Question

A tennis player player receives a shot with the ball (.06kg) travelling horizontally at 50.0 m/s and returns the shot with the ball travelling horizontally at 40.0 m/s in the opposite direction. a) What is the impulse delivered to the ball by the tennis racquet? b) What work does the racquet do on the ball?

Answer 1

Let:

m- 0.0600Kg
v1- +50.0 m/s
v2- -42 m/s

a)

momentum1 - momentum2 = impulse
p1 - p2 = Ft
m(v1 + v2) = Ft
Ft = 0.54 N-s

b)

Work is traditionally force times distance but an easy way to get through this one is to think logically and keep your units straight:

The racket creates an overall velocity of 90 m/s for the ball:

W=(Ft)*(V)
W=0.54 N-s * 90 m/s
W=48.6 N-m = 48.6 J