Question

The moment of inertia of a circular disc about its own axis is $4kg{m}^2$. Its moment of inertia about the diameter will be

• A. $4kg{m}^2$
• B. $2kg{m}^2$
• C. $Zero$
• D. $8kg{m}^2$

Answer 1

The correct option is B $2kg{m}^2$

Let the moment of inertia about any of the two perpendicular axes passing through the diametral plane be $I$. Thus using perpendicular axis theorem we get $2I=\frac{M{R}^2}{2}$or $I=\frac{M{R}^2}{4}$ which is half the original moment of inertia. Thus correct option is B.