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An object of mass m is tied to a string ...

An object of mass `m` is tied to a string of length `l` and a variable force F is applied on it which brings the string gradually at angle thit `theta` with the vertical. Find the work done by the force `F`
.

A

mg(`1-sin theta`)

B

mgL

C

mgL (`1-cos theta`)

D

mgL ( `1+cos theta`)

Text Solution

Verified by Experts

The correct Answer is:
C
Work done by the external force `=DeltaE` of the system (object)
`=DeltaPE( :.DeltaKE=0)=mgh=mg(L-L cos theta)=mgL(1-cos theta)`.
Hence (C) is correct.
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