Tennis racket theorem

The Tennis Racket Theorem says that if you take a tennis racket and wrap it in cling-film (plastic wrap) and then hit a tennis ball with it, the ball travels further than if you hit it with an normal, unwrapped racket. This is because the wrap on the racket allows air to move in and out of the strings, so it creates a sort of cushion of air around the ball and that makes it bounce further.