Potential energy

Potential energy is energy that is stored in an object. Potential energy takes on many forms. These forms include:

• gravitational potential energy
• elastic potential energy
• electrical potential energy
• chemical potential energy
• nuclear potential energy
• light energy

Gravitational potential energy

Gravitational potential energy is energy that is stored by an object in a gravitational field. An object raised into the air has the potential to gain kinetic energy through falling.

Gravitational potential energy can be expressed through the following formula:

GPE = mgh

where GPE is gravitational potential energy in joules (J), m is mass in kilograms (kg) and h is height in metres (m) and g is the acceleration due to gravity in metres per second per second (m/s²). On Earth, the average acceleration due to gravity is 9.8 m/s².

As can be seen from the formula, gravitational potential energy is directly proportional to the mass and height of the object in question. An object with a higher mass will have a higher gravitational potential energy than an object with a lower mass at the same height. Additionally, an object will have a higher gravitational potential energy if it is lifted higher in the gravitational field.

Gravitational potential energy also depends on where an object is located. Gravitational fields are weaker on some parts of the Earth (such as high in the mountains), so gravitational potential energy would be slightly lower at these points. Gravitational potential energy is different on planets other than Earth, too, since each planet has its own acceleration due to gravity.

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Elastic potential energy

Elastic potential energy is energy that is stored in an object when it is stretched or compressed. An example of an object with elastic potential energy is a rubber band that has been stretched out. If you were to stretch out a rubber band and then let go of it, the rubber band will release its energy by snapping back rapidly. Another example is a spring that has been compressed. If the spring is released, it will release its energy by snapping back into shape.

Elastic potential energy can be calculated with the following equation:

EPE = kx²

where EPE is elastic potential energy in joules and x is the length of extension or compression. The value of k is the spring constant, which is a number that represents the stiffness of the object. The stiffer the object, the harder it is to extend or compress. The higher the spring constant the stiffer the object.

Springs and other elastic objects can be used to store elastic potential energy to be converted later into kinetic energy. An example of this is a slingshot loaded with a small ball. When the rubber band in the slingshot is pulled back, it stores the energy used to pull it back as elastic potential energy. When the rubber band is released, the energy is released and transferred to the ball as kinetic energy.

An example of a compressed spring being used to transfer elastic potential energy into kinetic energy is a spring-loaded toy car. When the spring is compressed with the car in place, it stores elastic potential energy. When the spring is released, it transfers its energy to the car, which gains kinetic energy.

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Other forms of potential energy

Electrical potential energy is potential energy stored in an electrical field. When two positively charged particles (or two negatively charged particles) are brought close together, they are pushed apart from one another. Therefore, if two similarly-charged particles are forced together, they store potential energy. When the particles are released, they gain kinetic energy. This kind of potential energy can be seen by bringing the positive (or north) poles of a magnet close together.

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Chemical potential energy is potential energy stored in the bonds within molecules. Chemical potential energy is released through chemical change. Chemical potential energy is released in combustion reactions, for example, when oxygen combines with hydrocarbons to form carbon dioxide and water. Similarly, nuclear potential energy is potential energy stored in the bonds within atoms. When the bonds between atoms break, the nuclear potential energy is released. Some examples of this are nuclear power plants and atomic bombs. Chemical and nuclear potential energy are usually released as heat or light.