BIO Human Biomechanics.? The fastest served tennis ball, served by “Big Bill” Tilden in 1931, was measured at 73.14 m/s. The mass of a tennis ball is 57 g, and the ball, which starts from rest, is typically in contact with the tennis racquet for 30.0 ms. Assuming constant acceleration, (a) what force did Big Bill’s tennis racquet exert on the ball if he hit it essentially horizontally? (b) Draw free-body diagrams of the ball during the serve and just after it moved free of the racquet.

Solution 42P Step 1: The acceleration at a particular instant, a = v/t Force, F = ma Step 2: a) In this problem, the change in velocity, v = 73.14 m/s Time of contact, t = 30 ms = 0.03 s 2 Therefore, the acceleration, a = 73.14 m/s / 0.03 s = 2438 m/s Mass of the tennis ball, m = 57 g = 0.057 kg Therefore, F = ma = 0.057 kg × 2438 m/s = 139 kg m/s = 139 N 2