Question

From a disc of radius R, a concentric circular portion of radius $r$ is cut out so as to leave an annular disc of mass M. The moment of inertia of this annular disc about the axis perpendicular to its plane and passing through its centre of gravity is.

• A. $\frac{1}{2}M(R^2+r^2)$
• B. $\frac{1}{2}M(R^2-r^2)$
• C. $\frac{1}{2}M(R^4+r^4)$
• D. $\frac{1}{2}{M}^{\prime }(R^4-r^4)$

Answer 1

The correct option is A $\frac{1}{2}M(R^2+r^2)$

The moment of inertia of this annular disc about the axis perpendicular to its plane will be $\frac{1}{2}M(R^2+r^2)$.