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Kinetic and Potential Energy: Definition, Differences and Examples

Kinetic and potential energy: definition, differences and examples

Kinetic and potential energy are two types of energy that are interrelated in objects. Mechanical energy is the sum of the two types of energy. If there is no energy exchange with the outside, the mechanical energy is constant.

The unit of measurement for energy in the International System of Units is the Joule (J).

Kinetic and potential energies can be converted into many different types of energy. However, frequently both energies are combined with each other, it is very interesting for the calculation of the kinematics of an object.

What Is Kinetic Energy?

The kinetic energy is a form of energy that has a moving body because of inertia. This energy is equivalent to the work that needs to be done for the body to go from rest to the speed at which it is.

The kinetic energy is directly proportional to the mass and the square of the velocity.

In linear motion, the kinetic energy is determined by the formula

E c = (m·v 2 ) / 2

Where,

  • m is the mass (kg)

  • v is the speed with which the object is moving (m / s)

What Is Potential Energy?

The potential energy can be defined as the ability of an object to perform work because of the state in which the object is. This state can be the location in a force field or the internal configuration of the object.

Well known examples of potential energy are a:

  • An object in the Earth's gravitational field: At the Earth's surface, gravitational potential energy is determined by the formula E p = m · g · h. Where m is the mass (kg), g the gravitational constant (9.8 m / s) and h the height (m).

  • A charged particle in an electric field: in the reverse case, electric potential energy can be transformed into electric energy.

  • The energy of a tensioned spring: a compressed spring has elastic potential energy. The force exerted by the spring has the ability to do work.

Difference Between Potential and Kinetic Energy

Kinetic energy is related to the speed of a body. In physics, it corresponds to the work that must be supplied for an object that is stationary to acquire the speed it is carrying.

On the other hand, potential energy is the energy associated with a position. That is, the work that must be supplied to place an object in a certain position. For example, to raise an object to a certain height.

Examples Kinetic Energy and Potential Energy

Here are some examples where potential and kinetic energy are exchanged.

  1. The movement of a wagon on a roller coaster: When the wagon is at the highest point, the potential energy is maximum and it has no kinetic energy (speed 0). When it starts to go down, it loses height and gains speed, that is, the potential energy decreases, transforming itself into kinetic energy.

  2. The water in a river descends because the potential energy it has when it is at the top of the mountain is converted into kinetic energy. In this case, a large part of the energy is lost when rubbing against the stones of the river.

  3. The up and down movement of a ball thrown in the air.

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Published: May 8, 2019
Last review: December 17, 2021