Just out of curiosity, is there such a thing as a fast ball and a heavy ball? Or is a fast ball automatically a heavy ball, and vice versa? From my own experience, I do notice that there IS a distinction between a fast ball and a heavy ball. Although to be physically sound, a fast-paced ball will result in it feeling "heavy" on impact and to achieve this "heaviness," a ball must travel pretty fast in order to create this force at impact. Therefore, a fast ball and a heavy ball must be one and the same. However, it's not. I clearly see a difference and have tested this with several of my tennis partners. We didn't measure it with some sort of instrument in any ways, it was just off of how it feels on contact, so please keep that in mind. I have a partner who adopts the open-stance forehand(PARTNER1) and generates ball-pace through racket head acceleration, resulting in a fast topspin shot. I also have another partner who prefers the classic close-stance forehand(PARTNER2) and steps into his shot in order to generate pace and power; his shots are also fast and with topspin, just not as much topspin as my first partner but still a lot. The result? Although their ball-pace is fairly similar, the ball that was hit by my partner using the close-stance(PARTNER2) felt A LOT heavier and has quite a longer stretch. Now I know that by hitting a close-stance forehand, he's transferring his body weight into the ball as well, but the pace of his shots are still about the same as my other partner(PARTNER2) with the open-stance. I guess to sum it all up, what I'm asking is: why does PARTNER2's shot feel so much heavier than PARTNER1's shot, even though their shots are roughly at the same pace? The ball hit by PARTNER2 must have had more energy to release than the ball hit by PARTNER1, so why did it not travel significantly faster? Could I have been high when testing this out or something?