Question

A machine is 75$\%$ efficient’. What do you understand by this statement?

Answer 1

The ratio of useful work done by the machine to the work put into the machine by effort is called efficiency of the machine
$Efficiency=\frac{Workoutputonload}{Workinputbyeffort}$
$\eta =\frac{Workoutput}{Workinput}$$\times 100$
A machine is 75% efficient means, 75% of the work input to the machine is obtained as useful work. 25% of the work input is wasted in overcoming the friction.