A tennis ball of mass is approaching a stationary racquet horizontally at (the…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A tennis ball of mass 58g is approaching a stationary racquet horizontally at 10ms−1 (the positive x–direction is defined to be the direction the ball is moving just before impact). While the ball is in contact with the strings, the magnitude of the net horizontal force exerted on the ball varies with time as follows:
• from t=0 to t=4ms the force increases uniformly from 0N to 600N
• from t=4ms to t=6ms the force remains constant at 600N
• from t=6ms to t=8ms the force decreases uniformly back to 0N
Assume no other horizontal forces act on the ball during this interval.
(a) Describe qualitatively how the impulse delivered to the ball builds up during each of the three time intervals indicated above.
(b) Identify the direction of the total impulse on the ball and relate it to the direction of the ball’s initial momentum.
(c) Explain how a comparison of the magnitudes of the total impulse and the ball’s initial momentum indicates whether or not the ball reverses direction after leaving the racquet.
(d) Without performing any explicit calculations, rank the magnitudes of the impulses delivered during the three individual time intervals and justify your ranking.