A tennis player receives a shot with the ball(0.0600 kg) travelling horizontally at 54.0 m/s and returns theshot with the ball travelling horizontally at 36.0 m/s in theopposite direction. (Assume the inital direction of the ball is inthe -x direction.) (a) What is the impulse delivered to the ballby the racket? (b) What work does the racket do on theball? A tennis player receives a shot with the ball(0.0600 kg) travelling horizontally at 54.0 m/s and returns theshot with the ball travelling horizontally at 36.0 m/s in theopposite direction. (Assume the inital direction of the ball is inthe -x direction.) (a) What is the impulse delivered to the ballby the racket? (b) What work does the racket do on theball?
Explanation / Answer
a) Impulse I can be defined by: I = m*v In this case, v = 54+36 = 90 m/s ( the ball isslowed from 54 m/s towards the player, to zero, and thenaccelerated to 36 m/s AWAY from the player. The total changeis the sum of the initial velocity towards and the final velocityaway) b) Work is the change in kinetic energy. W = KE = (1/2m*v2) The only thing that changed was v2 so KE = 1/2*m*(v2) =.5*.06*(90)2 = ? so KE = 1/2*m*(v2) =.5*.06*(90)2 = ?