Per NCERT §6.11 (frictionless rigid body), the work done by an external torque equals which?
AHeat dissipated
BLoss due to friction
CZero in steady rotation
DThe change in rotational KE
Answer & Solution
Correct answer: D. The change in rotational KE
NCERT §6.11: no internal motion, no friction ⇒ τω = d/dt((1/2)Iω²) ⇒ W_ext = ΔK_rot. Work-energy theorem in rotation.
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