Two iron solid discs of negligible thickness have radii R₁ and R₂ and moment of inertia I₁ and I₂, respectively. For R₂ = 2R₁, the ratio of I₁ and I₂ would be 1/x, where x = _______. Numerical answer type. Work it out, then open the answer.

Answer: 16. Same material and same (negligible) thickness: M ∝ R², so I ∝ R⁴. (I₁)/(I₂) = ((R₁)/(2R₁))⁴ = 1/16 So x = 16.

Two iron solid discs of negligible thickness have radii R₁ and R₂ and… | JEE Main 2025 (28 Jan, Shift 1)

Q57JEE Main 2025 · 28 JAN · SHIFT 1Medium

Moment of Inertia & Radius of Gyration

Two iron solid discs of negligible thickness have radii $R_1$ and $R_2$ and moment of inertia $I_1$ and $I_2$ , respectively. For $R_2 = 2R_1$ , the ratio of $I_1$ and $I_2$ would be $1/x$ , where $x =$ _______.

Numerical answer type. Work it out, then open the answer.

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Answer: 16

Same material and same (negligible) thickness: $M \propto R^2$ , so $I \propto R^4$ .
$\frac{I_1}{I_2} = \left(\frac{R_1}{2R_1}\right)^4 = \frac{1}{16}$
So $x = 16$ .

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