely an appropriate way of describing effects in a rotating frame which could be described by other means in the inertial frame.
This is an improvement. But it still lacks the most important clause of all.
That clause is that centrifugal force is about real radial effects which come about BECAUSE of curved path motion.
Unfortunately the interpretation of the maths that these guys are pushing is indeed the official line. I did it myself many years ago in applied maths and I can confirm that.
The maths itself is correct. But they are interpretating it such as that ω^2r means that the centrifugal force acts on any body in a rotating frame.
I am adamant that the ω term is telling us that it only applies to objects that themselves have that ω. And the fact that a centrifuge only works for co-rotation would tend to back that idea up.
It would seem however that what they are preaching is indeed what is being preached in the universities.
So there's not really very much that anybody can do to help the situation. The first line in the introduction messes it all up from the outset.
I would have liked a line that drew attention to the absolute reality of co-rotation situations. That is essentially what the recent stage of the edit war was about.
But at the end of the day, there is no doubt that fictitiousism is in the ascendency at the moment.
I have just heard that sometime in the early 1950's the textbooks on orbital theory switched the centrifugal force term in the equations into centripetal force.
So really the problem is too far gone now for anybody to be able to do anything about it. David Tombe ( talk) 17:53, 3 May 2008 (UTC)
Brews, in Cartesian coordinates, the centripetal force shows out alone as you say. I am totally familiar with the derivation. We take two velocity vectors on the arc of the circle and make a vector triangle. This leads to an inward pointing acceleration of value v^2/r.
But you are overlooking something very important. This centripetal acceleration is with reference to the straight line path that would have occured had the centripetal acceleration not been there.
This straight line path is in fact inertia. Now do that exact same vector triangle again using the straight line path referenced to the exact same point. This time you will get an outward acceleration of v^2/r. In other words, the centrifugal force is implicit in the inertia.
In polar coordinates, we only consider the radial direction, and in that case inertia becomes centrifugal force. David Tombe ( talk) 06:25, 3 May 2008 (UTC)
Brew's, if you can derive centripetal force, just repeat that derivation, but this time instead of considering the velocity vector as having changed its direction in relation to the Cartesian frame, consider it to have changed its direction outwards in relation to the radial vector. You will get exactly the same expression outwards and it applies to straight line motion in the Cartesian frame. Inertia IS centrifugal force.
There is another way of looking at it. Consider the general central force orbital equation. Gravity and centrifugal force combined yield a conic section. In the extreme case of when the gravity is negligible, we get a highly eccentric hyperbola. This is effectively a straight line.
In other words, centrifugal force acting alone leads to a straight line.
Centrifugal force in conjunction with centripetal force leads to a circular motion.
Conclusion. Centrifugal force is always there in the outward radial direction in circular motion, but in the Cartesian frame it is masked as 'inertia'. David Tombe ( talk) 15:12, 3 May 2008 (UTC)
No Brews, let's consider the case when there is no centripetal acceleration and the particle moves in a straight line.
Now do that same vector triangle again referenced from the centre of that same circle that you would have used if there had been centripetal force.
This time you will discover a net outward direction changing acceleration.
In other words, the centrifugal force is there all along but disguised in the straight line motion which is inertia. It doesn't show up in the Cartesian analysis. But it is there.
Now go into polar coordinates and if we have circular motion, the centripetal force inwards will be exactly balanced by a centrifugal force outwards.
Consider an elliptical orbit. Consider the stage when the object is closing in on the centre. According to you this closing in is a consequence purely of the one and only inward acting centripetal force. And based on the expression for gravity (inverse square law), you might think that the fact that the gravity is getting stronger as it gets closer, would mean that it should spiral in even more so.
But it doesn't. At some stage of the orbit, it starts to go up again. What is that radially outward force that suddenly overcomes gravity? David Tombe ( talk) 17:28, 3 May 2008 (UTC)
Brews, if we treat the straight line path from a Cartesian perspective, then the acceleration is zero if it has constant speed.
But if we treat it as measured radially from a fixed point, then it reads a centrifugal acceleration outwards of v^2/r.
Imagine an object going in a straight line with constant speed in the Cartesian frame. Imagine a lamp post which is not on its path.
At some stage the object will be getting progressively closer to that lamp post. Then a point of nearest distance will be reached and the object will then begin to get further away. If we consider the distance between the object and the lamp post, the second time derivative of that distance will be v^2/r away from the lamp post, where v is the component of the actual speed that is perpendicular to the radial vector. In other words, the maximum centrifugal force will occur at the point of nearest approach.
This is a central force orbit. The lamp post exerts negligible gravity and so the solution is a highly eccentric hyperbola which is efectively a straight line.
That is inertia and it is centrifugal force too. David Tombe ( talk) 18:46, 3 May 2008 (UTC)
Brews, in the scenario that I have given you, the direction of the position vector will be constantly changing and so it will be accelerating when viewed in that coordinate system. David Tombe ( talk) 06:16, 4 May 2008 (UTC)
Wolfkeeper, if you have failed to see the link between Kepler's law of areal velocity and the "2 times r dot theta dot" term in the tangential component, which is Coriolis acceleration, then it would appear that you really do have some fundamental misunderstandings of this topic. There is no angular acceleration involved in central force orbital theory.
While you are attempting to back up Steve and FyzixFighter, you are actually saying things that contradict them.
I suggest that the three of you get together to appoint a spokesman so that you can speak with a united voice and we can then bring this argument to a definite conclusion. David Tombe ( talk) 09:54, 3 May 2008 (UTC)
Plvekamp, this is what I mean by the whitewash. This line here sums it all up,
The results obtained by considering these pseudo-forces to be "real" within the rotating frame are identical to those given by calculations made in the inertial frame without them.
That line totally fails to address the fact that the most important aspects of centrifugal force, such as getting thrown to the side door of a swerving car, actually arise BECAUSE of the rotation.
The whitewash line evades that issue totally and acts as if we have these effects that just happen to be going on and we have different ways of describing them in different frames of reference. It misses the entire point of what centrifugal force is about in the name of trying to reconcile two conflicting viewpoints over whether centrifugal force is real or fictitious. David Tombe ( talk) 18:04, 3 May 2008 (UTC)
This would not have been a problem if the article had not defined the centrifugal farce as fictious. So you need to say real, to distinguish it from fictious. Fictious means not real or imaginary. Pseudo means false. The confusion is on the part of the people who use these terms to discuss physics. I say again that the editors, and this means Mr Anemone, you dont understand physics, and this article on the centrifugal farce should be deleted from wikipedia since you will never get the physics right in this discussion.
72.84.70.6 (
talk) 20:28, 3 May 2008 (UTC)
Anome, You've missed the point entirely. Centrifugal force is an effect which comes about BECAUSE of rotational motion. Spin an object and a centrifugal pressue will be induced.
It has got nothing to do with how we describe it in different frames of reference.
At the moment, the article begins by stating that centrifugal force is fictitious and that it is only apparent in rotating frames.
The article then continues by contradicting this and stating that there are real effects but that they would be there anyway whether there is rotation or not. Wrong.
The article then mentions that the centrifugal force that involves actual outward motion, which would be what people have in mind when they look up an article on centrifugal force, is not the centrifugal force that is dealt with in this article.
And it finally ends by stating that the whole matter is very confusing.
Anybody reading this introduction would simply say 'what?'. And they would be less wise about centrifugal force than before they read it.
I'm going to put in a qualifying clause regarding the necessity of the real effects to be induced by rotation. If this clause is deleted, which I am sure it will be, then I can only conclude that the person who deletes it has got absolutely no comprehension of the topic whatsoever.
In fact if I had been the one that had put in what you put in, it would have been deleted already because these people are not even happy with the idea of real effects at all.
But when it was deleted, somebody who would have deleted it if I had been the author, actually restored it.
It is clear from observing the activities on this page, that there is a certain group who revert according to who made the edit, rather than what the edit involved. David Tombe ( talk) 03:47, 4 May 2008 (UTC)
No Wolfkeeper, the Coriolis force does not occur in the natural state of affairs, but the centrifugal force does. This is a direct consequence of Kepler's law of areal velocity which eliminates the Coriolis force and the Euler force from planetary orbital motion. Everyday straight line motion is a special case of planetary orbital motion. David Tombe ( talk) 15:43, 5 May 2008 (UTC)
Dbachmann, the confusion is not all mine. The confusion is all yours for failing to be able to see that actual rotation induces real radial effects, whereas no effects at all are induced on a stationary object whether it is observed from a rotating frame of reference or not. David Tombe ( talk) 09:18, 5 May 2008 (UTC)
Does it only appear that his bones are broken? 119.42.68.141 ( talk) 10:09, 9 May 2008 (UTC)
From the McGraw Hill Dictionary of Mathematics and Physics centrifugal force: (1) An outward pseudo-force, in a reference frame that is rotating with respect to an inertial reference frame, (2) The reaction force to a centripetal force. —Preceding unsigned comment added by Denveron ( talk • contribs) 04:48, 4 May 2008 (UTC)
One of the requirements of scientific thinking is that the terms used in science have a definite and clear meaning and that there is an economy of terms used. This is not the case in modern physics which has multiplied a profusion of confusing and ambigous terms to discuss centrifugal force. There was no problem with this definition for several hundred years. Yet now, one can not read a physics book without being subjected to a multitude of ambigous confusing and absurd definitions that basically are meaningless metaphysical entities which contribute nothing to the understanding of the physics involved. The fact that wikipedia can not make sense out of this centrifugal farce demonstrates the useless aspect of these absurd terms. Wikipedia editors dont know what these terms mean and they cant explain them here, so you should call this article the centrifugal farce. The article should be entirely deleted since you will never get it right. 72.84.66.108 ( talk) 15:04, 4 May 2008 (UTC)
Sheffield Steel, I have been advocating that very point. There is no need to mention rotating frames of reference at all. It merely provides a mechanism within which to perform conjuring tricks with the maths. It obscures the underlying reality of the fact that centrifugal force only occurs when actual curved path motion happens.
In relation to your reply to 72.84.66.108, can you please tell us all exactly what outdated and incorrect ideas you have in mind. From what I can see, he is saying the same as me, which is that we need to have co-rotation in order for centrifugal force to occur. Is that an outdated and incorrect idea? David Tombe ( talk) 09:15, 5 May 2008 (UTC)
What I got from the above pages of chatter was that the Introduction was too geeky - not everybody is a mathematical aficionado. So to please David and provide a bit broader attack on the subject than "coordinate transformations" I rewrote the first few paragraphs. I know it's presumptuous of me, but somebody said it's easier to revise something than to look at a blank page. So go for it. Brews ohare ( talk) 06:19, 4 May 2008 (UTC)
You must be joking. The entire article is a morass of confusion, and you are complaining about a small attempt at clarification. The article is nonsense as it stands and the attempts to sort out the confusion by imposing more rigorously defined nonsense is a joke. 72.84.66.108 ( talk) 16:52, 4 May 2008 (UTC)
This subsection should be deleted. What is not a rant is either repetitious or unsupported. Brews ohare ( talk) 16:04, 4 May 2008 (UTC)
'Rotating frames of reference' only clouds the entire issue. The key point which is being consistently swept under the carpet is the fact that the transformation equations only apply to co-rotating objects. If there is no co-rotation, then nothing happens.
It is clear that this entire mess is a result of total denial of this fact. I have looked through the edits of the last day and I can see that Virginia anonymous has been trying to push this same point, but that just as when I do it, it gets deleted immediately.
It seems to me that it is much more important to all of you to emphasize trivial facts, such as 'These real effects can also be described equally well in an inertial frame', than to mention the most important fact of all which is that these real effects are actually induced by the rotation itself.
Recently we saw the parent force for both the centrifugal force and the Coriolis force. It takes the form vXω.
The manner in which the editors here have been trying to present this very real inductive effect would be analgous to trying to explain electromagnetic induction as follows,
As viewed from the frame of reference of a rotating bar magnet, an electric current is seen to be induced in a nearby electric circuit. This effect can be equally well described from the inertial frame.
I'm sure that you would all agree with me that it would be the height of nonsense to explain electromagnetic induction like that because it misses out on the most crucial aspect of all which is that the induced electric current occurs BECAUSE the bar magnet is rotating.
You are all doing exactly the same in this article. You are all denying the underlying induction aspect that is caused by absolute rotation.
So if you guys are going to insist on deleting all references to the importance of co-rotation, then you will all remain confused for a very long time. David Tombe ( talk) 08:58, 5 May 2008 (UTC)
No Wolfkeeper, it doesn't. A stationary object in the inertial frame experiences no physical effects by virtue of being observed from a rotating frame. David Tombe ( talk) 15:19, 5 May 2008 (UTC)
I notice that there is now a section entitled 'Is centrifugal Force Real?'.
Well at the beginning of the edit war, I mentioned that Newton, Maxwell, and Bernoulli had believed it to be real. I even provided references. But that true fact was instantly deleted. The 'Fictitious party' are not even comfortable with any mention of the fact that centrifugal force was once believed to be real by the great masters of physics.
You can read this interchange with PeR at the beginning of the edit war and make up your own minds,
David, The centrifugal force was never considered to be real by Newton, Maxwell, or Bernoulli. If you want to put a statement like that you need to cite a source. Specifically you need to cite a source that says "the centrifugal force was considered to be real", or something very similar to that. If you read a text by, say Maxwell, and interpret that as him saying that the centrifugal force is real, that is still original research, since it is your interpretation of what he says. --PeR (talk) 17:16, 20 April 2008 (UTC)
Reply: Admissibility of Evidence
PeR, I think that you are going to have to repeat yourself. We need to get something straight here regarding the issue of admissibility of evidence. You declared that centrifugal force was never considered to be real. You further went on to state that if I were to produce any quotes from Newton or Bernoulli which indicated that they believed that centrifugal force was real, that this would not be deemed to be admissible evidence on the grounds that it would be my own original research. Here is a quote from Bernoulli out of the ET Whittaker book on the history of aethers.
"The elasticity which the Aether appears to possess, and in virtue of which it is able to transmit vibrations, is really due to the presence of these whirlpools; for, owing to centrifugal force, each whirlpool is continually striving to dilate, and so presses against the neighbouring whirlpools."
And here is a quote from Maxwell's paper 'On Physical Lines of Force',
"The explanation which most readily occurs to the mind is that the excess of pressure in the equatorial direction arises from the centrifugal force of vortices or eddies in the medium having their axes in directions parallel to the lines of force"
And you are trying to tell me that this is not evidence to suggest that Bernoulli and Maxwell believed that centrifugal force was real?
YES! I am trying to tell you that this is not evidence to suggest that Bernoulli and Maxwell believed that centrifugal force was real. However, if you don't want to accept this you don't have to. Just don't write anything in the article. If you do want to write something like that then you must (and here I am repeating myself, as requested) cite a source that says "the centrifugal force was considered to be real" or something very similar to that. If you read a text by, say Maxwell, and interpret that as him saying that the centrifugal force is real, that is still original research, since it is your interpretation of what he says. --PeR (talk) 19:42, 21 April 2008 (UTC)
reply: PeR, There is a controversy about whether or not centrifugal force is real. The official position today is that it is not real. The current introduction is abominable because it tries to fudge the issue by pretending that there are two centrifugal forces. One for the realists, and one for the fictitiousists. This is an extreme case of ecclecticism. The current introduction cannot remain because it is a total disgrace.David Tombe (talk) 08:02, 21 April 2008 (UTC)
He replies. You misinterpret what it says. However, the fact that you don't understand it is evidence that it is not clearly enough written, so I agree that it should be rewritten. --PeR (talk) 19:42, 21 April 2008 (UTC)
David Tombe ( talk) 09:33, 5 May 2008 (UTC)
Brews, when actual co-rotation occurs, the centrifugal force is (1) real, (2) radial, and (3) it can be observed from all reference frames. It is an absolute effect.
When there is no co-rotation, then there is nothing. There is no centrifugal force. There are no physical effects in any reference frame. David Tombe ( talk) 15:17, 5 May 2008 (UTC)
David, when your talking about what "a person sit in a car driving in a circle" experiences, you are implicitly specifying a frame of reference. Namely, what a person experiences can only be described in a co-moving frame. Such a frame is typically non-inertial and will thus contain psuedoforces (or however one wishes to call them) from the perspective of this observer/person these forces are very much real. As you state the person feels himself pushed towards the outward door. An other observer will understand this diffently. An observer from an inertial frame will see the person in the car being forced to move in a circle by force exerted on him by the car.(TimothyRias (talk) 14:32, 5 May 2008 (UTC))
If you want to argue from ancient references, please take a look at Newton's Principia Book 1 and Euler's Mechanica Chapter 5, in which curvilinear motion is discussed. Neither author finds it necessary to use centrifugal force; but centripetal force is ubiquitous. Why is that? (Clue: the analysis in both cases uses inertial frames of reference.) Additionally, why do modern physicists also mention centrifugal force in their articles, but yet, none of them here on Wikipedia agree with your interpretation? There must obviously be a cabal, since you have the WP:TRUTH. Plvekamp ( talk) 15:49, 5 May 2008 (UTC)
David, instead of just stating that people are completely confused, you might try and use actual arguments. Our at least try to understand other people's arguments. And actually the centrifugal force induced on the man in the car is only perceived in the co-moving frame. And observer in an inertial frame will only perceive one force acting on the man in the car and that is the force exerted on the man by the car. (well if you would also count gravity that would be two, but that is really beside the point) ( TimothyRias ( talk) 20:56, 5 May 2008 (UTC))
David, you are missing my point. Sure the seat in the car is exerting a force on the person in the car causing him to follow its movements. My point was that if viewed from an inertial frame this is the only force acting on the man even when going around a corner. When the car is driving around in a circle at constant speed the force exerted on the man by the car is completely radially inward. (I'm neglecting gravity here for the moment for convenience of speech) ( TimothyRias ( talk) 07:48, 6 May 2008 (UTC))
No David he would not! If what you say would be true, then the person on the street would see the person in the car make a curve in the opposite direction of the car. We all know this to be false, the person will move in a straight line as seen from the street. ( TimothyRias ( talk) 08:18, 6 May 2008 (UTC))
No Timothy, the person in the street sees the passenger move in a straight line in the Cartesian frame, but he also sees the passenger moving out radially towards the side door in the rotating frame. He can see both frames at once. David Tombe ( talk) 08:44, 6 May 2008 (UTC)
Timothy, I was only describing it all in one frame at a time. The centrifugal force occurs radially when the passenger is subjected to a tangential motion. You can consider that effect real or fictictious. It's up to you. But one thing is sure. It only occurs when the passenger has a tangential velocity. It does not occur on objects that are not co-rotating with the car. David Tombe ( talk) 13:32, 6 May 2008 (UTC)
Yes, Timothy. And the ball would also have centrifugal force in relation to the centre point of the car's circular motion. The actual factor that induces centrifugal force is 'tangential velocity relative to a point in space', and the centrifugal force is a radial force measured relative to that point.
Co-rotation in a rotating frame of reference is only one particular scenario that brings about centrifugal force. It is not the most general scenario. When I said above It does not occur on objects that are not co-rotating with the car., I was specifically referring to stationary objects. David Tombe ( talk) 04:25, 7 May 2008 (UTC)
This is copied from above:
--- Brews, when actual co-rotation occurs, the centrifugal force is (1) real, (2) radial, and (3) it can be observed from all reference frames. It is an absolute effect.
When there is no co-rotation, then there is nothing. There is no centrifugal force. There are no physical effects in any reference frame. David Tombe ( talk) 15:17, 5 May 2008 (UTC)
Wolfkeeper, You have changed the context. In my original discussion with Brews, I was saying that in straight line motion in the inertial frame, centrifugal force is built into that motion in the form of inertia. If we measure the second order time derivative of radial distance from a fixed point, we will get v^2/r where v is the component of the velocity that is perpendicular to the radial line.
You tried to cloud the issue by introducing Coriolis force. Coriolis force is not involved in that scenario. Kepler's laws have eliminated Coriolis force from planetary orbital theory.
You then went on to introduce a rotating frame of reference scenario which would indeed involve fictitious tangential effects. David Tombe ( talk) 07:49, 6 May 2008 (UTC)
Lets derive those equations shall we. Lets consider a particle moving in a rotating frame rotation with angular speed . At any time the kinetic energy of this particle will be given by . The corresponding action is By the action principle the variation of this should vanish
This implies the equation of motion:
which is equivalent to the transformation formula present in the article. From this derivation it is manifest that can take any vector value, and is independent of . In particular, is not radial as you have been claiming. ( TimothyRias ( talk) 09:07, 6 May 2008 (UTC))
I did no such thing. I subtracted a vector and then took the norm. The vector I subtracted has no relation with whatsoever, it is just a position based factor having to do with the fact that we are describing the physics in a rotating frame. Really, start listening to the people with actual degrees in physics that understand what they are talking about. ( TimothyRias ( talk) 09:26, 6 May 2008 (UTC))
Timothy, Yes, I see what you have done now. It is indeed an arbitrary velocity. But I can't see how you have linked that arbitrary velocity to the velocity term in the transformation equations. I simply don't follow your arguments above. There is absolutely no need to introduce that kind of mathematics to the problem. You are beginning at a very strange point. You begin with the general expression for kinetic energy for a particle in a rotating frame of reference. Correct. But then you introduce a potential energy term that is not needed. After a few manipulations which I simply don't follow, you conclude that it all implies the relevant transformation equations. You would need to show what all the maths terms mean at each stage of the derivation. Those same equations can be derived much more transparently in such a way that we can clearly see that the velocity term has to be the radial velocity. Why did you choose to introduce all that unnecessarily complicated maths above? There was absolutely no need for it. The point has been proved with a much more simple maths. So it can hardly be disproved just by introducing more complicated maths. David Tombe ( talk) 13:25, 6 May 2008 (UTC)
To me this one of the simplest ways to derive the EoM in a rotating frame. You haven't provided any "proof" of your statements. Here I have provide a simple proof that transparently disproves your claim. If this already goes above your head, you might want to reconsinder meddling in something that you clearly do not understand completely. ( TimothyRias ( talk) 14:05, 6 May 2008 (UTC))
Timothy, Hamiltonian and Lagrangian have got nothing to do with it. Your error lies in your interpretation of the expression for kinetic energy. In fact you don't even need to involve kinetic energy. We only need to look at the particle velocity. The moment I see the ωXr expression, I can tell instantly that you have routed the velocity through a point on the rotating frame. ωXr is the tangential component of the particle velocity in the limit. And because it is in the limit, the other component must be radial. You cannot escape that fundamental reality which lies right at the heart of those transformation equations. What you did above was to cloud that reality up with a whole package of Hamiltonian, and integrals, and potential energies. David Tombe ( talk) 09:43, 7 May 2008 (UTC)
Timothy, the expression is absolutely dependent on it applying to the limit. If we consider the velocity vector split into two larger components, then none of those components are ωXr.
On Coriolis force, it is not involved in Lagrange points or stability because there is no curl in the gravitational field. And in your books, it cannot be involved in stability because it is only a fictitious force.
This is another example of your tactic which is to move the discussion into unnecessarily complicated zones such as Lagrangian, Hamiltonian, and the three body problem which has never been satisfactorily resolved. It is actually a deceptive tactic used by alot of people who have been proved wrong in the simple arena. Move the debate into the dark dirty jungles and cloud the whole issue. David Tombe ( talk) 11:46, 7 May 2008 (UTC)
Timothy, your six line proof fails on the first line before you even reach all the fancy Hamiltonians, integral signs, and potential energy terms.
Your proof fails at the point where you assume that if one component of the particle velocity is ωXr, that the other component has got arbitrary direction. The much more basic and less pretentious vector calculus that is used to derive the term ωXr insists that this term only applies when it is the tangential component of the particle velocity in the limit that this component tends to zero. It is the very same calculus that is involved in differentiating the position vector to obtain the general acceleration equation in radial/polar coordinates. We differentiate r and we end up with ωXr in the tangential direction and r dot in the radial direction. Your big problem is that when you were first shown the derivation of the rotating frame of reference equations, you never questioned that detail. You just accepted what you were told. Now that you have seen that there are restrictions of applicability which you had never thought about before, you are just digging in because you entered this argument without first checking your facts. Hence you are trying to cloud the whole issue by introducing high powered maths topics like Hamiltonians, and Lagrangians, and best of all, the ever controversial three body problem. None of these complications are necessary in order to analyse a simple vector triangle of velocity for a simple one particle motion with no potential energy terms. David Tombe ( talk) 15:58, 7 May 2008 (UTC)
Timothy, no you cannot. You are free to choose whatever value of velocity you like. But if one of its components is described by the expression ωXr, then it must necessarily be the tangential component, and therefore the other component must be the radial component. David Tombe ( talk) 06:34, 8 May 2008 (UTC)
Timothy, you can split the particle velocity into as many components as you like. But if one of those components is ωXr then the other component must be radial. This follows directly from the transport theorem. ωXr is the tangential component of the particle velocity in the limit. Hence the other component must be radial. You are ignoring a restriction that is built into the derivation. David Tombe ( talk) 10:09, 8 May 2008 (UTC)
No Timothy, it means that the equations only apply to particles that are co-rotating with the frame, because in those equations ω will represent both the angular velocity of the frame and the particle. If you choose ω not to be the angular velocity of the particle, then you cannot derive the transformation equations. There will be no physical linkage. v must be routed through the tangential term ωXr which is common to both the frame and the particle. 119.42.65.152 ( talk) 13:30, 8 May 2008 (UTC)
Timothy, let's see you deriving the transformation equations using a particle with an angualr velocity that is different from the angular velocity of the rotating frame? 119.42.68.141 ( talk) 10:14, 9 May 2008 (UTC)
, where .
Thus the position of the particle in the rotating frame is: . Hence
where we used that for any vector and in the last line that and Newton's second law in the inertial frame. The first statement is easy to check if done explicitly. The second statement basically is just line four of the argument. Here the derivation of the transformation formula if is not the angular velocity of . ( TimothyRias ( talk) 14:06, 13 May 2008 (UTC))
No Timothy, this is just another elaborate deception. The same vector triangle applies. You can't claim that the particle in question has a different angular velocity from the rotating frame simply by stating this to be the case before the derivation begins.
The derivation ensures that the angular velocity of the particle and the frame must be the same because as soon as we end up with one component of velocity given by rXω, then it must be tangential. And as such, the other component then has to be radial. 118.175.84.92 ( talk) 16:26, 13 May 2008 (UTC)
FyzixFighter, the orbital equation is found widely throughout applied maths textbooks. It takes the form,
-GM/r^2 + v^2/r = r double dot
It solves to give an ellipse, parabola, or hyperbola.
The inward -GM/r^2 term is the centripetal force. The outward v^2/r term is the centrifugal force. They both work together in the radial direction in tandem with each other.
I have been accused by two administrators of introducing unverified material by virtue of mentioning this information. That shows me that the editors that are dominating this page know very little about the subject matter. David Tombe ( talk) 08:01, 6 May 2008 (UTC)
FyzixFighter, Let's leave names and terminologies out of it altogether. We have a second order time differential for the radial distance from the focus. Call it acceleration if you like, or don't call it acceleration if you don't like. That second order differential term is equated to two other terms. One is an inward acting GM/r^2 term. Call it gravity if you like. Don't call it gravity if you don't like. We also have an outward acting v^2/r term. Call it whatever name you like. But one thing is sure. Both of these terms are very real. They are both radial, and they both act in opposition to each other. That's what planetary orbital theory is all about. It could be correctly said that one of these terms is the centripetal force and the other is the centrifugal force. That second order differential equation is difficult to solve, but it has been tackled over the last couple of hundred years by the top applied mathematicians and there are a number of ways of solving it. I have seen at least two methods. The one that I actually had to learn for my exams involved substitution and we ended up with a new variable U. The derivation went for at least a couple of pages. Maybe even three or four pages. The final result is the geometrical expression for a conic section. There will be two arbitrary constants in that expression. One is the semi latus rectum and the other is the eccentricity. When we know the initial speed, position, and direction, we can work out what these two constants are and that tells us the exact shape of the conic section. If the eccentricity is less than 1 we will have an ellipse. A circle is a special case of the ellipse. If we have an eccentricity that is equal to 1, we get a parabola. In other words, the object has escaped from closed orbit. If we get an eccentricity greater than 1, we will have a hyperbola. If you want to study this topic in more detail, I advise you to first of all brush up on the geometry of conic sections in polar coordinates. After that, you should find the orbital equation in any good undergraduate classical mechanics textbook. Goldstein probably has it. Here is another point of interest. There is a theorem which dircetly links Kepler's law of areal velocity to the tangential terms of the general acceleration vector which you quoted. That gets rid of both the Euler force and the Coriolis force. Gravity orbits are a zero curl affair. To have Coriolis force, we need a curl. But let's get back to the original point. Thanks to SCZenz's comments to the anonymous, I now know that my mathematical reasoning does not need any citations. For a circular motion to occur, the second time differential of the radial distance must equal zero. Hence the sum of v^2/r and the inward centripetal force must equal zero. In the artificial circle, which is purely an artifact and doesn't involve any centrifugal pressure at all, your team have been arguing that the outward centrifugal force v^2/r is counterbalanced by an inward acting Coriolis force. This is nonsense on a number of counts. The Coriolis force never acts radially. The Coriolis force and the centrifugal force are always mutually perpendicular. Do you remember the acceleration expression which results if we act directly on v? It is vXω. That is the parent force of both Coriolis and centrifugal before it gets expanded into two mutually perpendicular components. Also,even if your team are correct and we can make the Coriolis force act radially inwards, then the result will be twice that of the centrifugal force. So the second order time differential of the radial distance will not be zero. Hence we can't have a circular motion. Those transformation equations are only designed to deal with actual rotation. To invoke the Coriolis force we need a physical curl such as we get in hydrodynamics when an element of a rotating fluid moves radially inwards (or outwards) within itself. David Tombe ( talk) 04:55, 7 May 2008 (UTC)
Some remarks:
( TimothyRias ( talk) 09:09, 7 May 2008 (UTC))
The current introduction ends with the sentence, Colloquially, the term "centrifugal force" is sometimes also used to refer to any force pushing away from a center; this article discusses only the centrifugal force related to rotating reference frames. So where is the page on colloquial centrifugal force? That's the page the readers want. This sentence is effectively the same as saying, If you are looking for centrifugal force, you have come to the wrong page. David Tombe ( talk) 06:12, 7 May 2008 (UTC)
Probably everything to do with centrifugal force. David Tombe ( talk) 11:32, 7 May 2008 (UTC)
I want to see the peer reviewed proof that justifies the statements made in the main article. These need to be peer reviewed journal articles or reccomendations from a physics education committee and cited in the main page. As far I can determine, there is no peer reviewed, critically examined proof of what is said in the main article. Citations which refer to sources that repeat or draw conclusions from other unproved sources are not acceptable. I want to see the actual real proof, not hearsay that it exists in theory. 72.64.51.14 ( talk) 16:03, 7 May 2008 (UTC)
Thank you. As I understand it, you are officially stating that Wikipedia does not have a peer reviewed journal paper or physics education committe report to validate what you state in the main article. Therefore, I demand that you accept Mr Tombe's edits as valid edits, since you have failed to prove him to be wrong. He has produced textbook citations which back up his position, while you have produced nothing to validate your opinions. Evidently Wikipedia policy has failed in this case to produce the required proof to support the claims made in the main article. I insist that you correct the mistakes in this article, and allow Mr Tombe to make edits to this article. You have totally failed to prove him to be wrong and your actions and behavior are certainly objectionable in this matter, as you have behaved unfairly and rudely to him. You also need to correct these and apologise to him officially. 72.64.51.14 ( talk) 21:40, 7 May 2008 (UTC)
FyzixFighter, I refered you to Goldstein's Classical Mechanics. There, as well as in many other applied maths textbooks, you will see the orbital equation which I described to you above. That equations makes it clear that the second time derivative of radial distance is only zero when we have two opposing forces cancelling each other out, one of which takes the form v^2/r outwards.
Anome never demands citations from other peoples' edits. He only demands citations for my edits. And when I give citations, he ignores them and continues to demand citations.
When I give maths reasoning, I get the red card held up against me. When Timothy Rias gives maths reasoning, SCZenz comes in to say that it's all fine. David Tombe ( talk) 06:29, 8 May 2008 (UTC)
Thank you gentlemen. You have again failed to meet the minimum requirement of proof in science. That is a peer reviewed journal article that has been reviewed, discussed, debated, and validated. You have no physics education committe report that produces reccomendations, resulting from physics education studies, and justified by a peer reviewed journal paper that scientifically validates that what you write in the main article is correct. You are basically citing only opinion, and that opinion is not validated by any scientific procedure that I can determine. Therefore your main article claims are false and invalid and Mr Tombe has very right to dispute them and insist that they be changed. Your refusal to permit this is an injustice to him. Wikipipedia needs to correct this officially. I far as I can see Wikipedia policy has been officially used to abuse and insult Mr Tombe and that injustice needs to be corrected. Your failure to produce the required proof is a disgrace. 72.84.68.195 ( talk) 13:38, 8 May 2008 (UTC)
FyzixFighter, I don't think that Goldstein will overtly recognize centrifugal force either. It will adopt the same attitude as your book and work on the premises that gravity is the only force involved. But when the chips are down and the orbital equation appears, there will be two terms acting in opposition to each other in the radial direction. There will be a gravity term acting radially inwards and a term of the basic mathematical form v^2/r acting radially outwards. Whatever that v^2/r is, it is certainly not an artificial construct and it certainly doesn't arise because of any human desires as your book seems to suggest. It works in tandem (opposition) with gravity to produce conic section orbits.
A high quality textbook will generally remain silent on the issue of what this term actually is. It will be quietly borrowed from that general acceleration equation that we have been looking at. And as you must surely be aware, that general acceleration equation merely exposes inertia in the Cartesian frame to be the centrifugal force and the Coriolis force in a polar frame.
Yes, you are correct in that no modern textbook is likely to overtly declare the centrifugal term to be real. In fact, your book's declaration that it is artificial should surely alarm you. To claim such with regards to that scenario is the height of delusion.
Now I'd like to draw your attention to this line in your reference,
In order to reconcile this observation with the requirement that the net radial force vanish-that is, that the circular orbit be maintained
Now consider the artificial circular motion which is associated with viewing a stationary object from a rotating frame. How does it reconcile with this requirement? According to the 'Fictitious party' there is a radially outward centrifugal force and a radially inward Coriolis force that is twice as large. Yet if we are to have a circular orbit the centripetal force and the centrifugal force must be balanced.
The reality is that the equations for the coordinate frame transformation are only designed to cater for co-rotating objects. This condition is totally satisfied in meteorology.
Can you show me an explicit citation stating that these equations apply to objects that are stationary in the inertial frame. I wouldn't be entirely surprised if you could. But nevertheless, I would like to see it explicitly stated in a book. I have a feeling that the restriction to co-rotation has been overlooked by many people who have been introduced to these equations, and the error has been passed on from textbook writer to textbook writer.
Or perhaps the error isn't even in the textbooks and the mistake lies entirely with the readers. That's why I'd like you to find an explicit reference which overtly states that these equations apply to objects that are at rest in the inertial frame. David Tombe 119.42.65.152 ( talk) 16:11, 8 May 2008 (UTC)
Nobody ever mentions frames of reference when they describe the effects that take place due to centrifugal force inside a swerving car. They talk about these events as they stand in their kitchen, which is an inertial frame, and they state that as the car swerved around the corner, they got flung to the side door.
It is a matter of opinion which I don't subcribe to, to state that these events are more conveniently described from a rotating frame of reference. No such frame is needed in the description. When have you ever heard anybody going to the bother of explaining that as they viewed things from within the car, they were accelerated twoards the side door. The man standing watching it from the street saw exactly the same thing.
Such an argument however does not necessarily extent to the Coriolis force in relation to meteorology. 119.42.69.123 ( talk) 16:16, 7 May 2008 (UTC)
Wolfkeeper, the man in the street is quite capable of observing a radial acceleration towards the side door. We don't need to consider a rotating frame of reference to observe this. David Tombe ( talk) 06:23, 8 May 2008 (UTC)
Wolfkeeper, the man in the street sees the man inside the car getting flung to the side door. David Tombe ( talk) 09:55, 8 May 2008 (UTC)
Wolfkeeper, the man in the car is co-rotating. The back of his seat pushes him tangentially. This induces a vXω force radially. If he wasn't co-rotating with the car, he wouldn't be in the car, and he wouldn't be experiencing any outward tangential force.
And yes, this radially outward acceleration translates into straight line motion in the Cartesian frame. Centrifugal force in the polar frame is the same thing as inertia in the Cartesian frame.
Look at the conversion equation. Then remove the tangential components because of Kepler's law of areal velocity. Centrifugal force stands out as an inbuilt feature of straight line motion. David Tombe 119.42.65.152 ( talk) 16:32, 8 May 2008 (UTC)
Hi everyone. I understand that there are already textbook references that support the current version of the article straight down the line. However, it would be helpful if users would add in-line citations to sections that are being "warred" over. Talk page discussion is not settling this "argument"; I think administrative action will, but the case for administrative action is far stronger if directly-cited statements are being removed. I am willing to use my knowledge of physics to evaluate whether a source actually supports a statement, but not to treat a statement as cited just because I personally know it's correct and that it could be. So if instead of just reverting, you would consider in-line citations for the statements you re-add, it would save us all time in the end! -- SCZenz ( talk) 07:30, 8 May 2008 (UTC)
I notice that Timothy Rias has responded to this message by filling up the introduction with references for matters which are not in dispute. That is a bad sign. It shows that he has lost sight of the higher picture. David Tombe ( talk) 10:32, 8 May 2008 (UTC)
In reply to the above statement. I can provide just as many textbook references that contradict what is stated in the main article. Therefore I must conclude, that since I have just as many references that contradict what you say, then what you say is not justified by your selection of certain references that agree with what you beleive. That is not science. So you need to prove what you say is true, and you have not done it. 72.84.68.195 ( talk) 14:25, 8 May 2008 (UTC)
Wolfkeeper, I am fully aware of the fact that the Coriolis force doesn't involve any change in kinetic energy. But the Coriolis force does not occur in a zero curl field. There is no vorticity in the gravitational field that could invoke the Coriolis force. Kepler's law of areal velocity eliminates the Coriolis force from gravitational problems.
There is however Coriolis force in hydrodynamics because there can be vorticity. The ω is to all intents and purposes the vorticity. David Tombe ( talk) 10:24, 8 May 2008 (UTC)
Whether or not the curl of vXω is equal to zero is irrelevant. Kepler's laws eliminate the Coriolis force from all planetary orbital theory. 119.42.68.141 ( talk) 10:11, 9 May 2008 (UTC)
I have just blocked David for 31 hours for reinsertion of the same unreferenced assertions as before (see this diff), in spite of extensive warnings regarding the need to adhere to Wikipedia's polices. David, you are welcome to edit again when the block expires, but please try to edit according the WP:V and WP:NOR policies; that is to say, please provide verifiable cites to third-party reliable sources that back up your assertions. -- The Anome ( talk) 11:00, 8 May 2008 (UTC)
Sir, Again you have created an injustice with respect to Mr Tombe. As stated above, what you state in the main article is false, and Mr Tombe has every right to dispute it. Your policy is a disgrace as I stated above. You need to correct your behavior in this matter. Mr Tombe has clearly stated his sources on this talk page and you have none to prove him wrong. You need to produce the proof and you have not produced it. 72.84.68.195 ( talk) 13:54, 8 May 2008 (UTC)
The article cites five independent sources for the consensus content:
URLs and page references are provided in the article itself.
I'm sure the credentials of Stephen T. Thornton & Jerry B. Marion can be tracked down with similar ease, but I don't have the time to do so right now.
In each case, each work has a publisher that is independent of its author. The combination of all of these sources more than suffices to comply with the Wikipedia:Verifiability policy, as well as WP:NOR and WP:NPOV, which is all that is required here.
-- The Anome ( talk) 22:58, 8 May 2008 (UTC) [updated with more details 23:45, 8 May 2008 (UTC)]
Perhaps the discussion at Taylor, p. 358, which seems to cover many of the points raised, and can be viewed at Google books, would help to settle the disputes. Brews ohare ( talk) 19:56, 8 May 2008 (UTC)
There are clearly at least three interpretations of the term "Centrifugal force"
I think most people here will agree that the most common interpretation of the term "Centrifugal force" is the pseudo force. The question is, how important are the other two interpretations? I'm beginning to think that maybe giving the second one its own article is undue weight when in fact it is just a small minority that uses it in that precise sense. Note that the second interpretation is a subset of the third, so in most cases you can't tell from a quote that it only implies the second meaning and not the third. There are some cases where it would clearly be strange to use the term as in the second interpretation. For example, consider a binary star. For star A, the gravity from star B provides a centripetal force. Consequently, the gravitational pull on star B from star A would be the "reactive centrifugal force" even though it is not acting away from the center of rotation.
My conclusion is that both interpretations 2 and 3 are significant enough to warrant inclusion in this article, perhaps in an "etymology" section, but neither is important enough to have its own article. -- PeR ( talk) 21:00, 8 May 2008 (UTC)
I've just been scouting around for some more citable references.
Here's a peer-reviewed paper that describes centrifugal force as fictitious, for those that insist that only peer-reviewed sources are valid: Merab Gogberashvili, Coriolis Force and Sagnac Effect, Found.Phys.Lett. 15 (2002) 487-493. Quote: "In the rotating frame two fictitious gravity-like forces appear, namely the centrifugal and Coriolis forces. This is an illustration of the equivalence principle, which asserts that gravity and the accelerated motion are locally indistinguishable."
And for those who like citation by independent third-party reviews of the field, and/or appeals to authority: Richard Feynman, quoted in The Natural Philosophy of Leibniz by Kathleen Okruhlik, James Robert Brown (Springer, 1985, ISBN 9027721459, page 138) as saying (referring to rotation and centrifugal force) "These forces are due merely to the fact that the observer does not have Newton's coordinate system, which is the simplest coordinate system." -- The Anome ( talk) 00:40, 9 May 2008 (UTC)
Anome has totally misrepresented what the edit war is about. He has presented this war as being over the issue of whether or not centrifugal force is real.
The war is not about whether or not centrifugal force is real, although that did become a side issue when Anome opened up a special section entitled 'Is the centrifugal force real?'.
The war is not about whether the term fictitious force is applied to centrifugal force in the textbooks. We all know that it is.
The war is about the fact that all attempts to mention the cause of centrifugal force get instantly erased from the article. That cause is rotation. And we don't need any citations to back up that assertion because it is a well known and undisputed fact. 58.147.58.54 ( talk) 06:19, 9 May 2008 (UTC)
129.194.8.73, Does a centrifuge work if it is not rotating? 119.42.68.141 ( talk) 10:05, 9 May 2008 (UTC)
Anome, absolute nonsense. I'll ask you one single question,
Does a centrifuge work if it is not rotating?
The answer is 'no'.
Nowhere in the whole article does it say that the real effects of centrifugal force arise due to actual rotation. I tried to insert it yesterday and you blocked me and reverted the clause.
That was a very bad management decision and it was done on a false pretext. It had got absoloutely nothing to do with references, and besides that, I did give a reference to the wikipedia page on the Bucket argument which illustrated the point that co-rotation situations give actual effects whereas observing a stationary object from a rotating frame yields no effects.
You are pandering to a group such as the anonymous 129.194.8.73 above who are clearly not living in the real world. His mind is focused entirely on how a stationary object appears from a rotating frame of reference. And he deduces from that, that because the effect is artificial, that then it must be artificial for all cases including the centrifuge.
And you know that the effect is not artificial in a centrifuge. And you know that the centrifuge effect only occurs when the centrifuge is rotating.
So you blocked me on totally false grounds. It had got nothing to do with citations. The wikipedia rules clearly state that no citations are needed for obvious facts. And it is obvious that a centrifuge only works when it is rotating.
As for PeR's whinning about me evading the block, I never went unto the main article. How am I supposed to answer a hail of questions coming at me on the talk pages if I'm blocked from editing? PeR is actually the root cause of this entire problem because he is the arch-fictitiousist who is desperate to conceal the cause and effect aspect of centrifugal force. David Tombe 119.42.68.141 ( talk) 12:17, 9 May 2008 (UTC)
David: Everybody will agree that the centrifuge has to rotate. But the point is "How do you describe what is happening?" You have two choices to describe the rotating centrifuge: 1) Sit in the lab frame: the stuff in the test tube tries to stay still while the tube rotates. Relative to the moving tube, the stuff moves. 2) Sit on the centrifuge: the tube isn't moving, but the mysterious fictitious forces push the stuff down the tube. Brews ohare ( talk) 13:34, 9 May 2008 (UTC)
Brews, et al: I think it's become clear that it's a waste of time trying to explain the subject to David (unfortunate as that is). I've given up trying. On the positive side, all this has resulted in a lot of group effort to make the articles clearer and better referenced. Silver lining, eh ? Plvekamp ( talk) 13:45, 9 May 2008 (UTC)
"A centrifuge is a device consisting of a rotating container in which substances with different densities are separated by centrifugal forces on the substances." "This force is opposed by the frictional force of the fluid on the particle." Page 123 The Encyclopedia Of Physics, R. M. Besancon. This source says basically what Mr Tombe has been saying in his edits which you removed and eventually blocked. Since there is now a valid citation supporting Mr Tombe's claims, you need to remove your blocks and apologise to Mr Tombe. 72.64.55.233 ( talk) 13:50, 9 May 2008 (UTC)
In the section "is centrifugal force real" the following appears
Despite the name, fictitious forces are experienced as very real by anyone whose immediate environment is a non-inertial frame. Even for observers in an inertial frame, fictitious forces provide a natural way to discuss dynamics within rotating environments such as planets, centrifuges, carousels, turning cars, and spinning buckets.
To this sentence I propose adding:
For example, a description of the centrifuge from this viewpoint is: "A centrifuge is a device consisting of a rotating container in which substances with different densities are separated by centrifugal forces on the substances.…This force is opposed by the frictional force of the fluid on the particle." [1] See, for example, the article Lamm equation.
Any objections or modifications to this addition? Brews ohare ( talk) 15:16, 9 May 2008 (UTC) I implemented this change. Brews ohare ( talk) 19:44, 9 May 2008 (UTC)
All this rotation business makes things unnecessarily complicated when one wants to understand why the rotating bucket has hydrostatic pressure that the non-rotating bucket doesn't. There is an equivalent, much simpler experiment that only requires one to think in one dimension. Imagine that you have a friend sitting with his bucket of water in his spaceship, which is "standing still" (in an inertial frame of reference). You are in your own spaceship, with your own bucket, and your spaceship is accelerating away from your friend's. From your ship's frame of reference, you don't seem to be moving, yet your friend seems to be accelerating away from you. You explain his acceleration by means of a fictitious force that acts on your friend's spaceship. This fictitious force only exists in your frame of reference. Yet, your bucket will have weight, pressure and all that, while your friend's bucket will be floating freely inside his ship. This just goes to show the difference between inertial and non-inertial frames of reference, and that real forces (of the sort that make your bucket have weight and hydrostatic pressure) only relate to acceleration with respect to the inertial frame.
I have to agree with the majority that centrifugal force is a fictitious force and that the hydrostatic pressure in the rotating bucket is due to inertia (or acceleration with respect to an inertial frame of reference), same as the hydrostatic pressure in the bucket inside the accelerating spaceship. Didn't Einstein say that force due to acceleration was indistinguishable from gravity, by the way? -- Itub ( talk) 15:52, 9 May 2008 (UTC)
Sir you must surely be as confused as those with whom you profess to be in agreement. It seems all of you have become deranged. In your thought experiment, which is basically just a fictitious situation which does not really exist and can not exist, you suppose that because your spaceship is accelerating, but you dont know that fact, that it is reasonable for you to suppose that there is some fictitious force acting to explain that the other spaceship is accelerating. That is certainly a curious state of affairs. What your fictitious example shows is that if you are ignorant of your physical state you are certainly entitled to make false conclusions regarding the actual state of affairs about which you are ignorant. But of course, your reasonable false conclusion results from the fact that you don't have accurate knowledge of your physical state. Hence the hypothesis of a fictitious force arises from ignorance of the actual state of affairs and not from any valid concept of physics. 71.251.176.68 ( talk) 20:36, 10 May 2008 (UTC)
Can an example be provided to show what this statement means? For example, a book on a table exerts a gravitational force on the table that certainly results in a Newton's third law reaction by the table. This statement either should be supported by a clarifying example, or removed. What does it mean? In this connection, notice that the centrifugal force often is referred to as "artificial gravity" e.g. for astronaut training. See also Taylor. Likewise the statement that "they cannot be felt by a person subject to them" seems far-fetched. See also the point of view in Sedimentation. Brews ohare ( talk) 19:20, 9 May 2008 (UTC)
I think one way to resolve the difficulties regarding whether the rotating frame is 'fictitious' or not, is to use the equivalence principal - i.e., the physical phenomena are the same regardless of the coordinate system used. Any reference frame is as good as another; but the coordinates you use will depend on the choice. The simplest is an inertial, Cartesian reference frame in which straight-line uniform motion (no force) involves no 'fictitious' forces. Any other reference frame (accelerating, rotating, even polar) will include 'fictitious' terms due solely to a change of coordinates.
Another way to resolve it is to use coordinate-free vector notation, but to do any practical work we need to introduce coordinates.
There's a slightly subtle point about polar coordinates - Even in an inertial frame, motion will involve 'fictitious' terms due to coordinate transformation. Try describing straight line force-free motion in polar coordinates, you'll see what I'm talking about. Some of the arguments about inertial frames miss that point. Since we nearly always analyze orbital mechanics using polar coordinates, centrifugal and coriolis terms arise. One of David's examples above included the centrifugal term in orbital mechanics and he tried to say the force was 'real.' Nobody called him on it, and I think perhaps it was because we're so stuck on rotating frames in this article that the point was missed. Plvekamp ( talk) 15:14, 10 May 2008 (UTC)
Mr Plvekamp, it apears you are confused. Feynman clearly states that it does matter which coordinate system that you use. He states that the pseudo forces "are due merely to the fact that the observer does not have Newton's coordinate syatem, which is the simplest coordinate system." page 12-11, Vol 1 of his Lectures. Your statement that one reference frame is as good as another evidently indicates you dont understand this topic. I suggest that you do go back and check up on your memory and stop pulling facts out of the air. 71.251.176.68 ( talk) 20:07, 10 May 2008 (UTC)
I'm not disagreeing with Feynman; on the contrary, I completely agree that the appearance of pseudoforces depends completely on the coordinate system. What I'm trying to say is that a rotating frame is not the only way you'll see them; you'll also see them if you use polar coordinates in a stationary frame - check the reference I linked to [6]. I provided it to show that I'm not "pulling facts out of the air." The introduction as it stands seems to concentrate solely on rotating frames.
My statement that one reference frame is as good as another was in reference to the Equivalence Principle. In other words, a change in coordinate systems does not change physical law. You may have misunderstood me, in which case I apologize for not explaining myself well.
In any case, I won't make any changes to the article unless there is consensus (unlike another recently). Plvekamp ( talk) 20:52, 10 May 2008 (UTC)
Brews, There are a number of points to clear up.
(1) The edit war has been principally about the fact that these people here have been trying to deny that a centrifuge works BECAUSE it is rotating. They have been arguing that centrifugal force occurs when we view something from a rotating frame of reference. The two concepts are quite diffent.
I have been trying to insert the cause and effect aspect into the main article, but it gets deleted instantly every time.
These people think that a rotating centrifuge is equivalent to observing a stationary centrifuge from a rotating frame whose axis is on the axis of the centrifuge.
Clearly you can see that this is nonsense. A centrifuge will not be made to work in that manner. There is no equivalence principle involved in all of this.
However, there is a group here that are trying to promote the equivalence principle, and they are quite wrong. They are denying the age old Bucket argument.
(2) Orbital theory. Polar coordinates show up both the centrifugal force and the Coriolis force. However, Kepler's law of areal velocity eliminates the Coriolis force term. No Coriolis force is involved in the gravitational field.
We are then left with a radially inward gravity force and a radially outward centrifugal force which is absolutely real.
(3)Action - Reaction. In the real scenario, when actual rotation occurs, we get a radial centrifugal force, which as regards the issue of action-reaction, behaves exactly like gravity. However in the purely fictitious situation in which we observe a stationary object from a rotating frame, any effects are only fictitious and Newton's third law will be totally irrelevant. The group that are controlling this article are focused exclusively on the latter scenario. David Tombe ( talk) 04:13, 11 May 2008 (UTC)
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Prof Kleitman's notes.
Brews ohare (
talk) 14:26, 11 May 2008 (UTC)Brews, I can assure you that it is not centripetal force. I have worked at great length with that derivation and done many calculations in orbital theory. The terms in that equation are centrifugal force, Coriolis force, and Euler force. That equation in its own right doesn't infer any kind of motion. However when we apply Kepler's law of areal velocity to the gravitational field, the two tangential terms vanish. That leaves us with the radial terms. The radial terms, in the absence of gravity expose the fact that inertia is centrifugal force.
Brews, the maths in both of those articles is perfectly correct and I am well familiar with it. In fact it is basically the same maths in both cases. But you must never lose sight of the physical meaning behind the maths symbols. Those equations tell us alot. But they don't tell us everything. We need to model a real physical situation before we can decide how those terms fit in, and what they mean in any given context.
I took the gravity orbit as being the most well known physical context in which those equations are applied. Kepler's law of areal velocity is highly relevant because it gets rid of the two tangential terms. We are then left with a gravity force radially inwards and a centrifugal force radially outwards.
You have been trying to read a physical meaning into those equations in their own right. In their own right, all they do is convert polar coordinates to Cartesian. Centripetal force is not determined by those equations alone. We need to know the physical model before we can apply them and obtain a differential equation to solve.
Interestingly, they do tell us some information in their own right. If there was no applied centripetal force such as gravity or tension T in a string, or no applied torque, then in a space vortex, we would have a curved path caused by the centrifugal force and Coriolis force. If there were no vorticity, then the Coriolis force would disappear and we would be left with a centrifugal force acting alone. This would lead to a hyperbola with infinite eccentricity, which is essentially straight line motion. David Tombe ( talk) 09:34, 12 May 2008 (UTC)
Wolfkeeper, That's what is so interesting about Kepler's law of areal velocity. It means that there is no tangential acceleration. Of course we can still have a variable angular velocity.
Supposing we were to ignore Kepler's law of areal velocity. The polar coordinate conversion equations still wouldn't point us to any particular kind of motion. They would merely facilitate with the mathematical expressions that were needed in order to set up a differential equation modelling a real physical scenario.
Such a differential equation involving real tangential forces as well as real radial forces would almost certainly be non-analytical. David Tombe ( talk) 04:59, 12 May 2008 (UTC)
Wolfkeeper, I've lost track of the point that you are trying to make. I didn't bring the subject of polar coordinates up. But whoever did was correct to do so because it is relevant to the topic. David Tombe ( talk) 09:41, 12 May 2008 (UTC)
David, I just noticed your comment:
Are you saying the equivalence principle does not apply here? Can you provide a cite supporting this assertion, or is this your own original opinion? -- The Anome ( talk) 19:53, 11 May 2008 (UTC)
No Anome, this dispute has never been about cites. It has been about you and others falsely alleging that I have been adopting a fringe and unorthodox position.
I am waiting now for you to describe that position. David Tombe ( talk) 12:10, 12 May 2008 (UTC)
It appears that a digression is taking place to orbits and Kepler's laws of planetary motion. Is there a notion that something from those articles should appear here? Brews ohare ( talk) 05:16, 12 May 2008 (UTC)
Anome, a straight line motion across your kitchen does not involve any Coriolis force. It is ruled out by Kepler's law of areal velocity.
The effect that you have just described is a tangential artifact as viewed from a rotating frame of reference. The rotating frame of reference in this case is fixed in the rotating person. That is not Coriolis force. David Tombe ( talk) 12:07, 12 May 2008 (UTC)
No Anome, the radial effect can never be an artifact of circular motion. Only the tangential effect can be an artifact of circular motion.
You missed the point entirely. Centrifugal force in a zero-curl field is the same thing as inertia. There is centrifugal force built into every straight line motion. But there is no Coriolis force because Kepler's law of areal velocity eliminates it. We need hydrodynamics to get the Coriolis force. David Tombe ( talk) 12:34, 12 May 2008 (UTC)
Those derivations are correct, but they have got absolutely nothing to do with the point in question. The article is unlikely to be improved as long as SCZenz is involved in adjudicating. 118.175.84.92 ( talk) 16:44, 13 May 2008 (UTC)
FyzixFighter, I think we may now have identified the root cause of the edit war. You have just deleted my reference to the existence of two different kinds of scenario involving rotation.
(1) There is actual rotation. (2) And there is artificial rotation as when a stationary thing is observed from a rotating frame of reference.
Now I have been accused by Anome of adopting a minority or fringe viewpoint. Let's explore that so-called minority or fringe viewpoint.
My viewpoint, for which I will obtain cites if challenged, is that a centrifuge works BECAUSE it is rotating.
However, if we were to view a stationary centrifuge from a rotating frame centred on the centrifuge axis, the centrifuge would not work.
I do not believe that the "principle of equivalence" applies to rotation.
That is my viewpoint.
Is that a minority viewpoint? Do you think differently? Would you challenge it if I were to put that viewpoint into the main article? David Tombe ( talk) 09:48, 12 May 2008 (UTC)
Anome, in that case, if nobody is denying it, can you please tell me exactly what the edit war is about. And can you tell me why you erased an edit which I made to that extent and then blocked me from editing for 31 hours, extended by a further 25 hours on a petty technicality. You blocked me on the false pretext that I hadn't supplied a cite. But the rules say that a cite is only necessary if the clause is challenged. And even then, the correct procedure is to insert a 'citation needed' tag.
The edit that you erased and blocked me for is contained in this exert,
the centrifugal and Coriolis forces can have real physical effects in situations where the object in question is co-rotating such as in the case of the centrifuge device. In situations in which the object in question is not co-rotating, these fictitious forces are merely artifacts of coordinate transformation. The distinction between these two aspects of fictitious forces is the subject of a long standing debate known as the Bucket argument.Classifying such forces as "fictitious" reflects the special
Can you please point out exactly what aspect of this exert is being challenged, and why I had to be blocked for over two days for having made this edit. David Tombe ( talk) 12:28, 12 May 2008 (UTC)
Anome, coordinate frames have got nothing to do with it. It is the actual rotation that induces the centrifugal force. So if there is no co-rotation of the object in question, then there is no rotation.
The centrifuge illustrates quite clearly that centrifugal force only occurs when there is actual rotation.
So as regards your question, there would be centrifugal force based on the actual rotation of the object in question irrespective of what reference frame we viewed it from. In other words, there would be a centrifugal force associated with a 1Hz actual rotation. The frame that you mention rotating at 1.00000000001 Hz would have absolutely no bearing on the matter. David Tombe ( talk) 13:15, 12 May 2008 (UTC)
Anome, the two things in question for the purposes of co-rotation are the object in question that experiences the centrifugal force and the imaginary rotating frame of reference that you consider to be so important. If they are co-rotating, then there will be centrifugal force on the object as per the maths, and in a centrifuge that will cause a real effect.
If an object is not co-rotating with an imaginary rotating frame or even a real rotating frame, then nothing will happen to it. It will experience no real centrifugal force.
Does that point of view differ from the orthodox point of view? David Tombe ( talk) 14:11, 12 May 2008 (UTC)
It can't go to mediation until we've discovered what the dispute is about. The evidence is that a team of vandals and wikistalkers have been falsely alleging that I am adopting a minority and fringe position.
We need to await a declaration of exactly what that fringe position is. David Tombe ( talk) 12:37, 12 May 2008 (UTC)
Anome, you know the answer fine well and the answer is not being challenged. Hence no cites are necessary. A centrifuge has real effects and it only works when it is rotating.
Your deletions and blockings have got nothing to do with cites.
I think you are labouring this citations issue and hiding behind bureacratic slogans. David Tombe ( talk) 14:05, 12 May 2008 (UTC)
Anome, it says in the rules that cites are necessary when something is challenged. Are you challenging the idea that the real effects of a centrifuge only occur when the centrifuge is rotating?
Because if you are, I will get you a cite. If you are not, I will go ahead and put it in again without a cite. David Tombe ( talk) 14:24, 12 May 2008 (UTC)
OK RRacecarr, what was the problem with those edits? What would it be like for birds in an atmosphere in the absence of a gravitational field? David Tombe ( talk) 14:07, 12 May 2008 (UTC)
As long as the birds maintained a tangential path, things would seem normal. But they would have a hard job maintaining a tangential path as they got closer to the centre of the cylinder. So as they flew higher, they would begin to get disorientated.
There is also the issue of the fact that as they got closer to the center, the degree of co-rotation may reduce.This would effect the centrifugal force 118.175.84.92 ( talk) 16:52, 13 May 2008 (UTC)
David, you inserted the following text without a supporting citation:
This is [a] contrary to the predictions of the classical treatment of rotational motion (which is fully cited within the article), [b] uncited. You have persistently and consistently refused to provide cites, and this is just one more example. Accordingly, I am blocking you again. -- The Anome ( talk) 14:55, 12 May 2008 (UTC)
Go on then Anome, block it permanently and get it over with. I played by the rules. You didn't. All your blocks have been totally unlawful. That statement that I made above is perfectly true and it doesn't need any citations because it is not being challenged. It doesn't even relate to the controversy in question.
And your reversion of my reference to rotation yesterday was done under the totally false pretext of something to do with distance. 61.7.167.79 ( talk) 16:08, 13 May 2008 (UTC)
SCZenz, it's a pity that you don't know anywhere near as much about physics as you do about abuse of administrative authority. As long as you are around pushing your fictitiousist views and denying the cause and effect aspect of centrifugal force, this article will remain a mess. 118.175.84.92 ( talk) 16:31, 13 May 2008 (UTC)
Let me try to state David's viewpoint in words I understand, and without digressions in six different directions.
David agrees that observation of events from a rotating frame leads to a description using fictitious forces, including centrifugal and Coriolis forces. He also agrees that in an inertial frame the same observations do not require these forces. So far, everybody is on board.
However, David has reservations. Here are some possible interpretations of David's remarks:
Here is an alternative view of David's position:
If David can draw such conclusions from the article, perhaps so can other readers. A clear statement of these confusions and their resolution should appear in the article. Brews ohare ( talk) 15:19, 12 May 2008 (UTC)
Anome, your talking total nonsense now. Show us all a citation that states that the equivalence principle applies to rotation. As for Mach's principle, that disproves your position because it highlights the reality of the need for actual rotation in order to induce centrifugal force. 118.175.84.92 ( talk) 16:19, 13 May 2008 (UTC)
David seems to use a different definition of centrifugal force from the rest of us. In the interests of helping people communicate better, I thought I would try to state clearly what I think David means. Take the example of a particle in a centrifuge: David and everyone else agree that in the coordinate frame rotating with the centrifuge, there is a centrifugal force, determined by the rotation rate and the distance from the axis, acting on the particle. Where David's definition parts from everyone else's is in reference frames other than that particular one.
David's method: pick a reference frame rotating with the particle you're interested in, and calculate the centrifugal force. Then define that to be the centrifugal force no matter what reference frame you're in. In an inertial frame, or in one rotating twice as fast as the centrifuge, David's centrifugal force remains the same. Analysis in other frames would clearly require other fictitious forces in addition to David's centrifugal force, but he would argue that analyzing in any but the most "natural" rotating frame is an "ultra mathematical game"--the centrifugal force that the particle cares about, the one that it "sees", is the one in the reference frame rotating with it.
Standard method: pick any reference frame you want, and then define the centrifugal force relative to that frame. In the frame rotating with the centrifuge, the force is the same as David's. In the inertial frame, there is no centrifugal force. The force felt by the particle is applied by the wall of the centrifuge, and it accelerates inward in response. In the frame rotating twice as fast, the centrifugal force is twice as large as David's, but (in this special case) it is perfectly cancelled by the Coriolis force, and again the observed circular motion (in the opposite direction as in the inertial frame) is due 100% to the force applied by the wall.
Ok, maybe that will help people understand where David is coming from. Now maybe I can get David to consider whether the standard method actually might make sense to use in some situations (whether or not I succeed, the article will continue to exclude David's method until some references are produced, in accordance with WP:NOR).
As long as you are dealing with a single particle in circular motion at constant speed, David's method is fine. But what if the speed changes? With David's method, that requires a change of reference frame, which may not be convenient--angular acceleration of a reference frame introduces even more fictitious forces. Even worse, what if you have a bunch of particles, all moving around with different velocities within some rotating environment? David's method requires a different reference frame for each particle, to match with its actual instantaneous angular speed about the axis. In the standard method, all the particles are treated in the same reference frame, subject to the same (position dependent) centrifugal force. Differences in the velocities of the particles do result in differences in the fictitious forces they experience, but that is described by the Coriolis force, rather than by assigning each particle its own individual centrifugal force (which wouldn't, by the way, get rid of the need for a Coriolis force). Doesn't the standard way seem easier? Rracecarr ( talk) 15:57, 12 May 2008 (UTC)
RRacecarr, Let me now reply to your above assessment of my position. Your first part is more or less correct. We are all agreed that real outward radial effects occur when something is actually undergoing curved path motion.
In that case, why all the fuss? What is the fringe viewpoint that Anome keeps alleging that I am pushing?
And why are we not allowed to have any mention of this aspect of centrifugal force put in the main article?
I have tried on many occasions to highlight the fact that a centrifuge involves real radial effects which arise exclusively because the centrifuge is rotating. But these edits get swiftly removed every time. Itub and Timothy Rias have even tried to tell us that a centrifuge doesn't need to be rotating to work.
I was blocked from editing by Anome for inserting comments to the extent that a centrifuge does need to be rotating. And if you go to the notice boards behind the scenes, you will see that there is all sorts of panic going on and discussions about possibly blocking me permanently.
On your specific question, I would agree with you that rotating frames are useful in hydrodynamics, with meteorology being a classic example.
But not for a rotating snooker table. That never happens and it wouldn't work. There is no Coriolis force acting on free trajectories. You need to have actual curl as in hydrodynamics where the many particles are actually bonded to each other by inter atomic forces that are not subject to Kepler's law of areal velocity.
Anyway, I intend to re-insert the bit about the centrifuge into the section entitled 'Is the centrifugal force real?'. If Anome, or any of his colleagues in the administration, block me permanently on that basis, then we will all know the truth.
The truth is that there has been efforts made to play down the layman's concept of centrifugal force and to play up a fictitious aspect that is associated with artificial circular motion as viewed on stationary objects from a rotating frame of reference.
Have you got any citations regarding that theory about Coriolis force acting radially on a stationary particle when it is viewed from a rotating frame? There is a whole section on it in the main article and it seems to be given a much higher priority than anything to do with actual centrifugal force. David Tombe ( talk) 03:58, 16 May 2008 (UTC)
Itub, you said above, All this rotation business makes things unnecessarily complicated when one wants to understand why the rotating bucket has hydrostatic pressure that the non-rotating bucket doesn't.
The simple fact is that the hydrostatic pressure is induced because it is rotating. If we observe a non-rotating bucket from a rotating frame of reference, we do not get any hydrostatic pressure induced.
Hence there is no equivalence in the two situations. It is like the Faraday paradox.
So there are two distinct scenarios to be analyzed separately when answering the question 'Is centrifugal force real?'
And any attempts on my part to answer that question in relation to the actual rotation scenario are instantly erased, along with blocks and threats of permanent blocking. Such edits generate no end of panic on the notice boards behind the scenes.
So there is something seriously wrong going on. Some group here are totally intolerant of references to the real effects associated with actual rotation. David Tombe ( talk) 12:57, 16 May 2008 (UTC)
Anome, will a centrifuge work if it is not rotating? It's a yes or no answer. No need for all the hokum about reference frames.
David Tombe (
talk) 13:55, 16 May 2008 (UTC)
Yes. But he then tried to qualify it with a load of irrelevant hokum about frames of reference.
A centrifuge works BECAUSE it is rotating. End of story. There is nothing more to say on the matter. But this fact is not allowed in the main article and I was blocked for trying to put it in. So somebody has been abusing their administrative authority. David Tombe ( talk) 14:39, 16 May 2008 (UTC)
I'd like to request semi-protection for this article, and preferably for the talk page also. Both seem to be under attack from a POV-pushing anonymous from different IPs. Now there's nothing wrong with pushing POV, provided they include reliable refs, but this isn't.- ( User) WolfKeeper ( Talk) 03:53, 14 May 2008 (UTC)
p.s. I removed some anonymous comments from this page, it seems that they're David Tombe, and he's currently suspended, so that's vandalism in my book.- ( User) WolfKeeper ( Talk) 03:53, 14 May 2008 (UTC)
I've semi-protected the article; Tombe evidently is on a dynamic IP. I really don't want to protect the talk page, as then legitimate IP and new users are locked out of the article completely. In my opinion, feel free to just delete IP trolling on this talk page while he's blocked. We'll see what happens when the protection expires; may have to look into a range block, though i hate that too. Let's see how it goes. -- barneca ( talk) 04:22, 14 May 2008 (UTC)
This page is for discussing the article. Although the some of the discussions with David Tombe are related to the subject, I would really appreciate it if they could be kept on his talk page. One reason is I'd like to be up to date with the general discussion on this page, and it simply takes too long to read all the debates. Another reason is that he is currently blocked, and tempting him to answer via IPs is unfair, as that could have consequences for him. (He is allowed to edit his own talk page while blocked.) -- PeR ( talk) 15:12, 14 May 2008 (UTC)
P.S. I know I haven't always kept to this myself in the past. -- PeR ( talk)
In all the presentations of the fictitious forces, the Coriolis term and the centrifugal term appear with the same sign. Yet in the example in the section entitled "Fictitious Forces" claiming that a fictitious centripetal force acts on a stationary object as viewed from a rotating frame of reference, the two terms suddenly take on opposite signs.
Could we have a citation which explicitly states that the rotating frame of reference transformation equations apply to particles which don't themselves physically connect to the ω term.
It strikes me that someone somewhere has lost the connection between the maths symbols and the physical reality to which they are supposed to relate to. David Tombe ( talk) 13:30, 16 May 2008 (UTC)
Itub, can we please have the exact quote. David Tombe ( talk) 13:51, 16 May 2008 (UTC)
In other words Itub, there is no quote that backs up your point and the citation is bogus. David Tombe ( talk) 13:59, 16 May 2008 (UTC)
Anome, Page 233 wasn't available. We need to see an exact quote which explicitly states that the transformation equations apply to particles which don't themselves physically connect to the ω term.
The examples on page 234 relate to co-rotation so it doesn't look very promising. David Tombe ( talk) 14:16, 16 May 2008 (UTC)
There is no negative sign on your centrifugal force in the section in question in the main article. And your book doesn't say that those equations apply to particles that don't have the angular velocity ω. Where did that theory about the artificial circle come from? It's not in your book. David Tombe ( talk) 14:45, 16 May 2008 (UTC)
Now you are just talking nonsense. If the particle is stationary in the inertial frame, then it relates in no way to ω. The entire derivation of those equations was based on a particle whose tangential speed is related to ω. As for the signs, you have cooked the books in the main article by making the centrifugal force have a positive sign. David Tombe ( talk) 14:49, 16 May 2008 (UTC)
Do they have a "gun-boat diplomacy policy" too, to deal with administrators who engage in debates while continually threatening to permanently block those who they disagree with? David Tombe ( talk) 17:44, 16 May 2008 (UTC)
David: The Coriolis term depends on the velocity vector, so it flips sign if the velocity flips sign. If you look at Centrifugal_force#Examples you will see that the Coriolis force is opposite to the centrifugal force if the velocity has the appropriate direction. Brews ohare ( talk) 15:12, 16 May 2008 (UTC)
FyzixFighter, that was an interesting reference and it actually was relevant unlike the one supplied by Itub. It brought attention to the point that I have been driving at.
I have noticed that you in particular have been very interested in examining these effects starting with the coordinate-less velocity vector. We are agreed that this results in a vXω acceleration at right angles to the direction of motion and it is identical in principle to the qvXB force in electromagnetism.
This fact alone should direct you to the Faraday paradox and tell you clearly that the principle of equivalence does not apply to rotation.
Anyway, the expression vXω is the parent term for both the Coriolis force and the centrifugal force. Can you now see how Maxwell derived vXB from his sea of vortices? It's centrifugal force which he believed to be real and to be the cause of magnetic repulsion.
Anyway, those diagrams on P349 that you referred to correctly show that it doesn't matter what direction v is in to get the vXω deflection.
But I can assure you that if you split vXω into two mutually perpendicular components in polar coordinates, one being the Coriolis force and the other being the centrifugal force, then the Coriolis force will be the tangential component. The two can never act along the same line.
It was an interesting reference, but I want a reference which explicitly states that the transformation equations apply to particles that are not related to the ω vector, because the derivation explicitly requires that the particle in question possesses ω as its own angular velocity. David Tombe ( talk) 15:28, 16 May 2008 (UTC)
David. can you provide a reference that states that the transformation equation applies only to co-rotating objects? Also the reference in Marion&Thornton says (literally, I'm pretty sure, I'll check when I get home.) that if you modify Newton's second law by the terms in the transformation equation, that you get the EoM for a particle as described in a rotating frame. This means any particle including those that are not co-rotating. ( TimothyRias ( talk) 15:36, 16 May 2008 (UTC))
Brews, none of your examples involved the Coriolis force. The final example did involve a tangential deflection as viewed from the rotating frame, but that is not a Coriolis force.
Take a look at these two situations.
(a) Imagine a pole sticking up from the ground. An electrically charged projectile passes it at ten yards in straight line motion in the horizontal plane.
We will have the vXω (parent force for centrifugal and Coriolis) acting on the projectile due to its inertia. If the gravitational attraction of the pole is negligible, the straight line motion follows exactly as the solution to motion in a zero-curl field. Kepler's laws get rid of the Coriolis force and we are left exclusively with centrifugal force (inertia). The solution is a hyperbola of infinite eccentricity which is a straight line.
Now consider a particle at rest. Rotate the pole and nothing will happen.
(b) Consider the pole now to be a bar magnet with the magnetic axis along the length of the pole. This puts a curl into the field.
The Lorentz force is vXω (remember, Maxwell derived the Lorentz force with B being related to angular velocity).
This time the projectile describes a curved path due to the curl in the field.
However, rotate the pole on its magnetic axis and nothing happens.
The Faraday paradox and the Bucket argument are the same thing.
In your examples there is no curl and so there is no Coriolis force.
To get Coriolis force we need hydrodynamics. Maxwell showed that the magnetic field was hydrodynamics.
In meteorology, we get Coriolis force because elements of air move relative to the larger entrained body of rotating atmosphere. Kepler's laws don't apply on the inter molecular scale and we can see that the Coriolis force is a real effect simply by observing the spiral cyclones from space. David Tombe ( talk) 17:14, 16 May 2008 (UTC)
Hi David: Well, you haven't directly answered my question about the Dropping Ball example, although your statement "In your examples there is no curl and so there is no Coriolis force." seems to mean you disagree with it. I'd like to track down how we might differ on this example – that might help me to understand your viewpoint. To reprise the article's approach, the rotating observer sees the falling ball trace out a circular path. As with any student of mechanics, he concludes a centripetal force must be at work – otherwise the ball should follow a straight line, and obviously it does not do that. That is about as far as he gets with this problem. However, if he does a bit more study, looks at balls falling at different rates and radii, he will come up with an explanation based upon the forces F = –2mΩ × v – mΩ × ( Ω × r). Call them what you will, if these forces are put into Newton's laws the correct trajectories emerge. Where would you fault this process? Brews ohare ( talk) 18:03, 16 May 2008 (UTC)
{{
cite book}}
: |page=
has extra text (
help) and Vladimir Igorevich Arnolʹd (1989).
Mathematical Methods of Classical Mechanics. Berlin: Springer. p. §27 pp. 130 ff.
ISBN
0387968903.. They also are derived at
Fictitious_force#Rotating_coordinate_systems. Can we agree that these forces apply?
Brews ohare (
talk) 19:04, 16 May 2008 (UTC)Brews, OK, we'll start with that one. I was never denying that mathematical expression. I was saying that nobody as yet has provided a citation which explicitly states that the above equation can be applied to objects that do not physically possess the angular velocity ω. The derivation of that equation begins by considering a particle which possesses that angular velocity. David Tombe ( talk) 04:31, 17 May 2008 (UTC)
To quote from the article:
To answer this question, let the coordinate axis in B be represented by unit vectors uj with j any of { 1, 2, 3 } for the three coordinate axes. Then
The interpretation of this equation is that xB is the vector displacement of the particle as expressed in terms of the coordinates in frame B at time t. From frame A the particle is located at:
In this quotation frame A is inertial and frame B is accelerating. The derivation then carefully distinguishes between the motion of the particle and the change in the coordinates and unit vectors in the accelerating frame. The result is the equation for forces that is agreed upon. The definition of ω is as below:
If the rotation of frame B is represented by a vector Ω pointed along the axis of rotation with orientation given by the right-hand rule, and with magnitude given by
then the time derivative of any of the three unit vectors describing frame B is: [1] [2]
and
These unit vectors are attached to the rotating frame, not to the object under observation.
For Huygens and Newton centrifugal force was the result of a curvilinear motion of a body; hence it was located in nature, in the object of investigation. According to a more recent formulation of classical mechanics, centrifugal force depends on the choice of how phenomena can be conveniently represented. Hence it is not located in nature, but is the result of a choice by the observer. In the first case a mathematical formulation mirrors centrifugal force; in the second it creates it.
The primary aim of this paper is to show that in the eighteenth century centrifugal force was a problematic notion in many respects. Moreover, I intend to show that current views concerning the ideas on centrifugal force expressed by Newton in the Principia mathematica are severely affected by the projection of modern methods and ideas that are found neither in the Principia nor in works contemporary with it. I hope that my analysis will stimulate a fresh reflection on Newton's mechanics and its reception.
The Relativization of Centrifugal Force Author(s): Domenico Bertoloni Meli Source: Isis, Vol. 81, No. 1, (Mar., 1990), pp. 23-43 Published by: The University of Chicago Press on behalf of The History of Science Society.
David Tombe ( talk) 17:33, 16 May 2008 (UTC)
Anome, the point remains, can you tell me exactly what is the fringe point of view that you keep accusing me of trying to push?
Here in essence, as far as I can remember, was my introduction which started the war,
When an object undergoes curved path motion, it experiences a force directed away from the center of curvature. This force is known as the Centrifugal force (from Latin centrum "center" and fugere "to flee").
Centrifugal force should not be confused with the inward acting centripetal force which causes a moving object to follow a circular path.
In the days of Newton, Bernoulli, and Maxwell, centrifugal force was considered to be a real force, but the official position nowadays is that centrifugal force is only a fictitious force which acts in rotating frames of reference.
Where is the fringe viewpoint contained within this very basic and easy to read introduction? David Tombe ( talk) 18:22, 16 May 2008 (UTC)
Anome,
Here is a quote from Bernoulli out of the ET Whittaker book on the history of aethers.
"The elasticity which the Aether appears to possess, and in virtue of which it is able to transmit vibrations, is really due to the presence of these whirlpools; for, owing to centrifugal force, each whirlpool is continually striving to dilate, and so presses against the neighbouring whirlpools."
And here is a quote from Maxwell's paper 'On Physical Lines of Force' in relation to the mutual repulsion that occurs between adjacent magnetic field lines,
"The explanation which most readily occurs to the mind is that the excess of pressure in the equatorial direction arises from the centrifugal force of vortices or eddies in the medium having their axes in directions parallel to the lines of force"
When you first denied that these quotes indicate that Maxwell and Bernoulli believed centrifugal force to be real, you lost all credibility.
A few hours ago somebody put in a bogus citation in reply to a 'citation needed' request. When pressed to give the actual quote, they began to drag their feet. In the end, we saw that there was nothing in the citation that was relevant.
When I removed the citation, I got a warning in my tray from you not to remove valid citations.
This has been your characteristic gun-boat diplomacy style all along.
You are steering this article to support a fringe viewpoint which does not appear in any textbook, and to that end, you are abuisng your administrative powers.
The fringe theory in question was probably the original research of one of these wikipedia editors.
I will remove it now. Feel free to block me permanently if you so wish, but your intervention in this debate along with the behaviour of the others has turned the whole page into a circus. David Tombe ( talk) 04:47, 17 May 2008 (UTC)
Although I personally disagree with David Tombe on the points he has raised, response to his points has led to the tightening of the arguments in the articles and the addition of two figures, one in fictitious force and one in centrifugal force and a clarification of sentences and phrasing that make both articles much clearer. In my opinion, this improvement would not have occurred without David's input. Debate is useful, despite a tendency to boil over. Brews ohare ( talk) 16:56, 18 May 2008 (UTC)
We now have a fairly good, well referenced, account of the modern treatment of the concept of centrifugal force in classical mechanics. I'm sure it can be improved in the long term from a pedagogical viewpoint, but it's an excellent start. However, I think there are several ways in which this article could be improved further.
Firstly, it would be useful to have a section on the development of the concept of centrifugal force in the history and philosophy of science. For example, there appears to be some literature (see above) to suggest that the concept of centrifugal force held by Newton and Huygens differed somewhat from the modern concept.
Secondly, it would be useful to have a section on the everyday conceptualization of centrifugal force from the viewpoint of naive physics. There appears to be a fair amount of research on this, particularly from the viewpoint of research into science education, where it is a major stumbling block for students. There is also some research devoted to the concept as an example of metaphor formation in the artificial intelligence literature.
Thirdly, it would be interesting to have a section on how these problems are overcome in science education: there also appears to be some literature on this topic, including studies of the effectiveness of different approaches.
With these sections in place, based on reliable sources and cited to the same standards as the rest of the article, I think we would be in a good position to push towards featured article status.
Would anyone be interested in developing these topics further? -- The Anome ( talk) 10:35, 21 May 2008 (UTC)
One of three key objections to the extrapolation of the transformation equations to fictitious situations surrounds the issue of 'net radial force'.
These transformation equations are claimed to produce a net centripetal force on a particle that is at rest in the inertial frame but viewed from a rotating frame.
However, in circular motion, it is quite obvious that the net radial force is zero.
Consider the general equation for a central force orbit. It takes the form,
Applied Centripetal Force + Induced Centrifugal Force = Resultant Radial Force
This is the equation used for the gravity orbit.
We can also apply it to any orbital motion. Consider an object being swung around in a circle on the end of the string.
T for tension goes into the centripetal force slot. mv^2/r is the centrifugal force. The resultant radial force is zero and hence we end up with the equation,
T = mv^2/r
If we try to apply this equation to the artificial circle according to the theory being pushing by the fictitiousists, we will have a net centripetal force mv^2/r. The radial accleration is zero and so the equation will not be balanced.
SBharris and others seem to think that the net radial acceleration in circular motion is not in fact zero. They base this on the fact that the centripetal force has supplied an inward radial force which causes the particle to continually change its direction.
Of course such a force does exist and does produce that effect. But the net radial acceleration is still zero and so the only conclusion can be that there is also an outward centrifugal force. And this outward centrifugal force can be observed inducing Archimedes' principle in a centrifuge. It can be felt reacting against the centripetal force as like weight in the case of gravity. It can even be observed in straight line motion in the absence of any centripetal force. And most importantly of all it is used in the complex analysis of planetary orbital motion.
Consideration of the more general elliptical and hyperbolic situations makes centrifugal force an essential tool in the analysis. If we restrict our studies to circular motion where centripetal force, induced centrifugal force, and reactive centrifugal force are all equal then the induced centrifugal force becomes obscured.
Elliptical situations can be compared to weight variations in an accelerating elevator. The normal reaction and the weight change, but gravity doesn't. Likewise in elliptical motion, the induced centrifugal force (analgous to gravity) is not cancelled by the centripetal force (analgous to normal reaction) and hence the reactive centrifugal force (analgous to weight) is not generally equally to the induced centrifugal force. David Tombe ( talk) 07:26, 24 May 2008 (UTC)
We must distinguish between applied and induced effects. The transformation equations tell us no physics. They merely tell us the mathemtical form of a force that acts at right angles to a motion. They tell us nothing about the source of either a centrifugal force or a Coriolis force.
We need actual physical situations in which to apply these equations to.
One good example is a rotating turntable with a radial groove in which a marble can roll along freely.
This situation demonstrates induced centrifugal force as a real radial effect.
But there is no naturally occuring induced Coriolis force in curl-free space.
When the marble rolls out radially, it is constrained to a co-rotating radial path by an 'Applied Coriolis' force in the tangential direction. This applied Coriolis force is directly analgous to centripetal force.
The marble in turn will cause an equal and opposite tangential force on the turntable. This will be a "Reactive Coriolis Force" by analogy with reactive centrifugal force.
This article has totally played down "induced centrifugal force" and relegated it to "colloquial centrifugal force" and more recently to the classic newspeak terminology "Centrifugal Tendency".
Rotation as the cause of induced centrifugal force has been censored in the main article. David Tombe ( talk) 08:00, 24 May 2008 (UTC)
Brews, the point that I was making was that in the case of the marble rolling out the radial line, the Coriolis term in the above equaion applies and so does the centrifugal force term.
But the equation above doesn't tell us why they apply. We know that they apply simply by observing the scenario. We know that the centrifugal force is induced in the radial direction. We know that there is an applied and a reactive Coriolis force in the tangential direction. The equation on its own tells us absolutely nothing in the absence of a real physical scenario within which to apply it. David Tombe ( talk) 14:10, 24 May 2008 (UTC)
Brews, it's not even a transformation equation. It tells us nothing. It is modern physics gone mad. It gives us the mathematical form of the centrifugal force (and/or the centripetal force) and the Coriolis force and nothing more.
If you think that that equation contains real physics, then can you tell me exactly what trajecory it describes?
It's supposd to describe effects as viewed from a rotating frame. But it will only do that if those effects actually exist. David Tombe ( talk) 14:42, 24 May 2008 (UTC)
Brews, in the dropping ball example, all I can see is an artificial circular motion imposed upon the actual motion when it is viewed from the rotating frame.
I don't see either a centrifugal force or a Coriolis force at work. From the rotating frame of reference, we would need to see a tangential acceleration before we could start talking about Coriolis force. And we would need to see some radial acceleration before we could start talking about centrifugal force.
Those so-called transformation equations don't even describe the artificial circle.
The dropping ball is quite simply not a demonstration of either centrifugal force or Coriolis force.
I gave you the best demonstration. It is a marble rolling along a radial groove on a rotating turntable with a wall at the edge to hold it in.
That gives you everything,
(1) Induced centrifugal force
(2) Applied centripetal force
(3) Reactive centrifugal force
(4) Applied Coriolis force
(5) Reactive Coriolis force
The only thing it doesn't give you is induced Coriolis force and applied centrifugal force.
Induced Coriolis force is a tricky one, but applied centrifugal force would occur if an engine were to accelerate an object radially outwards along a groove on a rotating turntable. David Tombe ( talk) 16:38, 24 May 2008 (UTC)
No Itub, if the groove were curved, any radial force would be centripetal and centrifugal. Centrifugal force is a radial effect caused by actual tangential motion, no matter how we look at it. David Tombe ( talk) 09:56, 29 May 2008 (UTC)
In the inertial frame, the diplacement is
In the rotating frame the ball drops veritcally in the same way, but appears to rotate:
This equation is the displacement of the ball as recorded by the rotating observer in their reference system. In the rotating frame the unit vectors appear stationary, so their estimate of the acceleration is
that is, an inward centripetal force. Having no physical means of supplying this force. such as a tether or gravity, these observers resort to the fictitious forces of the article. When these fictitious forces are considered, the rotating observer agrees with the inertial observer that there is no real force on the ball, only the ubiquitous forces that they see everywhere, forces without apparent origin in gravity, electromagnetism etc.. Brews ohare ( talk) 17:21, 24 May 2008 (UTC)
David: I'll intersperse my comments among yours:
David: These remarks are incorrect. Circular motion when projected on an axis does become simple harmonic motion along the axis. That does not mean that circular motion IS simple harmonic motion. It means its PROJECTION is simple harmonic motion. Your remarks about radial acceleration have been dealt with completely and authoritatively by other commentators in earlier exchanges. Your idea here is plain and simply a misconception. Please re-read what has been said about this. For example, by SCZenz below. Brews ohare ( talk) 04:21, 27 May 2008 (UTC)
SCZenz, we are exclusively looking at the radial component of the acceleration. That is all that is involved in central force analysis. Any advanced classical mechanics textbook will confirm that fact.
The only equation which is relevant for this entire article is,
applied centripetal force + induced centrifugal force =
It is a second order differential equation and r is the variable. The centrifugal force is naturally induced by tangential motion and all we have to do is insert the applied centripetal force.
When we have circular motion, will be zero and hence the centripetal force will be cancelled by the centrifugal force.
That is all there is to it.
You can use that equation to analyze any central force situation.
But in your artificial circle example, you have a net inward centripetal force and so the equation is unbalanced. David Tombe ( talk) 07:45, 25 May 2008 (UTC)
SCZenz, have you never seen the orbital equation being solved in an applied maths textbook? That equation that I have cited is a scalar equation. We are only interested in the radial component of the acceleration and variations in the radial magnitude. David Tombe ( talk) 10:38, 26 May 2008 (UTC)
David: It is your reading of the math books that is faulty here. If you wish to challenge the orthodox treatment of the article, you'll have to get mathematical yourself. I'm of the opinion that you are completely wrong and what you claim cannot be proven. You'd be more useful as a contributor if you focussed on matters other than the rigor of the approach, which is in good shape as it is now. Brews ohare ( talk) 04:21, 27 May 2008 (UTC)
To proceed, the fictitious force is:
Vector Ω describes the rotation of the rotating frame. If they observe the ball to be moving counterclockwise, this rotation is clockwise so:
Hence, Ω × v is:
Consequently, the Coriolis force (related to -2 × the above) is inward radial with twice the value of the outward radial centrifugal force, leading to the rotating observer's requirement of an inward centripetal force, as calculated above. Brews ohare ( talk) 17:59, 24 May 2008 (UTC)
Hi David: I'll intersperse comments between yours:
I do not understand how the derivation is so restricted. Please spell out the mathematical assumptions that are the supposed source of such restriction. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
This is simply an assertion on your part with no support. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
Again, I fail to see any such restriction in the mathematics. Please point out mathematically where your viewpoint comes from. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
This notion is your own, and has no basis. Brews ohare ( talk) 04:07, 27 May 2008 (UTC)
Brews, it's not my own notion. In a gravity orbit, when there is circular motion, the radial acceleration absolutely has to be zero. See the new section below. David Tombe ( talk) 07:15, 27 May 2008 (UTC)
David: two problems as I see it. Problem 1 is that you are so far off the beam that it may well be impossible for you to understand the presented arguments at all. Problem 2 is that you are unwilling to adopt the perspective of the article and show how it runs amok. Instead you flail away at it from premises that are of your own invention, thereby completely disconnecting yourself from any viable conversation. I have taken the time to outline in mathematical detail the approach of the article (which is also the approach of all published articles on the subject that I have read to date, and certainly that of the most reputable ones). In contrast, you have not undertaken to go through this math and point out what you consider to be its deficiencies. I find that reluctance on your part to be a failure to engage in responsible argument. If you were to do that, I believe you would rapidly identify your mathematical errors and abandon your viewpoint. Brews ohare ( talk) 04:28, 27 May 2008 (UTC)
SBharris, the derivation of the transformation equations is essentially the same maths that is involved in polar coordinates. All we are doing is obtaining mathematical expressions in the radial and tangential directions for a force that acts at right angles to a motion.
The Coriolis force term is unequivocally a tangential term.
Whoever was first to apply that Coriolis term to radial motion made a big mistake and it doesn't surprise me at all if Feynman fell for it too, or for all I know maybe even originated it.
On radial motion there is only one important equation. It is,
Applied centripetal force + induced centrifugal force =
Hence if we have a circular motion, then will necessarily be zero and the centrifugal force will be exactly balancing the centripetal force.
It has got nothing to to with frames of reference. We can see radial motion in a system perfectly well without having to rotate with that system.
Your big problem is that just because you have seen that a centripetal force is acting radially inwards, you then assume that there must be a net radially inward acceleration. Yet it is obvious that there isn't.
So you look at = zero yet still claim that there is a net radial acceleration. This is because you don't want to involve the centrifugal force which is a critical aspect of the entire central force analysis.
And now having realized that since gravity and centrifugal force are both radial and that hence if one is real, the other must also be real, you have decided to opt for the ludicrous conclusion that they are both fictitious. David Tombe ( talk) 08:21, 25 May 2008 (UTC)
The orbital equation,
Applied centripetal force + induced centrifugal force =
is a scalar equation. The only variable is the radial distance. It is solved as a scalar equation in standard university applied maths textbooks such as Goldstein's.
If you would only apply that equation to any non-circular scenario, then all your problems regarding centripetal force, reactive centrifugal force and induced centrifugal force would be explained. But by confining your studies to circular motion, the ensuing equality of the three blurs the distinction between them.
On another matter, there are only two directions in space. There is radial and tangential. That is clear on both the microscopic and the cosmological scales. Cartesian coordinates and Newton's law of inertia are only good in the limited close-up context as like inside a cuboid kitchen where hyperbolic motion appears like straight line motion.
And because of Kepler's law of areal velocity, there is no naturally occuring Coriolis force and we don't need to do a full vector analysis of the problem.
And it's a pity that Itub doesn't pay as much attention to what Maxwell says as he does to what Feynman says. Feynman contributed nothing towards either classical mechanics or classical electromagnetism. You'll have to learn to move out of that 'Feynman worship' attitude whereby scientific progress ends forever at the mistakes that Feynman didn't spot. David Tombe ( talk) 10:08, 26 May 2008 (UTC)
I've now started a section on the historical development of the modern conception of centrifugal force in this article. I am by no means an expert in the history of science, and I'm unsure about how the references I've cited hold together: could an expert please review the material I have added so far? There appears to be significant work on this topic by Domenico Bertoloni Meli (for example, [12], [13]), however, most of the interesting papers on this subject are behind a paywall and inaccessible to me. -- The Anome ( talk) 12:23, 25 May 2008 (UTC)
SBharris, even engineers know that a component of a vector is a scalar, and that the central force equation is a scalar equation in radial distance. Are you denying this scalar equation which is in all texbooks about orbital theory,
Applied centripetal force + induced centrifugal force =
We are only concerned with the radial direction. You have consistently reminded us all that the centripetal force acts radially inwards and that it changes the direction of the particle even when the tangential speed remains constant. You seem to think that you are educating people that don't know the difference between speed and velocity.
But you are the one who has failed to tell us all why it follows that, if there is an inward radial centripetal acceleraion, that there must be a NET inward radial acceleration. In circular motion, there clearly isn't a net inward radial acceleration because has to be zero.
Are you denying the above equation? David Tombe ( talk) 06:25, 27 May 2008 (UTC)
SBharris, that is the exact equation which is used in advanced classical mechanics textbooks. It is a scalar equation and the variable is the radial distance. There is no tangential acceleration involved in any of the problems that we have been discussing. In a circular orbit, we have an inward radial centripetal force balanced by an outward radial centrifugal force and hence will be zero.
It is now clear that you are stuck in the limited high school mode where they emphasized only a part of the overall picture. They emphasized the fact that velocity has both magnitude and direction and that a centripetal force changes the direction of the particle while leaving the speed unchanged (in cases of uniform circular motion).
You have not moved on from that. I have taught that myself. But I am showing you the equation that is used in planetary orbital theory. It is in the advanced textbooks and you are simply denying it. It shows clearly that must be zero in a circular orbit. However in your artifact circle, this equation is not balanced because the application of the transformation equations to that scenario is a nonsense. David Tombe ( talk) 10:50, 27 May 2008 (UTC)
Wolfkeeper, You said above that,
I got two self-evident accelerations, a radial one outwards and the coriolis that always curved the velocity in the opposite direction to the frame rotation.
The centrifugal force will have been real and dependent on the exact angular velocity of the particle in question.
Regarding your observed Coriolis artifact, did it ever act in any direction other than the tangential direction? David Tombe ( talk) 10:16, 26 May 2008 (UTC)
Wolfkeeper, a purely tangential motion will never go inside the circle. If you see anything going inside the circle, it means that there was a radial motion to begin with.
Once again, you are too focused on artifacts to actually see what centrifugal force really is. David Tombe ( talk) 06:58, 27 May 2008 (UTC)
Wolfkeeper, well at least you are now admitting that the centrifugal force only acts on co-rotating objects (although it's not quite as simple as that). The Coriolis force on a roundabout will be an applied force which acts tangentially on co-rotating radial motion and it is likely to trip a walker up if he decides to walk a radial line on a roundabout.
No tangential motion on the roundabout can possibly cause a deflection to act such as to move the object inside the circle of which it forms a tangent. David Tombe ( talk) 11:10, 27 May 2008 (UTC)
We need to get to the point here. Is everybody denying this scalar equation,
Applied centripetal force + induced centrifugal force =
It's a second order differential equation in radial distance and it is used to solve planetary orbital problems. It can also be used for any central force scenario.
Are you all denying this equation? It is found in any advanced classical mechanics textbook.
It contains one out of at least four reasons why the artificial circle idea is nonsense.
I have been accused of not having pointed out the maths errors in the transformation equations despite having done so on numerous occasions. The equation above relates to a very important one of those maths errors.
So do you all accept this equation or not? David Tombe ( talk) 06:54, 27 May 2008 (UTC)
TstoneT, I'm not sure what you mean about stationary polar coordinates. Does that mean no tangential motion? We need the tangential motion to induce radially outward centrifugal force. Stationary polar coordinates would only be useful if we were focusing exclusively on gravity problems where things fell straight downwards. David Tombe ( talk) 07:23, 29 May 2008 (UTC)
Itub, in your artificial circle example, you also use the radial direction and that's what we're comparing it with. No need to play the old trick of hiding behind Cartesian coordinates.
Your so called centripetal force that derives from the Coriolis force is in the radial direction. At least that is what you have been trying to argue, so you can't have it both ways. In your artificial circle example you have a net inward radial force. That is impossible in circular motion. In circular motion is zero because the centrifugal force balances the centripetal force in the radial direction. Your artificial circle example causes a total imbalance in the central force orbit equation. David Tombe ( talk) 10:58, 27 May 2008 (UTC)
No Itub, the entire transformation theory which you are basing it all on is done in polar coordinates and your Coriolis force supposedly swings into the radial direction. You have a net radial force for a circular motion and so your theory is a nonsense.
You cannot keep jumping out of polar coordinates when it suits you. David Tombe ( talk) 11:19, 27 May 2008 (UTC)
Example: | Inertial frame viewpoint | Rotating frame viewpoint |
---|---|---|
"Real rotation" |
|
|
"Artificial circle" |
|
|
Anome, it doesn't at all surprise me that you agree with Itub. But your boxes above completely ignore the fact that if centrifugal force and centripetal force both act in the radial direction, then we either have them both or we have neither. In your first box you acknowledge radially inward centripetal force while denying radial outward centrifugal force even though we know that in circular motion, must be zero.
And it is that latter fact which is the key point in the dispute. Your boxes are just sheer obfuscation. In the artificial circle, the radial length remains constant, hence must equal zero. But in your theory, you are ascribing to it a net inward radial force.
On the issue of consistency, I am the one that has been totally consistent. I talk only about the radial dircection. You are the ones that keep jumping between Cartesian and polar coordinates like stage magicians, and switching off centrifugal force when you think that nobody has noticed. David Tombe ( talk) 03:04, 28 May 2008 (UTC)
FyzixFighter, you are telling me something that I already know. I know all about polar coordinates and their derivation. But when we get to central force problems, it all reduces to a scalar equation in the radial length.
is to all intents and purposes the radial acceleration in the context. If you don't want to call it that, then so be it. But the physical realities will not change.
The term has to be zero for a circular motion. Hence, the artificial circle example fails because it talks about a net centripetal acceleration in the radial direction. In a proper circular motion, the centrifugal force and the centripetal force will cancel and will be zero. David Tombe ( talk) 07:12, 29 May 2008 (UTC)
Here's a quote from the wikipedia verifiability policy,
Editors should provide a reliable source for quotations and for any material that is challenged or is likely to be challenged, or the material may be removed.
Let's see if the administrators abide by the rules or not. I have added into the introduction that centrifugal force in the so-called colloquial sense (not my choice of terminology) occurs in connection with rotation.
Is anybody challenging this fact? If so can they give me an example of colloquial centrifugal force that is not connected with rotation?
If my insertion is deleted, it proves that you are merely throwing pies, and that you are not in the least interested in centrifugal force. David Tombe ( talk) —Preceding comment was added at 07:23, 27 May 2008 (UTC)
No Anome, the article is about centrifugal force in physics not in politics. Are you being serious, or are you just being silly? David Tombe ( talk) 10:52, 27 May 2008 (UTC)
Well now you've got Wolfkeeper claiming that the articles are on topics and not terms. I suggest we remove the reference to political centrifugal force. David Tombe ( talk) 11:26, 27 May 2008 (UTC)
Brews, so what have you got to say about Anome's introducion of 'political centrifugal force' into the introduction? Would you delete it? David Tombe ( talk) 03:45, 28 May 2008 (UTC)
Anome, that doesn't mean that you have to remove the other part with it. You blended your political centrifugal force idea with colloquial centrifugal force as a means of being able to deny the need for rotation. Now that you realize that you can't do that, it is no excuse to remove the whole sentence. I'm going to put the original sentence back again as it was before you added the political bit. David Tombe ( talk) 05:50, 29 May 2008 (UTC)
It is saddening to see what terrible shape articles like planetary motion are in, where 1/10 the effort spent on the recalcitrant D Tombe would improve Wikipedia by several orders of magnitude. Brews ohare ( talk) 16:33, 27 May 2008 (UTC)
SBharris, the boxes above are sheer obfuscation and they totally neglect the fact that if centripetal force and centrifugal force both act radially then we can't switch one off and leave the other on.
In a circular motion, the radius remains constant. Hence the scalar quantity must be zero. We know that there is a radially inward centripetal force. But there must also be a radially outward centrifugal force. That's how the planetary orbital equation works.
Your boxes above were downright deceit to mask out the truths behind the planetary orbital equation and the fact that the artificial circle is a nonsense concept. David Tombe ( talk) 03:11, 28 May 2008 (UTC)
Hi Itub: Of course you are right, and David has been told this several times already with no apparent result. Brews ohare ( talk) 14:16, 28 May 2008 (UTC)
Itub, and how exactly do you reason that out? If the particle were moving in a straight line, it would already have an outward centrifugal force relative to the point origin in question. The centripetal force compounds with it to cancel it and cause curved path motion. When the two are exactly balanced we get circular motion and zero radial acceleration.
Can you not see that a straight line motion contains an outward centrifugal force realtive to any point that does not lie in its path? This is known as inertia. David Tombe ( talk) 05:55, 29 May 2008 (UTC)
Itub, the centrifugal force is in the radial direction. Your artificial circle uses the radial direction. You are trying far too hard to write off the centrifugal force by looking at the real example in the limited context of Newton's law of inertia. Newton's law of inertia is only god for cuboid kitchens. When we go to the cosmic scale or the microscopic scale, then the radial direction is the only direction that has any meaning. David Tombe ( talk) 09:39, 29 May 2008 (UTC)
I noticed yesterday that quite a bit of deceit went on. I added a clause to the introduction stating that centrifugal force had to be considered in conjunction with rotation.
Anome, knowing fine well that that is a true fact, for some reason doesn't want that fact mentioned.
So in order to obfuscate it, he blended the sentence in with the totally unrelated topic of 'political centrifugal force' as a cheap way of being able to claim that centrifugal force doesn't have to be connected with rotation.
This was a very cheap and pathetic tactic and it is totally contrary to wikipedia's rules.
So in order to expose what was going on, I split the sentence into two to clarify that we were talking about two totally unrelated topics.
Wolkeeper then comes in and reverts, citing the wikipedia rules that the pages are on topics and not terms.
But if Wolfkeeper had been genuine, he would simply have removed the political reference.
Instead, in an act of wikistalking and total hypocrisy, he retained the very subject that he was objecting to.
Wolfkeeper and Anome were clearly on opposite sides of the fence on this issue, but there would be no question of Wolfkeeper wanting to demonstrate any cracks in the united front.
So Wolfkeeper actually restored Anome's edit and the reference to political centrifugal force still remains, contary to wikipedia's rules.
Wolfkeeper was made fully aware of why I then re-reverted, but he just ignored it and reverted again.
That in my opinion suggests that there is no longer a serious scientific debate going on and that it has merely degenerated into the throwing of pies.
To clear this matter up, could we have a united statement from Wolfkeeper and Anome as to whether or not the political centrifugal force references should remain in the introduction?
I would imagine that any united decision will be totally steeped in politics, and neither in science nor wikipedia rules and regulations. David Tombe ( talk) 03:26, 28 May 2008 (UTC)
I think there's a problem with this article, beginning in the first sentence, where centrifugal force is defined as follows:
"Centrifugal force is a fictitious force that is associated with the centrifugal effect, which is an apparent acceleration that appears when describing physics in a rotating reference frame; centrifugal force appears to act on anything with mass considered in such a frame."
One problem with this attempted definition is that it refers to "rotating reference frames", whereas it should really refer to non-inertial coordinate systems, which need not be rotating. (I see there has been some discussion of this point previously - "polar coordinates" - but the point doesn't seem to have been absorbed or reflected in the article.) Perhaps it would be more paletable to replace "rotating reference frame" with "rotating or curved coordinate systems". TstoneT ( talk) 18:13, 28 May 2008 (UTC)
The main problem here is that most of the editors don't want to look at elliptical, hyperbolic, or general curved path motion. They want to focus exclusively on circular motion. That has been the cause of alot of the confusion.
Centrifugal force is something that is much more general than that which is associated with rotating frames of reference.
It is best to study the phenomenon from the perspective of polar coordinates in the inertial frame and to view centrifugal force as an absolute induced radial effect, induced by tangential motion.
If we are going to insist on clouding the issue with rotating frames of reference, then it will get confusing for cases of partial co-rotation because in reality we are only interested in the actual angular velocity of any particle in question.
The planetary orbital equation is about the best and most useful demonstration of centrifugal force in its general form. But from what I can see, there is a great reluctance on the part of the editors here to face up to elliptical or hyperbolic motion. David Tombe ( talk) 06:03, 29 May 2008 (UTC)
Wolfkeeper, you are too biased and too involved in maintaining a united opposition to everything that I say, for your opinions to be worth anything. David Tombe ( talk) 09:51, 29 May 2008 (UTC)
Polar coordinates yield very useful mathematical expressions. They yield the radial and the tangential forms of acceleration when it applies at right angles to the direction of motion.
But they don't describe any particular motion. They don't tell us if the effects are applied or induced or if the radial term is a centrifugal force or a centripetal force. It is only the vector convention which causes the radial convective force to point inwards.
In order to make full use of polar coordinates, we need to use them in conjunction with a real known physical situation.
The gravity orbit is a prime case in point. We select the expressions from the polar coordinates and apply them in the direction which we know makes physical sense. The radial convective term becomes an induced outward centrifugal force and we use Newton's gravity expression for the radially inward centripetal force.
Once we have applied the polar coordinates correctly to a real physical situation, then they become an excellent tool for analysis. They become considerably superior to the limited bastardization of the exact same maths, which is known as "rotating frames of reference".
A further example of the need to introduce physical reality before applying polar coordinates is the case of Kepler's law of areal velocity. It's an observed physical law. It means that we can eliminate the tangential terms. It means that there is no naturally occuring Coriolis force in free gravitational space. David Tombe ( talk) 06:57, 29 May 2008 (UTC)
Wolfkeeper, in your docking scenario you will have to introduce another angular velocity. It will be a three body problem.
The bottom line is that the three body problem is non-analytical and we do not need to consider it in order to understand what centrifugal force is about. In practice, it will all be done numerically on the computer.
It's interesting how keen you, Anome, and Timothy Rias are to introduce the three body problem which can't be accurately analyzed, yet you are totally averse to looking at the two body problem in planetary motion.
I can only conclude that none of you can understand two body planetary orbital theory and so you all sweep it under the carpet.
You much prefer to introduce the three body problem knowing that nobody can understand it. David Tombe ( talk) 05:07, 30 May 2008 (UTC)
Centrifugal force can be understood in its most general form in conjunction with planetary orbits. The general equation for any central force motion is a scalar equation and it takes the form,
Applied centripetal force + centrifugal force = m
where r is the radial length. In the case of planetary orbits, the centripetal force is the inward acting force of gravity.
The centrifugal force and the centripetal force that act on the same body are not necessarily balanced, and they should not be considered as an action-reaction pair. When they are balanced, we will have a circular motion, but even then the centrifugal force and the centripetal force should not be considered as an action-reaction pair because this is just a particular situation.
Newton's third law of motion is satisfied across two interacting bodies. For example, in the case of the Earth and the Moon, the centripetal force (gravity) that acts on the Earth is balanced by an equal and opposite centripetal force acting on the Moon. Likewise, the outward centrifugal force acting on the Moon is balanced by an equal and opposite centrifugal force acting on the Earth.
The reaction to a centripetal force across two bodies is sometimes called a reactive centrifugal force. The centripetal force and the reactive centrifugal force are always equal and opposite and they form an action-reaction pair. The reactive centrifugal force is essentially the centripetal force from the perspective of the other body.
In the gravity orbit, in the general case when the centripetal force and the centrifugal force are not balanced, the term will be non-zero and we will have an elliptical, parabolic, or hyperbolic orbit. David Tombe ( talk) 06:35, 29 May 2008 (UTC)
PeR, it's straight out of the advanced applied maths textbooks such as Goldstein's. Have you ever studied planetary orbital theory?
The whole point of polar coordinates is to concentrate exactly on the particle under consideration which in general will have a variable angular velocity.
I see absolutely nothing argumentative about this section. Your deletion of it from the main article was just a further example of your continual efforts to deny what centrifugal force is all about.
And it's strange how you were happy enough with the other sentence until I added the clause 'in connection with rotation'. It is your denial of the connection between actual rotation and centrifugal force which is the sole cause of this edit war. And the support you are getting from the crowd and the administration is a combination of corruption, bonding, and ignorance. David Tombe ( talk) 09:31, 29 May 2008 (UTC)
A few days ago, I predicted that the reference in the introduction to colloquial centrifugal force would soon vanish once you guys realized the implications of it.
It seems that I was correct. Anome's technique was to first mix it all up with 'political centrifugal force'. That was the obfuscation stage. The next stage was to remove the whole lot on the grounds that political centrifugal force was inappropriate.
Clearly we have group corruption going on in order to present a totally false and fictitious view of what centrifugal force is about.
Any whisper of centrifugal force being a real radial effect, is swiftly erased. David Tombe ( talk) 10:02, 29 May 2008 (UTC)
Then change it back to colloquial again. David Tombe ( talk) 10:16, 29 May 2008 (UTC)
Wolfkeeper, you are a wikistalker and a hypocrite and an absuser of administrative authority.
That edit of mine was already there for a long time and it didn't worry you before. I have got absolutely no confidence regarding your knowledge about this topic.
It is clear that you are here to push one big lie. David Tombe ( talk)
Wolfkeeper, you do not have the right to restrict this article to centrifugal force solely in connection with rotating reference frames. You have already created a dog's dinner by separating reactive centrifugal force to a separate page.
This article should mention centrifugal force in it's most general sense.
But it is quite obvious to everybody that you are just a wikistalker who is ganging up with a crowd who know nothing whatsoever about planetary orbital motion.
And because you know nothing about it, then nobody's allowed to know anything about it.
You are a totally corrupt editor who is being backed up by a crowd who need to learn a bit about centrifugal force before they are in a position to edit these pages David Tombe ( talk) 10:27, 29 May 2008 (UTC)
Wolfkeeper, the paragraph covered centrifugal force and nobody had objected to it when somebody else inserted it. It was only because I re-inserted it, after Anome deleted it in conjunction with his nonsense political centrifugal force idea, that you deleted it.
I get warnings in my tray not to accuse people of wikistalking even though it's quite permissible to go to the administrator's noticeboard and file a complaint of wikistalking.
You lot have broken the rules so many times that you can't be taken seriously.
You are a wikistalker if ever there was a wikistalker. And so is PeR. You are both top grade wikistalkers. And so are Anome and SCZenz.
Now if you don't like being exposed to the truth, then go ahead and do the honours, but I can assure you that you are a wikistalker.
It wouldn't matter what I put in the main article, whether it was sourced or not. You would routinely come along and delete it on the basis of a lie in the full knowledge that you are being supported by a crowd. You have a chip on your shoulder because you have been pushing a nonsense theory that has been exposed. David Tombe ( talk) 06:19, 30 May 2008 (UTC)
So what is the scope of this article? My intention was that it should only include D'Alembert forces as with this NASA page for example, but there's a <cough>persistent</cough> minority that want to include polar coordinate 'centrifugal forces' as well. I'm of the opinion that they're somewhat different, and certainly the associated coriolis terms are rather different. I think that if we integrate them the connectivity to other articles becomes problematic.- ( User) WolfKeeper ( Talk) 10:29, 29 May 2008 (UTC)
Anome, you must be joking. Analyzing two body planetary orbital theory is much easier in polar coordinates that it is in Cartesian coordinates. David Tombe ( talk) 05:10, 30 May 2008 (UTC)
A generalization of centrifugal force beyond a rotating frame would be to a frame in complicated motion. The general case is covered by this equation from fictitious force:
The article on centrifugal force treats the case of a fixed direction for the axis of rotation of the frame. A more general case would allow the frame Ω to vary in time both in direction and magnitude. If the observer moves in an elliptical or hyperbolic trajectory, the acceleration of the origin becomes a factor, as well as the rotational terms. The fictitious forces due to acceleration of the origin of the frame are not normally considered to be centrifugal or Coriolis terms.
It should be kept in mind that centrifugal force is not related to kinetics, but kinematics; therefore, introduction of mechanism is out of place, I'd say, and the role of planetary motion would be only as an example of a general approach for observational frames moving with time-dependent speed along 3-D curves with arbitrary Ω (t). So a frame fixed to the Earth has rotational aspects that include the precession of its Ω (t) (actually changing direction with time) and accelerations resulting from its elliptical rather than circular path around the Sun. The analysis of this case introduces secondary issues that possibly exceed the scope of an introductory article, and should be in another article. Brews ohare ( talk) 15:49, 29 May 2008 (UTC)
There are countless references for the fact that the radial fictitious force arising in stationary polar coordinates is called centrifugal force. Just to give two examples, with the relevant quotes:
(1) "An Introduction to the Coriolis Force" By Henry M. Stommel, Dennis W. Moore, 1989 Columbia University Press. "In this chapter we have faced the fact that there is something of a crisis in intuition that arises from the introduction of the polar coordinate system, even in a non-rotating system or reference frame. When we first use rectilinear coordinates to understand the dynamics of a particle, we commit our minds to the simple expressions x" = F_x, y" = F_y. We think of the accelerations as time rate-of change [per unit mass] of the linear momentum X' and y'. Then we express the same situation in polar coordinates that partly restore the wanted form. In the case of the radial component of the acceleration we move the r(theta')^2 term to the right hand side and call it a "centrifugal force."
(2) Statistical Mechanics By Donald Allan McQuarrie, 2000, University Science Books. "Since the force here is radial, it is convenient to use polar coordinates. Taking x = r cos(theta) and y = r sin(theta) [i.e., stationary polar coordinates] then... If we interpret the term [r(theta')^2] as a force, this is the well-known centrifugal force..."
Many more references can be provided it required. Frankly, this is not a particularly controversial point (aside from the editors of this wikipedia article, apparently). As I said before, centrifugal forces (like all inertial forces) are essentially defined as certain components that appear in the equations of motion when those equations are expressed in terms of non-inertial coordinates. In general, if we allow the coordinates to be curved in both space and time, several inertial terms appear in the equations of motion of a particle, and we call some of these terms “centrifugal”, some “Coriolis”, and some are given less familiar names, or aren’t named at all. If f is the mapping function to inertial coordinates, then all the inertial terms are of the form f_mn x^m/dt dx^n/dt with the understanding that the time coordinate is also one of the indexed “x^n” coordinates. It’s customary (and entirely reasonable) to call the diagonal terms “centrifugal” and the off-diagonal terms “Coriolis”. When you assert that stationary polar coordinates give something that looks like a centrigual force but really isn’t, you are sort of posing a zen riddle (like “Wagner’s music is better than it sounds”). It “looks” like a centrifugal force because it’s a diagonal term, it’s a fictitious force in non-inertial coordinates, and it points radially outward – all of which are essentially the definition of a centrifugal force.
PeR objected because he says the “theta dot squared” term refers to angular speed of the coordinate system in the case of centrifugal force, whereas it refers to angular speed of the particle in the case of stationary polar coordinates, so these are two different things. However, the motion of the particle and the motion of the (non-inertial) coordinates are defined relative to each other. In terms of stationary polar coordinates the value of theta is really just the angular position of the particle with respect to the coordinate system, and if that system is rotating, it simply adds to theta. In other words, if the coordinates have angular speed W and the particle has angular speed w relative to those coordinates, then the term that you claim should not be called centrifugal force is mr(W + w)^2, and of course this is the force that we would measure if we were holding the particle with a thread. It seems to me we would have to weave a fairly tangled web to claim that part of this is centrifugal force and part of it isn’t. We could expand the square, and call the W^2 term a centrifugal force and the 2Ww term a Coriolis force, but what would we call the w^2 term? A pseudo-centrifugal force? Or a double-secret-probation force? Bear in mind that all of these are purely fictitious forces, arising only because of the non-inertial coordinates. Anyone who doesn't like the "diagonal versus off-diagonal" criterion for classifying inertial forces as either cenrtifugal or Coriolis should propose a better one. I've provided references to reputable sources supporting my claims. TstoneT ( talk) 18:54, 29 May 2008 (UTC)
(3) Essential Mathematical Methods for Physicists By Hans-Jurgen Weber, George Brown Arfken, Academic Press, 2004, p 843.
(4) Methods of Applied Mathematics By Francis B. Hildebrand, 1992, Dover, p 156.
Since no one is voicing any objections, I go ahead and think about how to incorporate the more complete definition of centrifugal force into the article, hopefully correcting the mis-impression that it pertains only to rotating coordinate systems. TstoneT ( talk) 23:25, 29 May 2008 (UTC)
Brews, he's given citations for the very things that I have been arguing about. Polar coordinates in the inertial frame are the correct and standard way to analyze planetary orbital motion and the best way of elucidating centrifugal force as an outward radial effect.
The section that I put in yesterday was standard textbook planetary orbital theory. I mentioned Goldstein's.
I can only conclude that most of the editors here are schoolboys who have done the basic circular motion theory and are totally unwilling to examine the general cases of curved path motion such as ellipses and hyperbolae and the role of the radially outward centrifugal force.
I would say that my section was erased yesterday for no other reason than that nobody here could understand it since they have never done planetary orbital theory in advanced applied maths at university.
And in true schoolboy style, anything that they can't understand must go to the trash can. David Tombe ( talk) 05:22, 30 May 2008 (UTC)
I think there is one "trick" when trying to show a centrifugal force in polar coordinates. Look at eq. 1.48 in [22].
Here Fr is the "real" Newtonian force, which in the case of circular motion (that is, at constant r) is pointing constantly inwards and equals . That is, the only force is the centripetal force. However, if we say "wait a second, there is a term here, which looks just like Newton's equation for r!", we can rewrite equation 1.48 as (introducing the definition F′ for convenience):
This is exactly what McQuarry did. The problem is that F′ looks like a force for r, but it's not the "real" Newtonian force. So curiously enough, the centripetal force term from eq. 1.48 "changes sign" and turns into the centrifugal force term for Newton's force in a rotating frame. I argue that by insisting in treating F′ like a force, defined as , we are effectively "hopping on" to the rotating frame. That is, like SCZenz said above, just changing the coordinate system does not make the frame non-inertial. What makes it non-inertial is pretending that the product of mass and the second derivative of a coordinate is a force.
However, unlike a frame of reference that is rotating at a constant rate, the polar coordinates are always "following" the object in question. That is why, when cast in terms of polar coordinates, the Coriolis force is always tangential. There is no way of "moving tangentially"--if the object tries to move tangentially, φ speeds up or slows down to follow along, which results in a change of the centrifugal force term instead of a radial Coriolis term (the net effect is the same, of course). -- Itub ( talk) 09:58, 30 May 2008 (UTC)
When discussing a point particle as in the article planar motion, the equation for acceleration arises:
where the coordinate axes are attached to the particle and the radial direction is that of the displacement of the particle from some origin in an inertial frame. Using this formula, one can refer to a Coriolis force, an Euler force and a centrifugal force by adopting the moving reference frame attached to the particle.
This problem and its associated terminology although similar to that of this article, are not the same. This article refers to observational frames of reference and how trajectories described in such a frame are to be compared to those in an inertial frame. That objective is different from following a single particle from an inertial frame and describing its components of acceleration along various directions rather arbitrarily selected. I say arbitrarily selected, because the radial direction selected depends upon the origin of the observer, and will change even within the same inertial frame if the origin is chosen differently. This radial direction is not along the radius of curvature of the path, and its magnitude ρ is not the radius of curvature of the path (except for the very specific case of a circular path around the selected origin of coordinates), and so connection with centrifugal force cannot be made. The other component also is arbitrary as uθ is chosen orthogonal to the arbitrary direction of the displacement vector, and is not tangent to the path (except by accident). Brews ohare ( talk) 21:43, 29 May 2008 (UTC)
No Anome, what matters is the correct matching up of the maths to physical reality, and the polar coordinate system is the one that is tailor made to deal with concepts such as centrifugal force and Coriolis force.
The centrifugal force is a radial effect and the Coriolis force is a tangential effect.
But before we can use the expressions in polar coordinates we must construct a physical model of a real situation and then construct a differential equation around it, usually in the scalar variable of radial distance.
If you were in the slightest genuine about this topic, you would have read the section which I added to the main article yesterday. You would have blocked PeR for vandalism and wikistalking for having erased it on specious grounds.
It hardly needed sourced since it is standard planetary orbital theory which obviously none of you know anything about. In fact I did mention Goldstein's Classical Mechanics.
The picture that I am getting here is that the article has been hi-jacked by a group who have had a basic introduction to circular motion but who would be incapable of handling elliptical or hyperbolic motion and so they will all make sure that no such generalizations appear in the main article.
Your group has indulged in a number of deceitful tactics which I will now list.
(1) Making arguments in polar coordinates but jumping into Cartesian coordinates to conceal the flaws. The main example is circular motion, which is all that you seem to be capable of considering. You accept one moment that there is a radially outward centrifugal force balancing a radially inward centripetal force. But as soon as the centrifugal force becomes inconvenient for you, you claim that it vanishes in the inertial frame, even though the centripetal force remains. That is just a nonsense.
(2) Trying to drag in the three body problem while totally sweeping the two body problem under the carpet. This is because you feel more comfortable in a field that nobody can understand. It is good cover for talking nonsense.
(3) Introducing Lagrangian mechanics.
(4) Introducing Hamiltonian mechanics.
(5) Introducing matrix algebra.
(6) Quoting Feynam.
We have seen all these tactics used in a pathetic attempt to deny the fact that centrifugal force only occurs when a particle actually possesses an angular velocity relative to a point.
The section which I put in yesterday contained partically all that you need to know about centrifugal force. But that was too good for you. You much prefer that big mindless waffle of an introduction that tells us absolutely nothing about centrifugal force. David Tombe ( talk) 05:43, 30 May 2008 (UTC)
User:David Tombe has been blocked for a week for incivility and personal attacks. It is my strong recommendation that people not engage in discussion with him about his latest comments; it is extraordinarily unlikely to contribute to the project. If you must, please use his talk page. -- SCZenz ( talk) 06:34, 30 May 2008 (UTC)
You sir are a vindinctive and nasty person. You have harbored a personal animonisity towards Mr Tombe and your actions reflect your nasty character. You have consistently refused to treat him in a fair and civil manner in your efforts to block a full and objective discussion on these pages. You sir are the problem here, not Mr Tombe. Again I demand that you formally apologise to Mr Tombe for your personal animonisity and bias towards Mr Tombe. Your refusal to comply with past demands to do this demonstrates your personal lack of civility and personal mean spiritedness. You should be blocked from future actions of this nature and that would greatly improve the quality of discussions conducted here with wikipedia editors. It is my informed judgement that Mr Tombe has contributed more than you could possibility appreciate. The subject article is a dreadful mess. It reflects the ignorance of wikipedai editors and their continued resistence to learning the facts by educating themselves instead of repeating nonsense as if it were fact. 72.84.67.168 ( talk) 13:52, 30 May 2008 (UTC)
The equation for planar motion of a particle derived in planar motion:
is discussed by Taylor using the example of circular motion to introduce the notions of centripetal acceleration and what he calls "tangential" acceleration. The case of circular motion is unique however, because in this coordinate system polar coordinates actually are normal and tangential to the trajectory. Consequently, forces normal to and tangential to the trajectory, which have actual physical meaning, happen to be picked up by the polar coordinate system. However, to treat an elliptical path, for example, an elliptical coordinate system is necessary to make the coordinates tangential or normal to the path. If one were to do this, the tangential and centripetal forces could be picked out in this case too.
However, the application of polar coordinates to an elliptical path does not have this property. Consequently, determining the centripetal and tnagential forces in such a case is not straightforward, and attempts to cook it up are doomed to complexity.
Also, in a kinematic discussion, an elliptical orbit does not have to be traversed in the manner prescribed by the inverse square law. It is a perfectly proper application of kinematics to inquire what forces are necessary to traverse an elliptical path with position on the path an arbitrary function of time. Thus, the discussion of elliptical orbits can be divorced entirely from planetary motion for a kinematic discussion.
In the case of planetary motion, the force of gravity is always radially directed toward the Sun. That gives polar coordinates a special place in kinetics, but the connection of this radial force to the centripetal and tangential forces of kinematics is (a) complicated and (b) specific to this particular dynamic arrangement.
In sum, from the viewpoint of fictitious forces, polar coordinates are only special for circular motion, and for any other trajectory their value is moot. Brews ohare ( talk) 16:09, 30 May 2008 (UTC)