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Question: Answered & Verified by Expert
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 :
PhysicsRotational MotionJEE MainJEE Main 2014 (06 Apr)
Options:
  • A Angular momentum is conserved
  • B Angular momentum changes in magnitude but not in direction
  • C Angular momentum changes in direction but not in magnitude
  • D Angular momentum changes both in direction and magnitude
Solution:
1971 Upvotes Verified Answer
The correct answer is: Angular momentum changes in direction but not in magnitude
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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