Work Step by Step
The moral is not to ignore the vector nature of momentum and impulse. The ball and clay each have the same momentum just before they contact the door. The change in momentum of the ball is greater when it rebounds, compared to the clay’s change in momentum which is simply brought to a dead stop. The ball was not only brought to rest, but the greater impulse delivered to it reversed its momentum and sent it back the way it came. Each object delivers an impulse to the door that is equal and opposite to the impulse it received from the door. The superball delivers a greater impulse to the door, making it more effective for the task.