A metal chain of mass 2 kg and length 90 cm over hangs a table with 60 cm on the table. How much work needs to be done to put the hanging part of the chain back on the table? (Let `g=10m//s^(2)`)

Options

A. 2 J
B. 10 J
C. 1 J
D. 3 J

Answer

C

Explanation

Given mass of metal chain m=2kg. Total length of chain `l=90cm=0.9m`
Hanging length of chain `l=90cm=0.9m`
`=30cm=0.3m`
The distance of centre of gravity of hangin length from the table,
`l_(e)=(l')/(2)=(0.3)/(2)=0.15m`
Mass of the hanging part of chain,
`m'=(0.30)/(0.90)xx2`
`m'=(2)/(3)kg`
`:.` Work needed to put hanging part of the chain back on the table,
`W=m'gl_(e)`
`=(2)/(3)xx10xx0.15=1J("":'g=10m//s^(2))`