Question

1. A 2kg phonograph turntable with diameter 1.5m initially rotating at 4.5 rads makes 4 complete rotations before coming to a stop.

a) What is its angular acceleration

Answer 1

The angular acceleration is

$$\alpha=\frac{\omega^2}{2\phi}=\frac{4.5^2}{2·(4·2\pi)}=0.4\text{ rad/s}^{-1}.$$