That tennis ball calculation is wrong, He forgot to square the 55.55 m/sec/sec. Plus, he does not account for the time the racket spends pushing the ball in a powering through stroke. Others suggest the ball was in contact with the racket for 48 cms. As he said, he did not stay at a Holiday Inn Express nor is he a physics expert. If the ball was in contact for only a short distance, the 2200 G's would be the answer. At 48 cms of contact with the racket, the G's would be 320.

The ball that hit you was not going 200 km/hr (55 m/sec). A common tennis serve is 34 m/sec as the ball leaves the racket. By the time it crosses the net, it has lost a lot of speed, maybe to 25 m/sec.

At 58 grams, the tennis ball does not have much effect on a 5000 gram human head attached to a heavier body. According to my calculations, a 5000 gram head would move only about 5 inches when struck by 58 grams at 25 m/sec. The G's of that hit would be about 50 or maybe a bit more. It would move less if there was an effort to limit any movement. In that case, the G force would be higher. Sounds like enough G's for a concussion.

The numbers in the braininjury.com web site are not supported by either research or common physics. It would take quite a plop to get 10 G's. It would take a 20 inch fall with only 2 inches of cushion distortion to get 10 G's. I don't know of many butts that are 20 inches higher than the seat of an easy chair with only 2 inches of cushion distortion. Mine distorts about 4 inches. This site is an attorney's web site with a lot of 'selling to the jury.'