Question

A cubic vessel (with faces horizontal + vertical) contains an ideal gas at NTP. The vessel is being carried by a rocket which is moving at a speed of 500$m{s}^{-1}$ in vertical direction. The pressure of the gas inside the vessel as observed by us on the ground

• A. Remains the same because 500 m/s is very much smaller than $V_{rms}$ of the gas
• B. Remains the same because motion of the vessel as a whole does not affect the relative motion of the gas molecules and the walls
• C. Will increase by a factor equal to $\frac{v_{rms}^2+(500{)}^2}{v_{rms}^2}where{v}_{rms}$ was the original mean square velocity of the gas
• D. Will be different on the top wall and bottom wall of the vessel

Answer 1

The correct option is B Remains the same because motion of the vessel as a whole does not affect the relative motion of the gas molecules and the walls

This brings in concepts of relative motion and that when collision takes place, it is the relative velocity which changes