We explain what force is according to physics, how it is measured and what other concepts it involves. Positive and negative work. Energy and Power.

## What is work in physics?

In physics, it is understood by *job* to the **change in the state of motion of a body produced by a force** of a given magnitude or, what is the same, it will be equivalent to the energy necessary to move it in an accelerated manner.

It is a **scalar magnitude represented by the symbol W** (of *work*in English), expressed in units of energy, that is, in Joules (J) according to the International System. This is because it is basically a transit of energy and, for the same reason, it cannot be calculated as an increase in *job*nor can it be symbolized by ΔW.

So that he *job* occurs there must be a force applied,** a displacement resulting from their actions** and the force must have a component along said displacement.

The calculation of *job* will respond to various formulations from classical, relativistic or quantum mechanics.

See also: Lever

## Positive and negative work

He *job* occurs, for example, **when a man pushes a vehicle without fuel down the street** or when a hydraulic machine lifts a heavy wooden box. To calculate it, therefore, the applied force (with its respective direction) and the distance traveled by the moving body must be considered.

Hence we can speak of two types of work: positive and negative.

**positive work**. It occurs when the applied force goes in the same direction as the movement of the body, producing a positive acceleration.**Negative work**. It occurs when the applied force goes in the opposite direction to the movement of the body, and can produce a negative acceleration or deceleration.

## Power

Similarly, the power is **the relationship between the work done and the time it took to do it**. It is represented by the letter P and is measured in watts (1 watt = 1 J / sec.) and responds to the formula: P = W/Δt.

That is why, for example, an adult is more powerful than a child since he can lift a certain body with more force than the child.

We measure power in Watts (which corresponds to one Joule per second, that is, one Joule is the work needed to produce one Watt of power in one second). We must also consider the concept of efficiency within physics, which refers to the **performance within a process** and is obtained from the relationship between useful and invested energy. The energy that is lost forms heat in the environment.

Continue in: Power in physics

## Energy

Energy is understood as the capacity of a body or mass to** carrying out work after being subjected to force**. It is understood that without energy it is not possible to do work.

**The energy of a body is related to its speed or its position**. That is why potential energy, which is the energy possessed by a body when it is at a certain height with respect to a reference system, is differentiated from kinetic energy, which is the energy possessed by a body that is in motion.

The unit with which energy is measured (the same as work) is the Joule (or Joule). One Joule represents the amount of work done by a constant force of 1 Newton, over a distance of 1 meter in the same direction of the force.

Also** it is possible to measure energy using calories** (one Joule is the same as 0.24 calories).