Practice question
Question
A hollow cylinder of mass 5kg and radius 0.2m rotates about its axis at 10rad/s. What is its rotational kinetic energy?
Explanation
I = MR2 = 5×(0.2)2 = 0.2kg m2. K = 12Iω2 = 12×0.2×(10)2 = 0.1×100 = 10J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 10 J. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.