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JEE Main2014PhysicsRotational MotionActual

A bob of mass m attached to an inextensible string of length l ⁡ is suspended from a vertical support. The bob rotates in a horizontal circle with an angular speed ω rad/s about the vertical. About the point of suspension :

Options

  1. AAngular momentum is conserved
  2. BAngular momentum changes in magnitude but not in direction
  3. CAngular momentum changes in direction but not in magnitude
  4. DAngular momentum changes both in direction and magnitude

Correct answer

C. Angular momentum changes in direction but not in magnitude

Step-by-step solution

τ = mg × l sin θ . (Direction parallel to plane of rotation of particle) as τ is perpendicular to L → , direction of L changes but magnitude remains same.

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