PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
Abdul is playing a game of lawn tennis. When he serves, he tries to hit the ball from a height of 2.5 m. He wants the ball to travel 18.2 m horizontally before landing on the other side of the net. The net is 0.91 m high at its lowest point and is 11.9 m from Abdul.
Assume that the tennis ball travels horizontally from Abdul's racket, and there are no effects due to air friction. Use g=10 ms−2 .
In fact, according to the Lawn Tennis Association, the tennis ball may leave a server's racket at a speed of up to 230 km hr−1 .
(1) Show that the time it takes for an object to fall, from rest, a distance of 2.5 m is 0.707 s.
(2) What does this suggest the initial horizontal speed of the tennis ball to be as it leaves Abdul's racket?
(3) How much time will the tennis ball have taken to reach the net?
(4) Show that the tennis ball will pass over the net.
(5) Calculate the (faster) speed of the tennis ball in ms−1 .
(6) How much time would this serve take for the ball to travel 18.2 m from the server?
(7) Is the time you calculated in part f sufficient for the ball to travel the vertical distance of 2.5 m in order to land in the serving box on the other side of the net?
(8) Suggest how a real serve in a tennis game differs from Abdul's 'ideal' serve described in this question. Outline what the effects of any differences are.