Question

The moment of inertia of a circular disc of mass $200g$ and radius $5cm$ about a tangential axis normal to the plane of the disc will be :

• A. $750gc{m}^2$
• B. $7500gc{m}^2$
• C. $75gc{m}^2$
• D. $Zero$

Answer 1

The correct option is B $7500gc{m}^2$

The moment of inertia of solid disc about the center is $\frac{1}{2}m{r}^2$.
using parallel axis theorem we get the moment of inertia about the tangential axis as
$\frac{1}{2}m{r}^2+m{r}^2=\frac{3}{2}m{r}^2$
substituting the values we get
$\frac{3}{2}\times 200\times 5^2=7500gc{m}^2$