Mechanical power is power generated by machines like engines, muscles, levers or pulleys. It is distinct from other types of power, such as electrical or nuclear power, which are measured in different ways. To calculate the mechanical power involved in the interaction between two objects, you first need to calculate the work involved and how much time the interaction took. Power is defined as the work performed during a specific period of time and it is measured in horsepower (hp). Work is measured in foot-pounds (ft-lb) and is defined as the force exerted on an object multiplied by the distance the object is moved.
Identify the work done in the situation for which you are trying to calculate the mechanical power. For instance, suppose a mover uses a force of 45 pounds (lbs) to push a heavy box 8 feet (ft) across the floor of a truck. The work being done is the moving of the box.
Calculate the amount of work performed by multiplying the force used by the distance the object was moved. In the example:
Work = 45 lbs x 8 ft = 360 ft-lb
Divide the work performed by the time it took to perform it to calculate the mechanical power involved. Suppose that it took the mover 5 seconds (s) to push the box.
Mechanical power = 360 ft-lb / 5 s x (1 hp / 550 ft-lbs/second) = 0.13 hp
The mover exerted 0.13 horsepower of power when he moved the box across the floor of the truck.