We explain what kinetic energy is. Also, the difference between potential energy and kinetic energy, and some examples.

## What is kinetic energy?

Kinetic energy is that energy that** possesses a body or system due to its movement**.

Physics defines it as the amount of work done by all the forces acting on a body with a given mass, necessary to accelerate it from an initial velocity to another final velocity. Once this speed is reached, according to the Law of inertia, the amount of accumulated kinetic energy will remain constant, that is, it will not vary, unless another force acts on the body again, exerting work on it, changing its speed and, therefore, its kinetic energy.

kinetic energy **often represented by the symbol AND_{c}** (can be E

_{+}or E

_{–}depending on the case), although sometimes the symbols are also used

*T*either

*K*. It is usually expressed in Joules (J).

It is possible to determine the kinetic energy of an object using various formulas in classical mechanics, such as: E_{c }= (mv^{2}) / 2 where *m* is the mass (Kg) of the object and *v* its speed (m/s). Thus, 1 J = 1Kg.1m^{2}/s^{2}.

Kinetic, like any other type of energy, can be converted into heat and other forms of energy.

See also: Electrical energy

## Kinetic energy according to the phenomenon of study

The study of kinetic energy depends on the theoretical framework required by the phenomenon to be analyzed:

**In classical mechanics**Kinetic energy depends on the mass and speed of the body, which will always be much less than the speed of light.**In relativistic mechanics**Phenomena are studied in which the speed of the object (*v*) is close to the speed of light, (which in physics is denoted by the letter*c*). In these cases, the kinetic energy formula is different from the classical case since in particular, this energy depends on the relationship*v/c.***In quantum mechanics**Events that involve subatomic particles such as electrons are described. It is a theory with a high degree of complexity, where physical quantities (including kinetic energy) are described with wave functions, which represent probabilities.

## Difference between potential energy and kinetic energy

The kinetic energy (E_{c}) and potential energy (E_{p}), added, **make up the mechanical energy (E _{m})**

**of an object or system**. However, they are distinguished in that while the first concerns bodies in motion, the second has to do with the amount of energy accumulated within an object at rest.

In other words, potential energy depends on how the object or system is positioned with respect to the field of forces around it, while kinetic energy has to do with the movements it undertakes.

There are three types of potential energy:

**Gravitational potential energy**It is linked to the height at which the objects are and the attraction of gravity on them.**Elastic potential energy**It has to do with the tendency of certain objects to recover their original shape, once they have been forced to abandon it by an external force (for example, springs).**Electrical potential energy**It is defined as the negative work done by the electrostatic force to move a charge from an initial position to a final position.

See more: Potential energy

## Examples of kinetic energy

Some examples where the existence of kinetic energy is confirmed can be:

**Throw a ball through the air**We apply force to a ball to throw it into the air, letting it fall due to gravity. By doing so, he will acquire kinetic energy that, when another player stops it, he will have to compensate with work of equal magnitude, if he wants to stop it and retain it.**A roller coaster car**The car of a roller coaster at an amusement park will have potential energy until the moment it begins to fall, and its speed and mass give it increasing kinetic energy. The latter will be greater if the car is full than if it is empty (since there will be greater mass).**Knock someone to the ground**If we run towards a friend and throw ourselves on him, the kinetic energy we gain during the race will overcome the inertia of his body and we will knock him down. In the fall, both bodies will add their joint kinetic energy and it will finally be the ground that stops the movement.