question_answer

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 mass of the chain is 4kg. What is the work done in pulling the entire chain on the table       [AIEEE 2004]

A)             7.2 J   

B)             3.6 J   

C)             120 J  

D)             1200 J

Correct Answer: B

Solution :

                Fraction of length of the chain hanging from the table             \[=\frac{1}{n}=\frac{60cm}{200cm}=\frac{3}{10}\]Þ \[n=\frac{10}{3}\]             Work done in pulling the chain on the table             \[W=\frac{mgL}{2{{n}^{2}}}\]             \[=\frac{4\times 10\times 2}{2\times {{(10/3)}^{2}}}=3.6J\]