Two balls have equal mass, but are made from different types of rubber. The balls are released from rest and each falls through the same height before colliding with a concrete floor. Both balls impact the floor with the same velocity, but one ball bounces back to the same height from which it was dropped $($elastic collision$)$ while the other doesn't bounce at all $($inelastic$).$ If both collisions last for the same amount of time, then the impulse is