Question

A ball hits the floor and rebounds after an inelastic collision in this case
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 momentum of the ball and the earth is conserved
D. The total energy of the ball and the earth remains the same

Answer 1

When the net external force on the system is zero the total momentum of the system remains conserved. So, this question will be solved by applying momentum conservation.

Complete step by step solution: In the question it is given that the ball collides with the floor if we consider the ball and the floor as the system then there is no external force acting on the system and hence the total momentum of the system i.e.( the earth and the ball) remains conserved. The force exerted by the ball on earth and the force exerted by the earth on the ball is internal force and due to internal force momentum of the system does not change.

Hence the correct answer will be option “C”.

Note: 1. During collision energy of the system do not remain conserved as some energy losses in the form of heat and sound
2. Momentum of the individual body may change during collision but the total momentum of the whole system remains conserved. So, we apply momentum conservation for the whole system, not for individual body.