I began to wonder something a week or two ago, watching Querrey against Nadal: Where does Querrey get his serve's power? He doesn't seem to even swing his racquet especially fast, but somehow he was serving up bombs consistently. It can't be that he's just using an 18 oz racquet or something. The question was repeated watching Henin v. Davenport today, that Davenport was really unloading on the ball and you could tell-- but it wasn't going that fast when all was said and done. Henin-Hardenne, though, would just coolly coil, uncoil, and the ball would fly across the court. How is it that the pros can hit the ball with such a small amount of effort-- for some of them, at least-- and have the speed be so high? The physics of it can't be different from amateurs, and I know Henin's not just plain built, so what gives?