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Consider these five situations:

  1. Gas container is placed in a fast moving train (assuming (train) its speed is constant).

  2. Liquid was instead put in the container and placed on moving train

  3. Gas container is "uniformly accelerated in a frictionless surface".

  4. Gas container which is not moving is observed from a "non inertial frame".

  5. Gas container which was moving with speed $v$ is uniformly decelerated to speed zero "(suddenly its not happening)".

In which of these cases Gas temperature will definitely increase or remains same? If it increases which energy gets converted to cause that? And what about the liquid one it surely will have a pressure gradient what about its temperature? Please explain what happens "microscopically with the gas molecules and the container walls".

I thought in moving cases the collisions would become more due to now the container moving so greater KE of gas particles, but thats not the case most likely. Ehat's going on thats I want to know.

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  • $\begingroup$ In case 1, is the container initially stationary, and then suddenly made to travel at the speed of the train? Is the container insulated? $\endgroup$
    – Chet Miller
    Commented Dec 14, 2021 at 12:30
  • $\begingroup$ This problem is not from relativity pls reopen it $\endgroup$
    – Orion_Pax
    Commented Dec 14, 2021 at 13:54
  • $\begingroup$ Yeah @Chet_Miller Sir $\endgroup$
    – Orion_Pax
    Commented Dec 14, 2021 at 13:55
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    $\begingroup$ @Orion_Pax As I explained in my answer to your other related question, if the gas (or liquid) is contained in a rigid (W=0), thermally insulated (Q=0) vessel, there will be no change in internal energy $\Delta U$, for all 5 situations since $\Delta U=Q-W$. For an ideal gas that will mean no change in equilibrium temperature, though there may be temperature and pressure gradients within the gas during acceleration, which disappear when equilibrium is re-established. $\endgroup$
    – Bob D
    Commented Dec 14, 2021 at 18:18
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    $\begingroup$ In case 1, as the container is accelerated, the gas nearer the trailing wall is compressed and the gas nearer the leading wall is expanded. If the acceleration is gradual, then the expansion and compression of the gas will be nearly reversible, and, in the end the work done to accelerate will match the final kinetic energy, so there will be no change in temperature. But, if the acceleration is very rapid, the expansion and compression will be somewhat irreversible, the work done on the gas will be greater than the final kinetic energy of the gas, and the temperature will rise. $\endgroup$
    – Chet Miller
    Commented Dec 17, 2021 at 11:39

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