Physics - Center of Mass Question with Solution | TestHub

PhysicsCenter of MassMiscellaneousEasy2 minPYQ_2020
PhysicsEasysingle choice

As shown in the figure, a chain of massmis placed on a smooth quarter circular portion of radiusR. EndA is tied with a wedge while the remaining chain is free, then the minimum work required to be done by the external agent to make the chain horizontal keeping pointAfixed, is

Options:

Answer:
B
Solution:

Center of mass of the chain is at 2R π from horizontal

As shown in figure .......

Height gain by center of mass is 2 R π





Wg=-mg2Rπ

Wext.=-Wg=mg2Rπ

Alternate solution





U i = ∫ - dm gy

=g∫R cosθmπ2dθ

=-2Rgmπ∫0π2cosθdθ

=-2Rgmπ[sinθ]0π/2

=-2mgRπ

Uf=0⇒ΔU=wext=2mgRπ

Stream:JEESubject:PhysicsTopic:Center of MassSubtopic:Miscellaneous
⏱ 2mℹ️ Source: PYQ_2020

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