Consider a gas enclosed in a box. Let the walls have an area of 0.01m2. Let’s say a few molecules having their x-component of velocity =2m/s, hit a wall parallel to the yz plane. What will be the value of force on the wall in time dt? Let the number of molecules per unit volume be 10 & mass of each molecule be 10-20kg.

Correct Answer: 4*10-21N
According to the assumptions of KTG, we will assume that the molecules collide elastically. The total momentum transferred to the wall is 2mv*(1/2)nAvdt. 1/2 has been included because, on average, half the molecules near that wall will be moving away from the wall. Force will be momentum/time = nmAv2 = 10*10-20*0.01*4 = 4*10-21N.