Question

A metal square of mass M has a moment of inertia = I about an axis perpendicular to the plane of the lamina passing through the Centre of gravity. If the mass is reduced to half of its mass and the side of the square is reduced to a/3, what will be the new moment of inertia

• A. I/18
• B. No change in moment of inertia
• C. I/6
• D. I/2

Answer 1

The correct option is A I/18

Moment of inertia for a square plate is given by $\frac{M{a}^2}{6}$
If new mass is M/2 and $a^{\prime }=a/3$
Substituting, we get $I^{\prime }=\frac{M{a}^2}{18\times 6}=I/18$