Answer
Find its moment of inertia.
Work Step by Step
Apply a known torque and measure the ball’s resulting angular acceleration. That gives the ball’s moment of inertia.
$$\Sigma \tau = I\alpha$$
$$I = \frac{\Sigma \tau }{\alpha }$$
Using Table 9.2, the moments of inertia of the 2 objects are:
$\frac{2}{5}MR^2$ for the solid sphere
$\frac{2}{3}MR^2$ for the hollow sphere
See which of these formulas better matches the ball’s moment of inertia, and you will know whether the ball is solid or hollow.
