I learned that thermal energy is just the kinetic energy of the individual particles of a substance. What if I give the ice cube kinetic energy, not by heating it, but rather by making it move very fast? Then the ice particles will gain kinetic energy because they are now moving very quickly, translationally through space. Therefore, since they have more kinetic energy then the temperature must also increase. Since the temperature increases it melts. I feel like this must be wrong but I don't know why.
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No it would not. Translation of the center of mass of an object is not the same thing as heating it up. – Jon Custer Feb 15 '24 at 22:04
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@JonCuster but doesn't each individual particle have its own center of mass? Each one of those particles has more kinetic energy because the whole ice cube is moving. So how is that kinetic energy of translation different than the kinetic energy of heat? – NightwindArcher Feb 15 '24 at 22:08
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The velocity distribution of the particles relative to each other is what determines the temperature of the body. So one can subtract out the velocity of the center of mass. – Jon Custer Feb 15 '24 at 22:19
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2An ice cube at rest from your point of view is moving near the speed of light in many other inertial frames. You seem to be thinking that motion is absolute, but it’s not. – Ghoster Feb 15 '24 at 22:51
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Heat will be produced during acceleration until the body reaches a constant speed. – Stevan V. Saban Feb 15 '24 at 23:19
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Does this answer your question? If temperature is related to average kinetic energy in an ideal gas, then does speeding up the gas container affect its temperature? – Chemomechanics Feb 15 '24 at 23:22
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Realistically, there is no such thing as a perfect vacuum. So the mean free path of any particle is finite. Eventually, there will be a collision that generates heat. – Stevan V. Saban Feb 15 '24 at 23:28
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No, the orderly movement of the body as whole does not contribute to its thermal energy. Only the random movement of its particles does.
Quoted from "Thermal Energy | Energy Fundamentals" at University Leipzig (emphasis by me):
In thermodynamics, the internal energy $U$ is an energy form that results from the random motion of microscopic particles in a system. This thermal energy increases with increasing temperature $T$.
Thomas Fritsch
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