Power

Power is the rate of doing work and can be expressed mathematically as:

Power (W) =work done (J)/time taken (s)=force (N) ×velocity (m/s)

The unit of power is the watt (W) where 1 watt equals work done at the rate of 1 J/s.

Example

A body of weight 5 kN is to be raised through a height of 15 m in 10 s. Calculate the power required.

Work done=force (weight) ×distance moved=5kN×15m=75 kNm=75 kJ

Power required=work done/time=75 kJ/10 s=7.5kW (assuming 100% efficiency).