## University Physics with Modern Physics (14th Edition)

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.