Question

A ring of radius $0.5$ mass $10kg$ is rotating about its diameter with angular velocity of $20rad{s}^{-1}$. Its kinetic energy is :

• A. $10J$
• B. $100J$
• C. $500J$
• D. $250J$

Answer 1

The correct option is D $250J$

Moment of inertia of a ring about its diameter

$I=\frac{1}{2}m{r}^2$

and kinetic energy is given by

$E_K=\frac{1}{2}I{\omega }^2$

$E_k=\frac{1}{4}m{r}^2{\omega }^2$

$=\frac{1}{4}\times 10\times (0.5{)}^2\times (20{)}^2$

$=250J$