Question

Two metallic discs have same mass and same thickness but different densities. The moment of inertia about the geometrical axis will be more of the disc :

• A. with lower density.
• B. with higher density.
• C. moment of inertia of both the discs will be same.
• D. nothing can be said.

Answer 1

The correct option is A with lower density.

Both the disc have same mass and same thickness. The one with the lower density will have larger radius. Thus using the relation $I=\frac{m{r}^2}{2}$ the disc with lower density and hence larger radius will have higher moment of inertia.