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Why in Aresol Cans and spray paint cans is there ball inside that makes a noise when you shake it? x
Please reply the fate of the world rests upon it... —Preceding unsigned comment added by 80.176.73.246 ( talk) 00:51, 5 May 2008 (UTC)
Moved from Talk:Dry ice: Is there any other substance that forms a "dry ice"? Samw ( talk) 03:09, 5 May 2008 (UTC)
To have something resembling "dry ice" you need to have a substance with a triple point pressure that is higher than the atmospheric pressure and a sublimation point below room temperature (this second requirement is so that the substance feels cold). From the common substances listed in this table [1], only acetylene (and CO2) meets the requirements, assuming you want your dry ice to be dry at sea level, which is 101 kPa. If you are willing to move up to the mountains, a couple other substances could work. For example, xenon and nitrous oxide could form dry ices in Mexico City, where the ambient pressure is around 78 kPa. And if you use a vacuum pump with low enough pressure, many other substances can be made to behave like dry ice. A couple of the substances in the table, graphite and uranium hexafluoride, have high enough triple point pressures so that they will never be a stable liquid under normal pressure, but their sublimation point is higher (for graphite much higher) than room temperature, so I am reluctant to call them "ices". -- Itub ( talk) 12:52, 6 May 2008 (UTC)
When examining the power to weight ratio of an automobile, comparing it to another, horsepower per lb. or kg. is considered. I'm wondering if a torque to weight ratio should be given consideration. If so, should it be given equal consideration as horsepower, a certain amount of consideration, or none at all? Note: peak RPM, aerodynamics, and other values are not important to me at this time, just power to weight ratio. Thanks. MoeJade ( talk) 04:41, 5 May 2008 (UTC)
-Thanks for the fast response, Wisdom89! So would you give torque to weight ratio equal consideration, averaging power to weight and torque to weight together? Or does power to weight take precedense (sp?), with torque considered, but not given as much weight? MoeJade ( talk) 04:54, 5 May 2008 (UTC)
O.k. Good input. Basically, a friend and I were comparing two vehicles for potential acceleration. Car A has 221 HP, 236 f/lb. of torque, and weighs 1430 kg. Its power to weight ratio is 0.154, or 0.154 HP per kg. Car B has 216 HP, 152 f/lb. of torque, and weighs 1180 kg. Its power to weight ratio is 0.183, which is notably better than car A. However, car A has 236 f/lb. of torque, or a torque to weight ratio of 0.165, which is substantially better than car B's torque to weight ratio of 0.128. Observing power to weight ratio only, car B wins easily. But, with car A's significant amount of torque,and its significant torque to weight ratio, it's a tougher choice than it looks, to me, anyway. Any additional comments on this are welcome. MoeJade ( talk) 13:52, 5 May 2008 (UTC)
There is a paragraph in article Electron I don't get it well:
As my understanding, it tells us that an electron DOSE occupy space (its radius is 2.8179 × 10−15 m according to the article) and also it somewhat explains why an electron occupies space. But I'm afraid it doesn't help for understanding the reason why electron occupies space, especially:
the sentences above are confusing to me...dose anyone know what do they mean?
Additional question: What if we force two electrons collide? Will they just overlap with each other and then pass through without collision?
(solving the questions above might involve some QFT and/or QED but they are too tough to me) - Justin545 ( talk) 06:06, 5 May 2008 (UTC)
In answer to the second question, since they occupy space, they can't just go through each other. They will collide and bounce apart. Leeboyge ( talk) 07:22, 5 May 2008 (UTC)
Sticking my nose temerariously into a question well outside my expertise: I think the answer is that, as of 2008, no one really knows whether the electron (in the sense of the bare charge, not the cloud of virtual electrons and positrons that surround it) occupies space. My understanding is that QED takes it to be a point charge, occupying no space, and having therefore infinite density (and by the way also infinite charge -- the cloud of virtual particles surrounding it "shield" most of that charge). QED works extraordinarily well, but the extent to which it faithfully represents the underlying reality, as opposed to simply being a collection of hacks that get the right answer -- again, nobody knows. -- Trovatore ( talk) 08:28, 5 May 2008 (UTC)
I'm afraid it depends on what you mean by "occupy space". If you want the everyday-scale notion of occupying space to extend down to the quantum level then I think you're pretty much forced to say that electrons do occupy space, since most of the space supposedly "occupied" by solid objects only has electron orbitals in it. The space occupied by an electron in this sense has nothing to do with any intrinsic size. A hydrogen atom and a He+ ion both have a single electron orbiting a nucleus, but the former is larger than the latter because of the different nuclear charge, even though it's an identical electron that occupies most of the space.
Protons and neutrons do have an intrinsic size: they're bound states of more fundamental particles (much like an atom is), and the bound state has a characteristic radius (much like an atom does). People have proposed preon theories where the electron is a composite particle, but none of them have had much success. If an electron were composed of preons then I suppose it would have a size in this sense, but I don't know much about this.
Strings (from string theory) have a characteristic size but don't really occupy space, being one-dimensional subsets of a three-or-more-dimensional space.
It seems fairly likely that future physical theories won't have a concept of "space" any more (except as a large-scale approximation), which will make this question even harder to answer.
2.8179 × 10−15 m is the classical electron radius. Ignore it, it's meaningless. -- BenRG ( talk) 10:28, 5 May 2008 (UTC)
To make the conclusion, I presume:
the conclusion above may sound ridiculous. Please point out my errors if any. - Justin545 ( talk) 01:53, 6 May 2008 (UTC)
This isn't homework, it's part of my revision material and I need some help with understanding it. I'm not asking for an answer.
A filament bulb is connected to the 230V mains power supply and a meter indicates that 31 coulombs of charge flows in a period of 60 seconds. Calculate: a) the total electrical energy transferred to another form by the lamp b) the power dissipated by the lamp
Am I right in assuming that 31 coulombs of charge per 60 seconds is roughly 0.52 Amps since an amp is the flow of charge per second? My problem is i've forgotten whichever equation to use to calculate the electrical energy transferred.
As for part B, i'm right in assuming I need to use P = I^2 x V for this?
Regards, CycloneNimrod Talk? 10:47, 5 May 2008 (UTC)
A curiosity of the English usage difference between the UK and the U.S. is the British use of "revise" when we would say "review" or "study." On this side of the pond, to "revise" would only mean "to edit and make changes." Edison ( talk) 18:44, 5 May 2008 (UTC)
How different are these two times? Is the difference always the same or does it vary?
Thank you. Wanderer57 ( talk) 13:34, 5 May 2008 (UTC)
I've got a couple of questions I hope somebody can answer. Thank you.
Thanks again. 83.37.4.200 ( talk) 14:23, 5 May 2008 (UTC)
I'm working on an account of Henry IV's love life. In his biography of Henry, David Buisseret writes: "Towards the end of the month he had another attack of gonorrhoea, which gave rise to a temporary but alarming heart condition". Could anyone tell me if temporary heart conditions can indeed be brought on by gonorrhoea? (Historians sometimes repeat this sort of thing without question, so I need to check this out.) The incident is important because Henry nearly died. Many thanks. qp10qp ( talk) 15:06, 5 May 2008 (UTC)
what is the method of minimising resistance to treatment in tuberculosis? 172.159.163.56 ( talk) 16:27, 5 May 2008 (UTC)
There are two species of Laurelia, one native to the Andes - Laurelia sempervirens (Chilean Laurel, Peruvian Laurel, Peruvian Nutmeg) and the other found in New Zealand - Laurelia novae-zelandiae (Pukatea) .
When I saw one of these trees, growing at Enys in Cornwall, UK, yesterday, the Head Gardener said they were examples of "Gondwanan distribution". I have looked at the Gondwana article, but this is very brief on the topic, which is a REDIRECT to Godwana.
I would like to know more about the differences between the two species and when, approximately, they diverged, due to the separation of New Zealand and South America from the Gondwanan continent. Vernon White . . . Talk 19:24, 5 May 2008 (UTC)
Which field fo engineering is the most multidiciplinary i.e. which concerns the widest range of topics from maths, physics, chemistry, geography, biology etc. Clover345 ( talk) 20:53, 5 May 2008 (UTC)
Possibly constructions with biopolymers while exploiting advantages geological features. You know these disciplines are just groups into which we categorise knowledge, they interconnect depending on how do you define there disciplines Bastard Soap ( talk) 21:21, 5 May 2008 (UTC)
Can anyone please explain to me what makes the little buggers vibrate about? Bastard Soap ( talk) 21:16, 5 May 2008 (UTC)
I knew that heat makes them vibrate, my question is why is it so? Bastard Soap ( talk) 18:32, 6 May 2008 (UTC)
My question is still why and how do the molecules vibrate? I know that the energy of heat has to go somewhere, I just don't understand what system causes it to vibrate. Bastard Soap ( talk) 17:26, 7 May 2008 (UTC)
Science desk | ||
---|---|---|
< May 4 | << Apr | May | Jun >> | May 6 > |
Welcome to the Wikipedia Science Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
Why in Aresol Cans and spray paint cans is there ball inside that makes a noise when you shake it? x
Please reply the fate of the world rests upon it... —Preceding unsigned comment added by 80.176.73.246 ( talk) 00:51, 5 May 2008 (UTC)
Moved from Talk:Dry ice: Is there any other substance that forms a "dry ice"? Samw ( talk) 03:09, 5 May 2008 (UTC)
To have something resembling "dry ice" you need to have a substance with a triple point pressure that is higher than the atmospheric pressure and a sublimation point below room temperature (this second requirement is so that the substance feels cold). From the common substances listed in this table [1], only acetylene (and CO2) meets the requirements, assuming you want your dry ice to be dry at sea level, which is 101 kPa. If you are willing to move up to the mountains, a couple other substances could work. For example, xenon and nitrous oxide could form dry ices in Mexico City, where the ambient pressure is around 78 kPa. And if you use a vacuum pump with low enough pressure, many other substances can be made to behave like dry ice. A couple of the substances in the table, graphite and uranium hexafluoride, have high enough triple point pressures so that they will never be a stable liquid under normal pressure, but their sublimation point is higher (for graphite much higher) than room temperature, so I am reluctant to call them "ices". -- Itub ( talk) 12:52, 6 May 2008 (UTC)
When examining the power to weight ratio of an automobile, comparing it to another, horsepower per lb. or kg. is considered. I'm wondering if a torque to weight ratio should be given consideration. If so, should it be given equal consideration as horsepower, a certain amount of consideration, or none at all? Note: peak RPM, aerodynamics, and other values are not important to me at this time, just power to weight ratio. Thanks. MoeJade ( talk) 04:41, 5 May 2008 (UTC)
-Thanks for the fast response, Wisdom89! So would you give torque to weight ratio equal consideration, averaging power to weight and torque to weight together? Or does power to weight take precedense (sp?), with torque considered, but not given as much weight? MoeJade ( talk) 04:54, 5 May 2008 (UTC)
O.k. Good input. Basically, a friend and I were comparing two vehicles for potential acceleration. Car A has 221 HP, 236 f/lb. of torque, and weighs 1430 kg. Its power to weight ratio is 0.154, or 0.154 HP per kg. Car B has 216 HP, 152 f/lb. of torque, and weighs 1180 kg. Its power to weight ratio is 0.183, which is notably better than car A. However, car A has 236 f/lb. of torque, or a torque to weight ratio of 0.165, which is substantially better than car B's torque to weight ratio of 0.128. Observing power to weight ratio only, car B wins easily. But, with car A's significant amount of torque,and its significant torque to weight ratio, it's a tougher choice than it looks, to me, anyway. Any additional comments on this are welcome. MoeJade ( talk) 13:52, 5 May 2008 (UTC)
There is a paragraph in article Electron I don't get it well:
As my understanding, it tells us that an electron DOSE occupy space (its radius is 2.8179 × 10−15 m according to the article) and also it somewhat explains why an electron occupies space. But I'm afraid it doesn't help for understanding the reason why electron occupies space, especially:
the sentences above are confusing to me...dose anyone know what do they mean?
Additional question: What if we force two electrons collide? Will they just overlap with each other and then pass through without collision?
(solving the questions above might involve some QFT and/or QED but they are too tough to me) - Justin545 ( talk) 06:06, 5 May 2008 (UTC)
In answer to the second question, since they occupy space, they can't just go through each other. They will collide and bounce apart. Leeboyge ( talk) 07:22, 5 May 2008 (UTC)
Sticking my nose temerariously into a question well outside my expertise: I think the answer is that, as of 2008, no one really knows whether the electron (in the sense of the bare charge, not the cloud of virtual electrons and positrons that surround it) occupies space. My understanding is that QED takes it to be a point charge, occupying no space, and having therefore infinite density (and by the way also infinite charge -- the cloud of virtual particles surrounding it "shield" most of that charge). QED works extraordinarily well, but the extent to which it faithfully represents the underlying reality, as opposed to simply being a collection of hacks that get the right answer -- again, nobody knows. -- Trovatore ( talk) 08:28, 5 May 2008 (UTC)
I'm afraid it depends on what you mean by "occupy space". If you want the everyday-scale notion of occupying space to extend down to the quantum level then I think you're pretty much forced to say that electrons do occupy space, since most of the space supposedly "occupied" by solid objects only has electron orbitals in it. The space occupied by an electron in this sense has nothing to do with any intrinsic size. A hydrogen atom and a He+ ion both have a single electron orbiting a nucleus, but the former is larger than the latter because of the different nuclear charge, even though it's an identical electron that occupies most of the space.
Protons and neutrons do have an intrinsic size: they're bound states of more fundamental particles (much like an atom is), and the bound state has a characteristic radius (much like an atom does). People have proposed preon theories where the electron is a composite particle, but none of them have had much success. If an electron were composed of preons then I suppose it would have a size in this sense, but I don't know much about this.
Strings (from string theory) have a characteristic size but don't really occupy space, being one-dimensional subsets of a three-or-more-dimensional space.
It seems fairly likely that future physical theories won't have a concept of "space" any more (except as a large-scale approximation), which will make this question even harder to answer.
2.8179 × 10−15 m is the classical electron radius. Ignore it, it's meaningless. -- BenRG ( talk) 10:28, 5 May 2008 (UTC)
To make the conclusion, I presume:
the conclusion above may sound ridiculous. Please point out my errors if any. - Justin545 ( talk) 01:53, 6 May 2008 (UTC)
This isn't homework, it's part of my revision material and I need some help with understanding it. I'm not asking for an answer.
A filament bulb is connected to the 230V mains power supply and a meter indicates that 31 coulombs of charge flows in a period of 60 seconds. Calculate: a) the total electrical energy transferred to another form by the lamp b) the power dissipated by the lamp
Am I right in assuming that 31 coulombs of charge per 60 seconds is roughly 0.52 Amps since an amp is the flow of charge per second? My problem is i've forgotten whichever equation to use to calculate the electrical energy transferred.
As for part B, i'm right in assuming I need to use P = I^2 x V for this?
Regards, CycloneNimrod Talk? 10:47, 5 May 2008 (UTC)
A curiosity of the English usage difference between the UK and the U.S. is the British use of "revise" when we would say "review" or "study." On this side of the pond, to "revise" would only mean "to edit and make changes." Edison ( talk) 18:44, 5 May 2008 (UTC)
How different are these two times? Is the difference always the same or does it vary?
Thank you. Wanderer57 ( talk) 13:34, 5 May 2008 (UTC)
I've got a couple of questions I hope somebody can answer. Thank you.
Thanks again. 83.37.4.200 ( talk) 14:23, 5 May 2008 (UTC)
I'm working on an account of Henry IV's love life. In his biography of Henry, David Buisseret writes: "Towards the end of the month he had another attack of gonorrhoea, which gave rise to a temporary but alarming heart condition". Could anyone tell me if temporary heart conditions can indeed be brought on by gonorrhoea? (Historians sometimes repeat this sort of thing without question, so I need to check this out.) The incident is important because Henry nearly died. Many thanks. qp10qp ( talk) 15:06, 5 May 2008 (UTC)
what is the method of minimising resistance to treatment in tuberculosis? 172.159.163.56 ( talk) 16:27, 5 May 2008 (UTC)
There are two species of Laurelia, one native to the Andes - Laurelia sempervirens (Chilean Laurel, Peruvian Laurel, Peruvian Nutmeg) and the other found in New Zealand - Laurelia novae-zelandiae (Pukatea) .
When I saw one of these trees, growing at Enys in Cornwall, UK, yesterday, the Head Gardener said they were examples of "Gondwanan distribution". I have looked at the Gondwana article, but this is very brief on the topic, which is a REDIRECT to Godwana.
I would like to know more about the differences between the two species and when, approximately, they diverged, due to the separation of New Zealand and South America from the Gondwanan continent. Vernon White . . . Talk 19:24, 5 May 2008 (UTC)
Which field fo engineering is the most multidiciplinary i.e. which concerns the widest range of topics from maths, physics, chemistry, geography, biology etc. Clover345 ( talk) 20:53, 5 May 2008 (UTC)
Possibly constructions with biopolymers while exploiting advantages geological features. You know these disciplines are just groups into which we categorise knowledge, they interconnect depending on how do you define there disciplines Bastard Soap ( talk) 21:21, 5 May 2008 (UTC)
Can anyone please explain to me what makes the little buggers vibrate about? Bastard Soap ( talk) 21:16, 5 May 2008 (UTC)
I knew that heat makes them vibrate, my question is why is it so? Bastard Soap ( talk) 18:32, 6 May 2008 (UTC)
My question is still why and how do the molecules vibrate? I know that the energy of heat has to go somewhere, I just don't understand what system causes it to vibrate. Bastard Soap ( talk) 17:26, 7 May 2008 (UTC)