Temperature/Kinetic Energy Question

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Discussion Overview

The discussion revolves around the relationship between temperature and kinetic energy, specifically questioning whether the motion of a ball in space affects its temperature due to increased kinetic energy of its molecules.

Discussion Character

  • Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asserts that temperature is defined as the average kinetic energy of molecules, questioning if a moving ball in space would have a higher temperature due to its increased speed.
  • Another participant suggests that any increase in temperature would be negligible when considering the kinetic energy gain distributed across all atoms in the ball.
  • A third participant argues that temperature must be measured from a frame where the center of mass of the object is at rest, implying that the ball's motion does not affect its temperature.
  • A later reply reiterates the point about temperature being frame-dependent and expresses regret for not considering this earlier.

Areas of Agreement / Disagreement

Participants express disagreement regarding the relationship between the ball's motion and its temperature, with some asserting that motion does not affect temperature while others suggest a negligible effect.

Contextual Notes

The discussion does not resolve the implications of frame dependence on temperature measurement and the assumptions involved in defining kinetic energy in different reference frames.

Hyphon
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Just a quick question:

I have always been told that the temperature of a substance was a measurement of the average kinetic energy of the molecules. If I were to throw a ball in space (i.e no air resistance), does this mean the ball now has a higher temperature since it is moving faster and all its molecules have a higher kinetic energy?

Thanks
 
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I suppose the possible difference would be neglible. Divide the KE gain over all the atoms in the ball and you're going to get a really really really small number.
 
No. Temperature is a measure of the average KE of the molecules measured from a frame in which the center of mass of the object is at rest. (Otherwise temperature would be frame dependent.)

You might find this discussion helpful: https://www.physicsforums.com/showthread.php?t=75824
 
Doc Al said:
No. Temperature is a measure of the average KE of the molecules measured from a frame in which the center of mass of the object is at rest. (Otherwise temperature would be frame dependent.)

Damn it. That's what I get for not thinking things through before posting. And it's so obvious too.
 

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