Question

From a disc of mass $2kg$ and radius $44m$ small disc of radius $1m$ with center $O$ is extracted. The new moment of inertia about an axis passing through $O$ perpendicular to plane of disc is

• A. $16kg{m}^2$
• B. $12kg{m}^2$
• C. $\frac{255}{16}kg{m}^2$
• D. $\frac{247}{16}kg{m}^2$

Answer 1

The correct option is B $12kg{m}^2$

APPLY II axis theorem, I removed $=\frac{1}{2\times 968}+\frac{4}{2\times 960}$

I remain $={\frac{1}{2}}^{\left(2\right)}{\left(44\right)}^2-\frac{5}{2\times 968}=12kg{m}^2$