Question

The moment of inertia of a solid disc made of thin metal of radius $R$ and mass $M $ about one of its diameters is given by $\frac{MR^{2}}{4}$. What will be the moment of inertia about this axis, if the disc is folded in half about this diameter?

• A. $\frac{MR^{2}}{8}$
• B. $\frac{MR^{2}}{2}$
• C. $\frac{MR^{2}}{4}$
• D. $MR^{2}$

Answer 1

Answer: (C)

As mass distribution in rotation about the diameter is same in both cases, moment of inertia also remains same in both cases.
$\therefore $ Moment of inertia (half folded disc)$=\frac{MR^{2}}{4}$