Estimated service speed (updated with vid, pg.3) For any of you physics majors out there-if some of my hardest serves can put brand new, fresh out of the can balls through the fence about 30-40% of the time and used balls about 70% of the time, about how fast is my serve? Note that I play at a half dozen different public courts and on average, that's about the percentage I've noticed when I hit 10 hard in a row. I think one of my hardest ever was when I blasted a used ball through the fence and it eventually came to a stop about 150 feet away on the surrounding grass. I'm pretty sure I can hit more than 110 mph, but hoping that I can exceed at least 120 mph. p.s. i've broken my strings 6 times this summer, 5 times on the serve, once on a groundstroke.