Drop a basketball and a tennis ball (with the tennis ball on top). The tennis ball will bounce higher than the original point of release! Why? Consider the basketball to have an elastic collision with the floor. At that instant, it is now traveling upward with essentially the same speed as the basketball and tennis ball were traveling downward a moment before. The basketball going up collides with the tennis ball going down, giving the dramatic result. Be careful! The ball can bounce in random directions!