Originally Posted by bhupaes
I understand, and you are right in the large picture. But we are applying the rules differentially, as when solving a problem in numerical analysis, by dividing time into very small segments.
Then you are saying the velocity is constant almost at collision, even if the racket was accelerating before? Then toly's point would be that the person applies no force, and of course he doesn't, because we just made the acceleration 0. That would be true for anything! If we say we will go by a boxer's hand's final speed only, we can claim that the boxer did not do anything at the instant of impact!
What use is that?