momentum and impulse?

Question

Question About Momentum and impulse?
A tennis player swings her 1000 g racket with a speed of 13.0 . She hits a 60 g tennis ball that was approaching her at a speed of 17.0 . The ball rebounds at 45.0 .

1)How fast is her racket moving immediately after the impact? You can ignore the interaction of the racket with her hand for the brief duration of the collision.


2)If the tennis ball and racket are in contact for 13.0 , what is the average force that the racket exerts on the ball?

Answer 1

Conservation of momentum gives the first answer. The sum of the products of the individual masses times their velocities before collision will be equal to that after. You must take into account the direction of the velocities also. Take positive as the direction of motion of the racket. So 1000*13 - 60*17 = 45*60 + v*1000. solve for v. v = (1000*13 - 60*17 - 45&60)/1000. If the result is positive, the racket continues moving in its initial direction.

The change in momentum of the ball is equal to the impulse from the racket. Impulse is force times time. The change in ball momentum is 45*60 + 17*60 (final momentum minus initial momentum).