Question

A disc of moment of inertia of a body about s given axis 15kgm^2 rotates constantly about the centre with an angular velocity of 20rads^-1. find its rotational energy and its angular momentum about the centre

Answer 1

Denote $I$ - moment of inertia and $\omega$ -angular velocity.

Then rotational energy is

$$E=\frac{I\omega^2}{2}=\frac{15\times20^2}{2}=3000 J$$

and angular momentum is

$$L=I\omega=20\times 15=300 \frac{kg\times m}{s}$$