Question

A ball moving with velocity v strikes a wall moving towards the ball with velocity u . An elastic impact lasts for t seconds. Then the mean elastic force acting on ball is?

Answer 1

An elastic collision is defined as one in which both conservation of momentum and conservation of kinetic energy are observed.

This implies that there is no dissipative force acting during the collision and that all of the kinetic energy of the objects before the collision is still in the form of kinetic energy afterward.

Let us take positive X - axis in the direction of initial motion of the body.

If i is unit vector in this direction, the initial momentum of the body is p1=MVi.

The final momentum is P2=-MVi.

The change in momentum = final momentum - initial momentum. Therefore,Change in momentum=p2-p1=-MVi-MVi=-2MVi