Question

A uniform chain of length $2m$ is kept on a table such that a length of $60cm$ hangs freely from the edge of the table. The total of the chain is $4kg$. What is the work done in pulling the entire chain on the table.

• A. $7.2J$
• B. $3.6J$
• C. $120J$
• D. $1200J$

Answer 1

The correct option is A $7.2J$

Mass $m=4kg$,Length $L=2m$ are the total mass and total length of the chain.

Let m and l be the mass and length of part of chain hanging down respectively.

$l=0.6m$

$\frac{M}{L}=\frac{m}{l}$

$m=\frac{l}{4}\times 4=\frac{0.6\times 4}{2}=1.2kg$

Tension in chain hanging down$=mg=1.2\times 9.8=11.76N$

Force required =Tension

Displacement=0.6m

Work=Force$\times$displacement

$=11.76\times 0.6=7.056J$