Answer: 13MR²/32.
- A 13MR²/32
- B MR²/2
- C 15MR²/32
- D 3MR²/8
Correct answer: A. 13MR²/32
Explanation: Mass of hole = M/4 (proportional to area R²/4). I<sub>hole</sub> about disk centre = (1/2)(M/4)(R/2)² + (M/4)(R/2)² = MR²/32 + MR²/16 = 3MR²/32. I<sub>new</sub> = MR²/2 - 3MR²/32 = 13MR²/32.
Torque about axis O equals the force F multiplied by the perpendicular distance r⊥ from the axis to the line of action of the force, producing rotation.
Concept context
Moment of inertia, torque, angular momentum, rolling motion. Very high JEE weightage.
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