IB Physics SL A.2.7 Friction and Resistive Forces

A student strikes a tennis ball that is initially at rest so that it leaves the racquet at a speed of $64 \mathrm{~m} \mathrm{~s}^{-1}$. The ball has a mass of 0.058 kg and the contact between the ball and the racquet lasts for 25 ms .

The student models the bounce of the tennis ball to predict the angle $\theta$ at which the ball leaves a surface of clay and a surface of grass.

The model assumes
- during contact with the surface the ball slides.
- the sliding time is the same for both surfaces.
- the sliding frictional force is greater for clay than grass.
- the normal reaction force is the same for both surfaces.
Predict for the student's model, without calculation, whether $\theta$ is greater for a clay surface or for a grass surface.