question_answer 15)

                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 \[500\,m\,{{s}^{-1}}\] is very much smaller than \[{{\upsilon }_{rms}}\] 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 \[{{\upsilon }^{2}}_{rms}+{{(500)}^{2}})/{{\upsilon }^{2}}\,rms,\] where \[{{\upsilon }_{rms}}\] was the original mean square velocity of the gas.                 (d) will be different on the top wall and bottom wall of the vessel.

Answer:

                (b) As \[P=\,\frac{1}{2}\,\rho {{c}^{2}}\], it (i.e., P) remains unaffected as n, R, T and V are constants. In fact, (b) is self-explanatory.