A boy holds a uniform chain of length 2,m which is kept on a smooth table such that a length of 60,c

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5.Work, Energy, Power and Collision

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A boy holds a uniform chain of length $2\,m$ which is kept on a smooth table such that a length of $60\,cm$ hangs freely from the edge of the table. The total mass of the chain is $4\,kg$. What is the work done in pulling the entire chain on the table .............. $\mathrm{J}$

A

$7.2$

B

$3.6$

C

$120$

D

$1200$

Solution

Fraction of length of the chain hanging from the

table $=\frac{1}{n}=\frac{60 \mathrm{cm}}{200 \mathrm{cm}}=\frac{3}{10} \Rightarrow \mathrm{n}=\frac{10}{3}$

Work done is pulling the chain on the table

$W=\frac{m g L}{2 n^{2}}=\frac{4 \times 10 \times 2}{2 \times(10 / 3)^{2}}=3.6 \mathrm{J}$

Standard 11

Physics

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