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 , Work is understood as the change in the state of motion of a body produced by a force of a given magnitude. Or what is the same, will be equivalent to the energy needed to move it in an accelerated way.
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 a Work increment, nor can it be symbolized by ΔW.
For the work to take place there must be an applied force, there must be a displacement due to its action , and the force must have a component along that displacement .
Calculating the work respond to various formulations by the mechanical classical relativistic or quantum .
Positive and negative work
Work 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, then, the applied force (with its respective direction) and the distance traveled by the moving body must be considered.
Hence, we can talk about two types of work: positive and negative.
- Positive work . It occurs when the applied force goes in the same direction as the displacement of the body, producing a positive acceleration .
- Negative work . It occurs when the force applied goes in the opposite direction to the displacement of the body, which can produce a negative acceleration or deceleration.
Similarly, 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 because he can lift a certain body faster than the child.
We measure the power in Watts (which corresponds to one Joule per second, that is to say a Joule is the work that is needed to produce a Watt of power in a second). We must also consider the concept of efficiency within physics, which refers to performance within a process and is obtained from the relationship between useful and inverted energy. The energy that is lost forms heat in the environment .
Energy is understood as the ability of a body or mass to carry out a job after being subjected to a force . It is understood that without energy it is not possible to perform a job.
The energy of a body is given by speed or by its position . That is why the potential energy that is the one that a body possesses when it is immobile from the kinetic energy is different when the body is set in motion, that is, it travels at a certain speed. The unit with which energy is measured (the same as work) is the Joule (or July) which represents the amount of energy needed to lift a kilogram of mass 10 cm from the earth’s surface. It is also possible to measure energy using calories (a Joule is the same as 0.24 calories).