Topspin for a tennis ball to not change velocity while bouncing

1. The problem statement, all variables and given/known data

2. Relevant equations

Tangential v = wr

3. The attempt at a solution
I first drew a force diagram for when the ball contacts the floor.

Topspin means the ball is moving tangentially backward.
Therefore, the bottom moves at v – wR. Friction works opposite in the direction of motion, so it will slow it down if v > wR, but it will speed it up if v < wR. Therefore, in order for there to be no change, v = wR, so w = v/R

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