The average time between successive collisions (relaxation time) for gas molecules, with molecular d

Question

The average time between successive collisions (relaxation time) for gas molecules, with molecular diameter $d$, number density $n$, and average speed $v_{avg}$ can be expressed as

Professor PC Thomas Classes · Answer

(a) : Mean free path for a gas is given by $\lambda = \frac{1}{\sqrt{2} n \pi d^2}$. The average time between successive collisions, or relaxation time $	au$, is the distance travelled between collisions divided by the average speed. Therefore, $	au = \frac{\lambda}{v_{avg}} = \frac{1}{\sqrt{2} n \pi d^2 v_{avg}}$.