E1.5 Work, Energy and Power (Power):

If work is done faster, power is higher. If work is done slower, power is smaller.

Power is the rate at which work is done. It is also called the energy is transferred in a unit of time. If work is done faster, power is higher. If work is done slower, power is smaller. For example:

In the race between the tortoise and the rabbit, the rabbit has more power and accelerated faster. But the tortoise did the same work and covered the same distance in a much longer time. The tortoise showed less power.

Mathematically,

Power is defined as the rate at which the work is done.

$Power\;(P) = \frac{Work\; done}{time\; taken} = \frac{W}{t}$ .......... (i) 

or, 

$Power\;(P) = \frac{W}{t} = \frac{\vec{F}.\;\vec{s}}{t} = \vec{F}.\vec{v}$ .......... (ii)

Where, $F$ = Force and $v$ = velocity.

Thus, power of an agent measures how fast it can do the work. It is a scalar quantity (having no direction). In SI system, the unit of power is Joule / Second ($J/S$) or Watt ($W$).

Another unit of power is horse-power ($h.p$). 1 h.p. = 746 Watt.

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