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Equal masses m each are placed at the corners of a square of side l. The moment of inertia of the system about an axis passing through one corner A and parallel to the diagonal BD is

Asked in JEE Main 16th March 1st Shift 2021 · Standard bodies and axis theorems

Answer: (4) 3ml²

Step-by-step solution

Place A at the origin with BD-parallel axis through A. The mass at A is on the axis (distance 0). The two adjacent corners are each at perpendicular distance l/(√2), and the opposite corner is at √2 l... measured to the axis it is at (2l)/(√2)=√2 l.

I=0+2 m(l/(√2))²+m(√2 l)²=ml²+2ml²=3ml².

Why the other options are wrong

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