Clay Ball vs. Rubber Ball

In class today, while doing the preliminary questions to the lab, we debated whether a clay or rubber ball, of equal mass, would push a door closed more. At first, I thought that the clay would close the door more; but, since the masses are equal, I rethought my intial response. The question is basically asking which medium will create the greatest impulse. Because the clay sticks to the door, the collision is inelastic, and energy is lost as the clay sticks to the door. Because the rubber ball bounces off the door, the collision is elastic. Kinetic energy is conserved for elastic collisions, and the change in velcoity is greater (impulse=m(change in velocity)). So, the impulse is greater with the rubber ball.

[ATTACH=CONFIG]508[/ATTACH]I found this picture online which helps to explain the elastic collsion in this problem.