Work can be done very quickly rather slowly; there can be difference rates at which work is done.
Power is the rate at which work is done or the work/time ratio. The equation for rate of doing work or power is:
The SI unit of power is the Watt. As implied by the equation for power, a unit of power is equivalent to a unit of work divided by a unit of time, that is, joule/second or J/s.
An Alternate Formula for Power
Work done is:
where is the force displacing an object by .
Combining the equations for work with that for power
Since the expression for velocity is
The expression for power can be rewritten as
This new equation for power shows that a powerful machines are both strong (i.e., large force) and/or fast (i.e., high velocity).