1.

A uniform chain has a mass m and length l . It is held on a frictionless table with one - sixth of its length hanging over the edge. The work done in just pulling the hanging part back on the table is :A. `mgl/72`B. `(mgl)/(36)`C. `(mgl)/(12)`D. `(mgl)/(6)`

Answer» [1]
Weight of overhanging part of chain `=(mg)/(6)`
The weight acts at the centre of gravity of the overhanging part,
i.e., `(l)/(12)`below the surface of table .
Gain in potential energy `=(mg)/(6)xx(l)/(12)=(mgl)/(72)`
` :.` Work done = gain in potential energy `=(mgl)/(72)`


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