# What SI units are used to measure power?

Mar 28, 2014

The SI unit for power is the watt.

#### Explanation:

The watt (W) is the SI derived unit for power. It comes from the SI base units.

Velocity is the rate at which an object travels.

$v = \text{distance"/"time} = \frac{d}{t}$.

The units of velocity are metres per second (m/s).

Acceleration is the rate at which an object changes its velocity.

$a = \frac{v}{t}$.

The units of acceleration are metres per second squared ($\text{m·s"^"-2}$).

Force is any influence that tends to change the motion of an object. Force = mass × acceleration.

$f = m a$.

The newton (N) is the force needed to accelerate up a mass of 1 kg by $\text{1 m·s"^"-2}$.

$\text{1 N = 1 kg·m·s"^"-2}$

Work is the action of a force through a distance.

w = f × d.

The units of work are $\text{kg·m"^2"s"^"-2}$ or $\text{N·m}$.

Energy is the ability to do work. It has the same units as work. The SI unit for energy is the joule (J). $\text{1 J = 1 N·m}$.

Power is the measure of how much energy or work is used per unit time.

$\text{Power" = "energy"/"time}$

The SI unit of power is joules per second (J/s) or Watts (W).

In summary,

$\text{1 W = 1 J/s = 1 N·m/s = 1 kg·m"^2·"s"^"-3}$