Question

A lump of putty and a rubber ball have equal mass. Both are thrown with equal speed against a wall. The putty sticks to the wall. The ball bounces back at nearly the same speed with which it hit the wall. Which object experiences the greater momentum change?a. They both experience the same momentum change.

b. The putty experiences the greater momentum change.
c. The ball experiences the greater momentum change.
d. Not enough information is given to determine the answer.

Answer 1

Option (c). The ball experiences the greater momentum change.

Step-by-step explanation:

Suppose the initial momentum of the putty and the ball is
`mv`.

Since the final velocity of the putty is zero, it final momentum must be zero, too. So its momentum was reduced in
`mv`.

In the case of the ball, we have that its final speed is the same, but its final velocity has opposite direction. As the velocity and the momentum are vectors, the direction is relevant. Taking this into account, the final momentum of the ball is
`-mv`. So, its momentum was reduced in
`2mv`.

This leads us to the conclussion that the rubber ball experiences a greater momentum change than the lump of putty. This is the option (c).