Q 11-12-127JEE MainJEE Main 2020 (2 Sep, Shift 2)Medium
An ideal gas in a closed container is slowly heated. As its temperature increases, which of the following statements are true?
(A) The mean free path of the molecules decreases.
(B) The mean collision time between the molecules decreases.
(C) The mean free path remains unchanged.
(D) The mean collision time remains unchanged.
Answer: (A) (B) and (C)
In a closed container the number density $n$ stays constant, so the mean free path $\lambda = \dfrac{1}{\sqrt2\pi d^{2}n}$ is unchanged.
The mean speed increases with temperature, so the mean collision time $\tau = \lambda/\bar v$ decreases. Hence (B) and (C) are true.
Solution by Sreeraj P, M.Sc Physics