Question

A tennis ball traveling at 25.0 m/s has a mass of 58.5 g and bounces off a wall with a speed of 22.5 m/s. The impact took 3.33 ms. What is the magnitude of the average force exerted by the wall on the tennis ball? Assume the ball travels horizontally perpendicular to the wall both before and after it hits the wall.

Answer 1

Magnitude of average force is 751.52 N

Explanation:

By Newtons second law force is rate of change of momentum.

Initial momentum = Mass x initial velocity

Mass = 58.5 g = 0.0585 kg

Initial velocity = +25 m/s

Initial momentum = 0.0585 x 25 = 1.4625 kgm/s

Final momentum = Mass x Final velocity

Mass = 58.5 g = 0.0585 kg

Final velocity = -22.5 m/s

Final momentum = 0.0585 x -22.5 = -1.3163 kgm/s

Change of momentum = Initial momentum - Final momentum = 1.4625 - (-1.3163)

Change of momentum = 2.48 kgm/s

Time = 3.33 ms = 0.0033 s

$\texttt{Rate of change of momentum =}\frac{2.48}{0.0033}=751.52N$

Magnitude of average force is 751.52 N