Question

Moment of inertia of a disc about diameter is $I$ . Find the moment of inertia of disc about an axis perpendicular to its plane and passing through its rim.

• A. $6I$
• B. $4I$
• C. $2I$
• D. $8I$

Answer 1

Answer: (A)

$6I$

Answer 2

Moment of inertia of a disc about a diameter is $\frac{1}{4} \, MR^{2}=I$ (given) $\therefore$ $MR^{2}=4I$ Now, required moment of inertia $=\frac{3}{2}MR^{2}$ $=\frac{3}{2}\left(4 I\right)=6I$