# What is kinetic energy?

## What Does Energía cinética Mean

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 a body or system possesses due to its movement .

The physical defined as the amount of work done by all forces acting on a body with a mass determined necessary to accelerate from an initial speed to another final speed. 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, hence its kinetic energy.

Kinetic energy is often represented by the symbol E c (it can be E + or E - , depending on the case), although the symbols T or K are sometimes used as well . 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 .

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

### Kinetic energy according to the study phenomenon

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

• In classical mechanics. The kinetic energy depends on the mass and the 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 v / c ratio .
• In quantum mechanics. Events involving 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 the potential energy (E p ), added together, make up the mechanical energy (E m ) of an object or system . However, they differ 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.

Said like this, potential energy depends on how the object or system is positioned with respect to the force field around it, while kinetics 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 regain their original shape, once they have been forced by an external force to abandon it (for example, springs).
• Electric 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 verified can be:

• Throw a ball through the air . We force a ball to throw it into the air, letting it fall due to gravity. In doing so, he will acquire kinetic energy which, when caught by another player, must compensate with work of equal magnitude if he wishes to stop and retain it.
• A roller coaster car. A roller coaster car in an amusement park will present 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 wagon is full than if it is empty (as there will be more mass).
• Knock someone to the ground . If we run towards a friend and jump on him, the kinetic energy that 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 the joint kinetic energy and it will finally be the ground that stops the movement.
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