A tennis ball initially moves with a velocity of 34.0 m/s horizontally to the ri
ID: 1322712 • Letter: A
Question
A tennis ball initially moves with a velocity of 34.0 m/s horizontally to the right. A tennis racket strikes the ball, giving it a velocity of 34.0 m/s to the left. Treat the collision as elastic and the ball and racket as particles of mass 0.0570 kg and 0.263 kg respectively.
(a) Does the speed of the racket change as a result of the collision?
(b) What is the value of the total momentum of the system?
(c) Find the initial velocity of the racket.
to the left
Explanation / Answer
Take "to the right" to be positive and conserve momentum.
initial p = 0.0590kg * 34.0m/s + 0.270kg * u
final p = 0.0590kg * -34m/s + 0.270kg * v
where u, v are the pre- and post-collision speeds of the racket
For an elastic, head-on collision, we know (from CoE) that
the relative velocity of approach = relative velocity of separation, or
34m/s - u = v - -34m/s = v + 34m/s
v = -u ? plug this into the momentum equation: since initial p = final p,
0.0590kg * 34.0m/s + 0.270kg * u = 0.0590kg * -34m/s + 0.270kg * -u
2.006kg
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