Practice question
Question
A thin ring of mass 4kg and radius 0.3m rotates about its center at 8rad/s. What is its rotational kinetic energy?
Explanation
I = MR2 = 4×(0.3)2 = 0.36kg m2. K = 12Iω2 = 12×0.36×(8)2 = 0.18×64 = 11.52J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 11.52 J. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.
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