Question

A ball strikes the wall and rebounds with the same speed. If initial momentum is ‘P’ the change in momentum will be:

• A. 0.0
• B. 2P
• C. -2P
• D. -P

Answer 1

The correct option is C -2P

Final momentum is negative because velocity is changed to opposite direction.

Also, magnitude of momentum will not change after bouncing. This is because the momentum is the product of mass and velocity. It is given that the speed does not change. Mass also remains conserved.

So, final momentum is:
$p_f=-P$

Change in momentum is:
$\Delta p=p_f-p_i$
$\Delta p=-P-P$
$\Delta p=-2P$