Power of a force

Transforming wind energy into electrical energy

In the world we live in, we can say that one of the most important physical concepts is energy , as it is present in practically everything we do on a daily basis. Energy is so important that even when we are resting our body needs it. We know that energy cannot be created or destroyed, but it can be transformed into other forms of energy. Depending on its source, we can classify it as mechanical, electrical, chemical, sound, luminous, nuclear, etc.

In our daily lives we usually use the word work , but this word is usually related to physical or mental effort, however, in Physics, this term represents the measurement of energy transformations.

The power of a force, on the other hand, represents the speed with which it does work, or even the speed with which energy is transformed into other forms of energy. For example, for a person to go up to the eighth floor of a building, he can use the elevator or the stairs. In both examples, stairs or elevator, the work performed will be the same, that is, the work of raising the body to the eighth floor.

But if that person makes use of the stairs, it will take longer to do the same job. In this way, we say that the power associated with the force performed by the body is less than that associated with the force of the elevator motor.

To determine the average power of a force, we must remember that it represents the work done, or the energy transformed, per unit of time. Therefore, we can write:


avg   is the average power of a force

τ is the work done

∆t is the variation of the time of action of the force

∆E is the transformed energy

In the SI, we measure these quantities with the following units:

P is given in watt (W)

τ or ∆E ​​is given in joules (J)

∆t is given in seconds (s)

We can also make a relationship between the power of a force and the magnitude of the force and the magnitude of the velocity of a body subjected to that force:

The work of a constant force is defined by:

Substituting II into I, we get:


We can write:

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