The tendency of an object to return to its original shape after being changed by the outside pressure is called elasticity. In a rubber ball the rubber itself has some elasticity, but it is the pressure of the air inside the ball that is largely responsible for making it bounce. Thus a ball that has lost some of the air does not bounce so well. The size and weight of balls used in various types of sports have changed over a period of time. The rugby ball for example was made thinner so that it was easier to throw it.
Even the football last year was made smaller and lighter for fast play. When the ball is full of air, it hits the ground and flattens out. Then as it tries to get back in proper shape it pushes against the ground and rises.
Even the football last year was made smaller and lighter for fast play. When the ball is full of air, it hits the ground and flattens out. Then as it tries to get back in proper shape it pushes against the ground and rises.