Question

The moment of Inertia of a solid cylinder of mass '$M$' and radius $R$ about its Axis(as shown) is.

• A. $M{R}^2$
• B. $\frac{M{R}^2}{4}$
• C. $\frac{M{R}^2}{2}$
• D. $\frac{M{R}^2}{3}$

Answer 1

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

If we extrude the disc along the axis which is perpendicular to plane of disc and passing through its center we get a cylinder.
So, moment of inertia of disc of mass '$M$' and radius $R$ is same as that of cylinder of mass '$M$' and radius $R$ .
Moment of inertia of disc is $\frac{M{R}^2}{2}$ = Moment of inertia of cylinder

Point to remember:Moment of inertia of cylinder does not depends upon the length (i.e. $h$) of the cylinder.