Question

Four particles each of mass $m$ are placed at the corners of a square of side length $l$. The moment of inertia of four bodies about an axis passing through the opposite corners of the frame is:

• A. $\sqrt{2}M{L}^2$
• B. $2M{L}^2$
• C. $M{L}^2$
• D. $2\sqrt{2}M{L}^2$

Answer 1

The correct option is C $M{L}^2$

Since we need to find out MI about a diagonal, the particles at the end of this diagonal will have zero contribution to MI.
$I_{diagonal}=2m(\frac{L}{\sqrt{2}}{)}^2$
$=m{L}^2.$