Question

A tennis player receives a shot with the ball (0.0600 kg) traveling horizontally at 51.0 m/s and returns the shot with the ball traveling horizontally at 31.0 m/s in the opposite direction. (Take the direction of the ball's final velocity (toward the net) to be the +x-direction.)
(a) What is the impulse delivered to the ball by the racket?
magnitude N · s
direction

(b) What work does the racket do on the ball? (Indicate the direction with the sign of your answer.)
J

Answer 1

The impulse is the change of momentum
0.06 (31 - - 51) = .06(82) toward the net

It does negative work slowing the ball down and then positive work speeding it up.
[force opposite to motion then force in direction of motion]
-(1/2)(.06)(51)^2 +(1/2)(.06)(31)^2 ignoring losses due to compression etc
In other words the ball does work on the racket.