Originally Posted by t135
Momentum from the stroke takes you off the ground.
No it doesn't. This is a commonly repeated tennis myth. Your arm and the racket do not have enough mass to lift you off the ground from momentum.
The only momentum that will lift you off the ground during the stroke is that developed in your body because your feet are pushing you off the ground. In every other sport this is called hopping or jumping, but because so many tennis players have been told not to jump, they mention some sort of mythical momentum which is lifting them into the air.