Question

When a molecule moving with velocity u collides normally with the wall of the container, then the change in its velocity and momentum will be :

• A. -u and mu
• B. 2u and 2 mu
• C. 2u and mu
• D. u and -mu

Answer 1

The correct option is B 2u and 2 mu

Mass of the molecule is negligibly small compared to mass of the container. So, when the molecule hits the wall of the container with a velocity 'u', it will rebound with the same speed.
By assuming the energy loss during the collision is zero.
the change in velocity is 2u and change in momentum is 2mu.