Cooking Gas Containers: Temp Impact of Motion

[erisedk]

Homework Statement

Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside the containers will increase, decrease or stay the same?

Homework Equations

T is proportional to KE of gas molecules.

The Attempt at a Solution

I thought it would increase, because the average KE of the gas molecules would increase. But the answer says stays the same.

 

[Buzz Bloom]

Hi erisedk:

I think you forgot that temperature is a measure of the average kinetic energy (KE) with respect to the center of mass of the material. Although the KE is increased with respect to a fixed point on the ground, that increase is irrelevant to temperature.

Regards,
Buzz

 

[erisedk]

Thank you, I definitely don't think I even knew that. If the car were accelerating, would the temperature still not change because the increase in velocity would occur for the centre of mass as well?

 

[Buzz Bloom]

If the car were accelerating, would the temperature still not change because the increase in velocity would occur for the centre of mass as well?

Hi erisedk:

Temperature does not include the KE of the center of mass (COM). It is the proportional to the average of the KE of the particles relative to the COM. That is, for each particle its

KE = 1/2 mv²​

where v is the velocity of the particle relative to the systems COM.

Regards,
Buzz

 

[erisedk]

Oh yeah, I got that. So even if it were accelerating, no change in temperature right?

 

[Buzz Bloom]

Hi erisedk:

Right.

Regards,
Buzz

 

[erisedk]

Thank you :)