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wildkat7411
- 5
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I understand that friction is the force that opposes motion and that rubbing two objects togethere generate heat. But what is the cause of this release of energy?
I also have an indirect reason for there being a heat, possibly a more physics relevant one, even though mgb is right. something moving has energy. say you slide a piece of wood on the floor and you give the wood 100 joules of energy. eventually the floor's friction with the wood will make the wood stop. where did that energy go?
I disagree with the above answers, I claim nobody knows why. Arguments regarding deformation of orbitals are not very rigorous; the electromagnetic force is conservative, and so any postulated deformation is *elastic*, and the energy is still available to perform work, as opposed to being dissipated.
Is it available to do work? If I have a network of springs (not a bad model for a solid) and I do work to stretch one and release it, it seems like the energy will be immediately dissipated as vibrations throughout the material.
Is it available to do work? If I have a network of springs (not a bad model for a solid) and I do work to stretch one and release it, it seems like the energy will be immediately dissipated as vibrations throughout the material.
It's not dissipated- you are describing *sound*. Call it phonons if you want.
I'm not sure that's the *whole* point of thermodynamics- Thermodynamics concerns itself with the flow and transformation of energy in matter.
But, your comment points out interesting connections between temperature, entropy, and heat. Your comment is certainly true for 0 K, but not for any other temperature.
Phonons are often invoked to predict thermal conductivity (and other properties) in materials, which is not the same thing as heat. Phonon gases are analogous to particle gases by replacing 'pressure' with 'temperature'.
http://www.springerlink.com/content/c5gk8m24g8506101/
Yes, but note that the very notion of temperature (in the precise thermodynamic sense) already assumes that you have performed a coarse graining and are describing the system statistically. If you don't do this (and in practice you have no choice but to do this), then the system is always in some pecisely known microstate, the entropy is then the fine grained entropy which is zero.
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This is known as Laplace's demon and it simply demonstrates that notions such as heat, entropy and temperature arise when we have a lack of information about the system.