Question
A molecule in a gas container hits a horizontal wall with speed 200 m/s at angle 30° with normal and rebounds with same speed. Is momentum of molecule conserved in the collision? Is the collision elastic or inelastic?
Solution
Momentum is a vector quantity, therefore, though its magnitude remains constant, its direction changes, hence the momentum will change. After collision, the direction of motion and hence momentum changes, therefore, momentum of molecule will not remain conserved.
Since the speed of molecule remains constant, its kinetic energy remains conserved. Therefore collision is an example of elastic collision.
