A hoop and a disc have the same mass and radius and rotate at the same angular speed. How are their rotational kinetic energies related?
Correct answer A. K.E. of hoop = 2 × K.E. of disc
Explanation
Rotational K.E. is ½Iω²; a hoop has I = MR² while a disc has I = ½MR², so at the same ω the hoop has twice the kinetic energy.
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