That Federer serve is just one shot. Maybe it was a fault.
The question needs stats on successful serves.
Racket Head Motion During Impact - Also, given the racket motion, the time that the ball is in contact with the strings, say, 0.005 sec, is not necessarily negligible regarding the racket velocity. IRS, for example, takes only about 0.03 sec for the racket to be edge-on at about 90° to the forearm to β at impact. Tilt during contact?
How much is the racket tilting (closing) during those 0.005 seconds of ball contact? When during that time was the video frame captured?
Last edited by Chas Tennis; 01-30-2013 at 12:08 PM.