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The ratio of the radius of gyration of a hollow sphere to that of a solid cylinder of equal mass, for moment of inertia about their diameter axis AB as shown (cylinder radius R, length 2R, with AB at distance 2R from its centre), is √8/x. The value of x is ______.

Asked in JEE Main 5th April 1st Shift 2024 · Radius of gyration and numericals

Figure: Radius of gyration and numericals
Answer: 67

Step-by-step solution

Hollow sphere about a diameter: k₁²=2/3 R².

Cylinder about AB: I₂=(M(2R)²)/(12)+(MR²)/4+M(2R)²=(67)/(12)MR², so k₂²=(67)/(12)R².

(k₁²)/(k₂²)=(2/3)/(67/12)=8/(67), so x=67.

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