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Question: Answered & Verified by Expert
A small ring of mass m is constrained to slide along a horizontal wire fixed between two rigid supports. The ring is connected to a particle of same mass by an ideal string & the whole system is released from rest as shown in the figure. If the coefficient of friction between ring A and wire is 3 5, the ring will start sliding when the connecting string will make an angle θ with the vertical, then θ will be (particle is free to move and ring can slide only)

PhysicsLaws of MotionJEE Main
Options:
  • A 30o
  • B 45o
  • C 60o
  • D None of these
Solution:
1788 Upvotes Verified Answer
The correct answer is: 45o

Using energy conservation, we get

mgl cos θ = mv 2 2

mv2l=2mgcosθ

As the mass is moving in a circular motion, applying circular motion equation, 

T - mg cos θ = 2 mg cos θ

T = 3 mg cos θ

Tsinθ=μmg+Tcosθ

3 mg cos θ sin θ = μ mg + 3 mg cos 2 θ

θ = 4 5

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