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JEE Main 2020 (4 Sep, Shift 2) · Moment of Inertia & Radius of Gyration

Moment of Inertia & Radius of Gyration question from JEE Main 2020 (4 Sep, Shift 2)

Q149JEE Main 2020 · 4 SEP · SHIFT 2Medium

Moment of Inertia & Radius of Gyration

Consider two uniform discs of the same thickness and different radii R1 = R and R2 = $\alpha$ R made of the same material. If the ratio of their moments of inertia I1 and I2, respectively, about their axes is I1: I2 = 1: 16 then the value of $\alpha$ is:

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Answer: (b)

Same material and thickness: $M \propto R^2$ , so $I = \frac{MR^2}{2} \propto R^4$ .
$\alpha^4 = 16 \Rightarrow \alpha = 2$
So the answer is (b) 2.

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