Tennis is a very popular sport in modern world. There are five grand slams and many tennis clubs around the world. The sport requires force. With the strings connect with the ball, for the ball to move a force needs to be applyed. This force sends the ball hopfuly over the net. The distace the ball travels depends on the spin of the ball. There is top spin, which makes the ball go over the net and then just drop to the ground. Then there is the back spin which when the ball bounces dosn't bouce forward bu slightly backwards. you never want to hit a ball flat because then the distace would be to great for the ball to stay in depending on the amount of force that you put behind the ball when hitting it. There you have the very basic physics of tennis.