Question

A machine that operates a kiddie ride at an amusement park requires 2500 J to lift a 30.0-kg child 5.0 meters. What is the efficiency of this machine?

Answer 1

The work is given by the formula:

$$W=mgh=(30)(10)(5)=1500 J$$

The efficiency of this machine:

$$\eta = \frac{1500}{2500}=0.6$$

or 60%.