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Question: Answered & Verified by Expert

A uniform ball of radius r rolls without slipping down from the top of a sphere of radius R. The spin angular velocity of the ball when it breaks away from the sphere is (Assume initial velocity negligible)

PhysicsRotational MotionJEE Main
Options:
  • A 1 0 g R + r 1 7 r 2
  • B 1 0 g R - r 1 7 r 2
  • C 1 0 g R + r 1 7
  • D

    1 0 R + r 17 r 2

Solution:
2648 Upvotes Verified Answer
The correct answer is: 1 0 g R + r 1 7 r 2
mv2R+r=mg cosθ; mgh=12mv2+12Iω2

mg R + r 1 - cos θ = 1 2 mv 2 + 1 5 mv 2 = 7 1 0 mv 2

         

1 0 7 mg 1 - cos θ = mg cos θ

mv 2 = 1 0 7 mg R + r 1 - cos θ 1 0 7 = 1 7 7 cos θ

or  cos θ = 1 0 1 7

v = g R + r cos θ = 1 0 1 7 g R + r

and ω = v r = 1 0 g R + r 1 7 r 2

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