The mass of a regulation tennis ball is 52.0 g (although it can vary slightly),

Question

The mass of a regulation tennis ball is 52.0 g (although it can vary slightly), and tests have shown that the ball is in contact with the tennis racket for 35.0 ms . (This number can also vary, depending on the racket and swing.) We assume a 35.0 ms contact time in this problem. In the 2011 Davis Cup competition, Ivo Karlovic made one of the fastest recorded serves in history, which was clocked at 156 mi/h (70 m/s).

What impulse and what average force did Karlovic exert on the tennis ball in his record serve?

Express your answer to two significant figures.

What average force did Karlovic exert on the tennis ball in his record serve?

Express your answer to two significant figures.

F= ____ N

Explanation / Answer

Mass m = 52.0 x 10-3 kg

Time for which the ball in in contact with racket, t =35.0 ms = 35.0 x 103 s

Initial velocity Vi =0m/s

Final velocity Vf = 70 m/s

Impulse = change in momentum = m ( Vf - Vi ) = 52.0 x 10-3 x 70 = 3.64 kg.m/s

Average force = (change in momentum ) / time = 3.64 / (35 x 10-3 )= 104 N

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