Potential energy

Some things hold energy because of where they are.

A spring holds energy when you stretch it. This is called stored energy.

A ball holds energy when it is high up. This happens because of gravity. If the ball falls, it uses that energy to move.

Energy can also be held in other ways. It can be in tiny parts of an atom. It can even be in a bow.

People use bows to shoot arrows.

Scientists use a special name for this energy. They call it potential energy. It stays hidden until it is used.

This energy can help things work. It can help a machine throw a heavy weight. It can even keep planets in place.

Potential energy is energy that is stored because of an object's position.

It stays hidden until it is used to do work. An engineer named William Rankine first used this name in 1853.

There are many different kinds of potential energy. One kind is gravitational potential energy. This happens when you lift an object high up.

The higher the object, the more energy it holds. If you let it go, gravity pulls it down.

Another kind is elastic potential energy. This is stored in things like springs or bows.

When you stretch or squeeze them, they hold power. If you release them, the energy turns into movement.

There is also electric potential energy. This comes from electric charges. Even tiny parts of atoms hold energy. Scientists measure energy using a unit called the joule.

In space, gravity works on a huge scale. It keeps the planets in orbit around the Sun. This shows how potential energy works everywhere in our world.

Potential energy is a special kind of energy. It is the energy an object has because of its position.

This energy is stored based on where an object is compared to other things. It can also come from how the tiny particles inside an object are arranged. Scientists often see this energy as being held by a force field. A force field is a space where a force acts on a body. If you work against a force, you store energy in that field.

This stored energy is ready to be used later.

How does this energy work in steps? First, an outside force must do work against a force field. For example, you might lift a heavy ball against gravity. This work is stored as potential energy in the field.

Second, if you remove that outside force, the field acts on the object. The field will then perform work to move the object back. This might cause a ball to fall or a spring to snap back. The energy changes from stored potential energy into movement. This movement is what scientists call kinetic energy.

People have studied these ideas for a long time. Around 1840, scientists began to define work and energy. A Scottish engineer named William Rankine introduced the term "potential energy" in 1853.

He chose this name to pair with the idea of "actual" energy. This idea connects back to the ancient Greek philosopher Aristotle. In 1867, another scientist named William Thomson introduced "kinetic energy." He described it as the opposite of potential energy. Eventually, the term "actual energy" faded away as people used these new names.

There are many specific types of potential energy to know. Gravitational potential energy comes from the pull of gravity.

You can calculate this for objects near Earth. You use the mass, gravity, and the height of the object. Elastic potential energy comes from stretching or squeezing things like springs.

Electric potential energy comes from electric charges. There is even nuclear potential energy from the forces in an atom. Scientists measure all these types of energy using a unit called the joule.

The symbol for a joule is J.

Potential energy is all around us in the world. You can see it when an archer pulls back a bow.

That bow holds elastic potential energy before the arrow flies. You see it in huge machines like a trebuchet.

A trebuchet uses a heavy weight to throw things very far. Even in space, this energy is at work. Gravity holds the planets in their orbits around the Sun.

Understanding potential energy helps us see how the universe stays in motion.

Potential energy is the energy an object or system possesses due to its position relative to other objects. It can also arise from the specific configuration of its particles. This energy is equal to the work done against restoring forces. These forces might include gravity or the tension in a spring. In the International System of Units (SI), energy is measured in joules (J). Potential energy is closely linked to conservative forces. These are forces where the total work done depends only on the initial and final positions of the body. Because the work is path-independent, the energy is stored within a force field.

The mechanism of potential energy involves a clear sequence of cause and effect. First, an external force must perform work against a force field. This action moves an object to a new position or changes its shape. This work is stored in the force field as potential energy. Second, if the external force is removed, the force field acts on the body. The field performs work to move the body back toward its initial position. This process reduces the stored potential energy. As the object moves, the potential energy is transformed into other forms, such as kinetic energy.

Scientists categorize potential energy into several distinct types based on the forces involved. Gravitational potential energy is associated with the force of gravity. Elastic potential energy occurs when an object, like a spring, is deformed by tension or compression. Electric potential energy relates to the work of the Coulomb force between electric charges. There is also nuclear potential energy, which comes from the nuclear force acting on baryon charge. Chemical potential energy is stored in substances like fossil fuels. This energy results from the Coulomb force during the rearrangement of electrons and nuclei in atoms.

The history of this concept involves significant developments in the 19th century. Around 1840, scientists began searching for ways to define energy and work. In 1853, a Scottish engineer and physicist named William Rankine coined the term "potential energy." He developed this term as part of a pair involving "actual" versus "potential" energy. This terminology drew links back to the concepts of potentiality discussed by Aristotle. In 1867, Rankine described potential energy as the "energy of configuration." During that same year, William Thomson introduced the term "kinetic energy." He presented it as the opposite of potential energy. Eventually, the term "actual energy" faded from common scientific use.

Mathematical models allow us to calculate these energy levels with precision. For objects near Earth, gravitational potential energy depends on mass, gravity, and height. The formula uses the mass in kilograms and the local gravitational field, which is 9.8 metres per second squared on Earth. The height is measured in metres above a chosen reference level. For a linear spring, the elastic potential energy is calculated based on the spring's deformation. The work of a spring is proportional to the distance it is stretched or compressed. These calculations require choosing a reference state. This state is often chosen for convenience, such as a height of zero.

Many notable examples demonstrate these principles in action. A trebuchet is a machine that uses the gravitational potential energy of a counterweight. This energy allows the machine to throw projectiles over two hundred meters. In archery, a bow stores elastic potential energy when it is drawn. When the string is released, that energy becomes kinetic energy for the arrow. Even the solar system relies on these forces. Gravitational force keeps the planets in orbit around the Sun.

Potential energy is a fundamental concept that connects to many broader scientific fields. It is deeply tied to the study of vector fields and scalar potentials. In a conservative vector field, the force can be expressed as the gradient of a scalar potential. This mathematical relationship helps physicists understand how forces like electromagnetism and gravity behave. Understanding these configurations allows us to study everything from the movement of subatomic particles to the orbits of massive celestial bodies.