A metal ball hits a wall and does not rebound whereas a rubber ball of the same mass on hitting the wall with the same velocity rebounds back. It can be concluded that

The change in momentum of metal ball after the collision with a wall is Δp=m(v2−v1)=m(0−v1)=−mv1 The change in momentum in rubber wall isΔp'=m(v2'−v1)=m(−v1−v1)=−2mv1                                       (∵v2'=−v1) Hence Δp'>Δp