Originally Posted by sureshs
Once again confirms that the kick of the ball is not due to the topspin interaction with the ground, but the already higher point from which a topspin ball drops to the ground: "The steeper angle makes the bounce higher"
This does not confirm anything as it's saying just that. You're wanting to describe an incomplete picture with only half of the situation. In the other thread, I gave the example of dropping a ball from 8 feet straight up and down, say a lob into the service box. You could tee off on that without any difficulty. The reason the topspin serve is so nasty is not because of the steeper angle. It's because it has BOTH the steeper incident angle, and greater incident velocity due to the Magnus force. In other words, it is carrying extra momentum in its spin which, due to the ground, gets translated into a higher and more difficult bounce. The topspin serve takes a portion of its horizontal velocity (towards the opponent) and turns it into vertical velocity as the magnus effect forces the ball to the ground more quickly than gravity alone. No matter what the physics, if the ball bounces differently even though it looks the same, then something applied a force to something. In this case, the ball applied more force to the ground. The angle of incidence itself is simply a component of all of these interactions.