A block of mass 5 kg is raised from the bottom of the lake to a height of 3m without change in kinetic energy. If the density of the block is `3000 kg m^(-3)`, then the work done is equal to.

Options

A. `100 J`
B. `150 J`
C. `50 J`
D. `75 J`

Answer

A

Explanation

Upthrust =(Volume immersed ) (density of liquid) g
`=((5)/(3000))(1000)(10)`
`=(50)/3N`
weight =50 N`
`:.` Applied force (upwards) =weight-upthrust.
`=50-(50)/3 =(100)/3N`
`W =FS =(100)/3 xx 3`
`=100 J`