Question

The M.I. of disc about an axis perpendicular to its plane and passing through its centre is $\frac{1}{2}M{R}^2$. Its M.I. about a tangent perpendicular to its plane will be

• A. $\frac{3}{2}M{R}^2$
• B. $\frac{1}{2}M{R}^2$
• C. $\frac{3}{4}M{R}^2$
• D. Cannot be determined

Answer 1

The correct option is A $\frac{3}{2}M{R}^2$

$I_{target}=I_{zc}+M{R}^2$

(Parallel axis theorem)

$I_{zc}=\frac{M{R}^2}{2}{I}_{target}=\frac{M{R}^2}{2}+M{R}^2=\frac{3}{2}M{R}^2$

Hence the correct answer is $=\frac{3}{2}M{R}^2$