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⚛️ Physics  ·  System of Particles and Rotational Motion  ·  NEET & JEE

A torque does zero work on a rotating body when the force is:

Answer: Directed toward the axis of rotation.

  • A Directed toward the axis of rotation
  • B Tangential to the path
  • C Along the angular displacement
  • D Perpendicular to the radius and in the plane of rotation

Correct answer: A. Directed toward the axis of rotation

Explanation: If force is directed toward the rotation axis (radial), it is perpendicular to displacement, so work = 0.

axis OPr⊥Fττ = r⊥ × F = r × F × sinθ

Torque about axis O equals the force F multiplied by the perpendicular distance r⊥ from the axis to the line of action of the force, producing rotation.

Concept context

Moment of inertia, torque, angular momentum, rolling motion. Very high JEE weightage.

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