You'd be surprised what happens when you hit the ball. So many elements of physics occur when you hit the ball. The more you understand the physics of tennis, the better off you'll be. If you understand how coefficients of friction work, how velocity and acceleration work, how Bernoulli's Principle works, you would understand the game so much better.
Why do you think flat tennis balls cannot be hit as hard as newer balls? Flat balls have increased impact times with the string bed. The increased impact time reduces the effect that the force of a tennis racquet has on the ball. So no matter how hard you hit the ball, your maximum velocity will always be decreased the longer you use tennis balls. The same applies to the force the ground imparts on a tennis ball. The collision time is increased, reducing the effect the tennis ball has on the ground, thus reducing the return effect from the ground, resulting in lower bounces and shorter bounces.
Like I said, if you learn the physics of the game, you'd have a better understanding of how to manipulate these factors in your favor. It's one thing to know something works. It's another to know HOW something works.
