Practice question
Question
A thin ring of mass 1kg and radius 0.2m rotates about its center. If its kinetic energy is 4J, what is its angular speed?
Explanation
KE: K = 12Iω2. For a ring: I = MR2 = 1×(0.2)2 = 0.04kg m2. 4 = 12×0.04×ω2⇒8 = 0.04ω2⇒ω2 = 200⇒ω = 200≈14.14rad/s. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 14 rad/s. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.