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Question: Answered & Verified by Expert

The toy-top (initially at rest) shown in the figure, has a moment of inertia 4×10-4 kg m2 and it is free to rotate about the stationary axis AA'. The string wrapped around the peg of the toy-top is pulled outwards without letting it slip and simultaneously maintaining a constant tension of 5.625 N. If ω is the angular speed (in rad s-1) of the top after 80 cm of string has been pulled off the peg, then mark your answer as ω100.

PhysicsRotational MotionJEE Main
Solution:
1469 Upvotes Verified Answer
The correct answer is: 1.50
Work done

=F×Δr=5.625×0.8m=4.5J and

work done =ΔK= 1 2 r 2 1 2 1 2

4.5= 1 2 ×4× 10 4 × ω r 2 0

... ( top starts from rest, ω i =0 )

ω f =150rad/s

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