Question

A machine lifts an object of weight 1.5 x 103 N to a height of 10 m. The machine has an overall efficiency of 20%. The work done by the machine in raising the object is: (Ans: D)

A. 3.0 x 103 J

B. 1.2 x 104 J

C. 1.8 x 104 J

D. 7.5 x 104 J 

Answer 1

$A=\frac 1\eta Fh=7.5\cdot 10^4~N.$