Question

A molecule in a gas container hits a horizontal wall with speed 200 m $s^{-1}$ and angle ${30}^0$ with the normal, and rebounds with the same speed. Is momentum conserved in the collision ? Is the collision elastic or inelastic ?

Answer 1

Since the molecule approaches the wall of the container at a particular speed and then rebounds from the container at the same speed. Since there is no loss in the velocity due to any factor and the mass is same. So, the momentum of the system remains conserved.

The molecule approach and rebound with same speed. So, the kinetic energy of approach and rebound remains the same. Therefore it will an elastic collision.