Question

A ball hits the floor and rebounds after an inelastic collision. In this case, choose the correct alternative from the following.

• A. The momentum of the ball just after the collision is same as that just before the collision.
• B. The mechanical energy of the ball remains the same in the collision
• C. The total energy of the ball and earth is conserved
• D. The total momentum of the ball and earth is conserved

Answer 1

Answer: (C), (D)

The correct options are
C The total energy of the ball and earth is conserved
D The total momentum of the ball and earth is conserved

Under Inelastic collision,

Energy is lost in terms of heat,sound etc.

Hence Total energy of the Ball-Earth system is conserved but not the mechanical energy.

And, as we know momentum is a vector quantity and velocity of a body changes its direction on collision rebound,

hence velocity changes which in turn changes the momentum of the ball.

It can also be concluded by the fact that , when we take ball as a system then collision force will be external which can change the momentum of the system.

Similarly , in the Ball-Earth system , The collision force as well as gravitational force will be internal which can't affect the momentum of the system.

Hence option $\text{C,D}$ is correct.