A car engine is an example of a machine that is given a power rating. Thus, the power of a machine is the work/time ratio for that particular machine. The power rating indicates the rate at which that machine can do work upon other objects. All machines are typically described by a power rating. Most machines are designed and built to do work on objects. One horsepower is equivalent to approximately 750 Watts. For historical reasons, the horsepower is occasionally used to describe the power delivered by a machine. Thus, a Watt is equivalent to a Joule/second. As is implied by the equation for power, a unit of power is equivalent to a unit of work divided by a unit of time. The standard metric unit of power is the Watt. Mathematically, it is computed using the following equation. The hiker has a greater power rating than the rock climber.

The quantity that has to do with the rate at which a certain amount of work is done is known as the power.

The two people might do the same amount of work, yet the hiker does the work in considerably less time than the rock climber. On the other hand, a trail hiker (who selects the easier path up the mountain) might elevate her body a few meters in a short amount of time. For example, a rock climber takes an abnormally long time to elevate her body up a few meters along the side of a cliff. Sometimes, the work is done very quickly and other times the work is done rather slowly. Work has nothing to do with the amount of time that this force acts to cause the displacement. The quantity work has to do with a force causing a displacement.

Power on time