Power is the rate at which energy is transferred, used or transformed. The unit of power is a joule per second (J/s), which is also known as a watt. The more wattage the more power or electrical energy is used per unit time. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts.

The transfer of energy can be used to do work. Therefore, the power is the rate at which this work is performed. The same amount of work is done when carrying a load up a hill whether the person walks or runs. However, more power is expended during the running because the work is done in a shorter amount of time.

Power can be calculated using different variables in the equations below:

P_avg= ∆W/∆t

P= lim┬(∆t→0)〖∆W/∆t〗

W=PT

Mechanical power is the combination of forces and movement. Power is the product of a force on an object and the object’s velocity. Mechanical power also describes the time derivative of work. If a mechanical system has no losses than the input power must equal the output power.