A uniform chain of length 4m is kept on a table such that a length of 120 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 ?

Options

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

Answer

B

Explanation

Mass per unit length = `M/L = 4/2 = 2 kg//m`
The mass of 0.6 m of chain = `0.6 xx 2 = 1.2 kg`
The height of centre of mass of hanging part
`h = (0.6 + 0)/(2) = 0.3 m`
Hence, work done in pulling the chain on the table = Work done against gravity force i.e.,
`W = m gh`
`= 1.2 xx 10 xx 0.3 = 3.6 J`