A ball with small mass m2 placed on a ball with large mass m1. The bottom of the m1 is a height h above the ground and the bottom of the m2 is a height h + d above the ground. The balls are dropped. To what height does the m2 rebound?

Note. Please consider the balls are separated by a very small distance at the beginning, m1 is much larger than m2 and assume that the balls bounce elastically.

Solution.

Let’s start with the law of the conservation of energy in order to find the velocity of the balls just before the lower ball hits the ground.