Question

The efficiency of a machine is 60%, calculate the workdone by a man using this machine to raise a load of 250kg through a vertical distance of 2.5m(g=10ms-2)

Answer 1

$$\rm The\: efficiency=\frac{Output\:work}{Input\:work}$$

$$\eta=\frac{mgh}{W}$$

Hence, the work done by a man

$$W=\frac{mgh}{\eta}=\frac{250\times 10\times 2.5}{0.6}=10417\:\rm J$$

Answer: $10417\:\rm J$