Question

A uniform chain of length $l$ and mass $m$ is placed on a smooth table with one-fourth of its length hanging over the edge. The work that has to be done to pull the whole chain back onto the table is

• A. $\frac{1}{4}mgl$
• B. $\frac{1}{6}mgl$
• C. $\frac{1}{72}mgl$
• D. $\frac{1}{36}mgl$

Answer 1

Answer: (D)

$\frac{1}{36}mgl$

Weight of chain to be lifted $=\frac{mg}{4}$
Height through which centre of gravity is raised $=\frac{l}{8}$
Work done $=\frac{mg}{4}\times \frac{l}{8}=\frac{mgl}{32}$.