Kinetic Theory Of Gases Question 135

Question: Consider a gas with density $ \rho $ and $ \bar{c} $ as the root mean square velocity of its molecules contained in a volume. If the system moves as whole with velocity v, then the pressure exerted by the gas is

Options:

A) $ \frac{1}{3}\rho ,{{\bar{c}}^{2}} $

B) $ \frac{1}{3}\rho {{(c+v)}^{2}} $

C) $ \frac{1}{3}\rho {{(\bar{c}-v)}^{2}} $

D) $ \frac{1}{3}\rho {{({{c}^{-2}}-v)}^{2}} $

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Answer:

Correct Answer: A

Solution:

[a] Pressure of the gas will not affected by motion of the system, hence by $ v _{rms}=\sqrt{\frac{3P}{\rho }} $

Therefore $ {{\bar{c}}^{2}}=\frac{3P}{\rho } $

Therefore $ P=\frac{1}{3}\rho {{\bar{c}}^{2}} $