Practice question
Question
A solid cylinder of mass 2kg and radius 0.1m rotates about its axis at 20rad/s. What is its rotational kinetic energy?
Explanation
I = 12MR2 = 12×2×(0.1)2 = 0.01kg m2. K = 12Iω2 = 12×0.01×(20)2 = 0.005×400 = 2J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 2.0 J. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.