The radius of gyration about the polar axis of a circular lamina of radius 0.2 m is:

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RRB JE ME 22 Apr 2025 Shift 2 CBT 2 Official Paper

Answer 1

Concept:

The radius of gyration about the polar axis is given by:

\( k = \sqrt{\frac{J}{A}} \)

For a circular lamina:

Calculation:

\( k = \sqrt{\frac{\pi R^4 / 2}{\pi R^2}} = \sqrt{\frac{R^2}{2}} = \frac{R}{\sqrt{2}} \)

\( k = \frac{0.2}{\sqrt{2}} \approx 0.141~\text{m} \approx 0.14~\text{m} \)