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NEET 2024 · Moment of Inertia & Radius of Gyration

Moment of Inertia & Radius of Gyration question from NEET 2024

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Moment of Inertia & Radius of Gyration

The radius of gyration of a solid sphere of mass 5 kg5\text{ kg} about XYXY is 5 m5\text{ m} as shown in figure. The radius of the sphere is 5x7 m\frac{5x}{\sqrt{7}}\text{ m}, then the value of xx is:

Figure

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Answer: (d)

  1. XY is a tangent: I=25MR2+MR2=75MR2=MK2I = \frac{2}{5}MR^2 + MR^2 = \frac{7}{5}MR^2 = MK^2.
  2. 75R2=25⇒R=557 m\frac{7}{5}R^2 = 25 \Rightarrow R = \frac{5\sqrt{5}}{\sqrt{7}}\text{ m}
  3. Comparing with 5x7\frac{5x}{\sqrt{7}}, x=5x = \sqrt{5}.
  4. So the answer is (d) 5\sqrt{5}.
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