A machine which is 75 percent efficient, uses 12 joules of energy in lifting up a 1 kg mass through a certain distance. The mass is then allowed to fall through that distance. The velocity at the end of its fall is (in `ms^(-1)`)

Options

A. `sqrt24`
B. `sqrt32`
C. `sqrt18`
D. `sqrt9`

Answer

C

Explanation

Potential energy of a body = 75% of 12 J
`mgh = 9 J rArr h=(9)/(1xx10)=0.9 m`
Now when this mass allow to fall then it acquire velocity
`v=sqrt(2gh)=sqrt(2xx10xx0.9)=sqrt(18)m//s`.