Question

A smooth chain of length $2 \,m$ is kept on a table such that its length of $60\, cm$ hangs freely from the edge of the table. The total mass of the chain is $4\, kg$. The work done in pulling the entire chain on the table is, (Take $g=10 \,m / s ^{2}$ )

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

Answer 1

Answer: (A)

Mass of the chain lying freely from the table $= M \frac{1}{ L }$
$
\begin{array}{l}
=4 kg \times \frac{0.6}{2} \\
=1.2 kg
\end{array}
$
The distance of center of mass of chain from the table $=\frac{1}{2} \times 0.6 m =0.3 m$ Thus the work done in pulling the chain $=m g h=1.2 \times 10 \times 0.3 J =3.6 J$