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MHT CET · Physics · Rotational Motion

A square lamina of side ' \(b\) ' has same mass as a disc of radius ' \(R\) ' the moment of inertia of the two objects about an axis perpendicular to the plane and passing through the centre is equal. The ratio \(\frac{\mathrm{b}}{\mathrm{R}}\) is

  1. A \(1:1\)
  2. B \(\sqrt{3}:1\)
  3. C \(\sqrt{6}:1\)
  4. D \(1:\sqrt{3}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\sqrt{3}:1\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \mathrm{I}_{\text {lamina }}=\frac{\mathrm{Mb}^2}{6} \\ & \mathrm{I}_{\text {disc }}=\frac{\mathrm{MR}^2}{2} \\ & \text { Given } \frac{\mathrm{Mb}^2}{6}=\frac{\mathrm{MR}^2}{2} \\ & \quad \frac{\mathrm{b}^2}{\mathrm{R}^2}=3 \\ & \therefore \quad \frac{\mathrm{b}}{\mathrm{R}}=\frac{\sqrt{3}}{1}\end{aligned}\)