Question

A uniform chain of length $2m$ is kept on a table such that a length of $60cm$ hanging freely from the edge of the table. The total mass of the chain is $4kg$. The work done is pulling the entire chain on the table (Take $g=m{s}^{-2})$.

• A. $12.9J$
• B. $6.3J$
• C. $3.6J$
• D. $2.0J$

Answer 1

Answer: (C)

$3.6J$

Mass of length $2m$ of the chain $=4kg$
Mass of length $60cm$ or $0.60m$ of the chain
$=\frac{4\times 0.60}{2}=1.2kg$.
Weight of the hanging part of the chain
$=1.2\times 10=12N$
Since the centre of gravity of the hanging part lies at its mid point, i.e. $30cm$ or $0.30m$
$\therefore W=12\times 0.30=3.6J$.