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. `sqrt(24)`
B. `sqrt(32)`
C. `sqrt(18)`
D. `sqrt(9)`

Answer

C

Explanation

`E = 12 xx 75 % = 12 xx 75/100 = 9 J `
`1/2mv^(2) = E `
`u = sqrt((2E)/m) = sqrt((2xx9)/1 ) = sqrt(18)` m/s