# What Is The Energy Stored Because Of Gravity Or Position Called?

## What is Potential Energy?

Potential energy is the energy stored in an object because of its position or condition. It refers to the capacity for doing work that an object has as a result of its position or state.

For example, a ball held above the ground has gravitational potential energy because of its position. When it falls, this potential energy gets converted into kinetic energy – energy of motion. Other examples are a compressed spring that contains elastic potential energy, or water held behind a dam that contains gravitational potential energy.

Potential energy results from forces that act on an object, such as gravity, magnetism, or molecular bonds. The key is that the object has stored energy that can later be turned into motion. Potential energy is converted into kinetic energy when the object moves under the influence of the force.

In summary, potential energy exists as stored energy in any object or system by virtue of its position or arrangement of parts. It is the energy possessed by a body by virtue of its position relative to others. When the body is moved, the potential energy is transformed into kinetic energy.

## Types of Potential Energy

There are several main types of potential energy:

### Gravitational Potential Energy

Gravitational potential energy is energy stored in an object due to its height above the ground. For example, a book sitting on a shelf has gravitational potential energy that can be converted to kinetic energy if it falls off the shelf. The higher the shelf, the greater the gravitational potential energy of the book. This energy is directly proportional to both the object’s mass and height above the ground.

### Elastic Potential Energy

Elastic potential energy refers to energy stored in elastic materials that are deformed or stretched from their natural state. For example, a stretched rubber band has elastic potential energy that can be converted into kinetic energy if released. The more the band is stretched, the greater its elastic potential energy.

### Chemical Potential Energy

Chemical potential energy is energy stored in the bonds between atoms and molecules. This energy can be released in chemical reactions when the bonds break and reform. For example, the energy stored in gasoline, batteries, and food are examples of chemical potential energy.

### Nuclear Potential Energy

Nuclear potential energy is the energy stored in the nucleus of an atom, released in nuclear fission or fusion. Fission releases energy when heavy nuclei like uranium split into smaller nuclei. Fusion releases energy when light nuclei like hydrogen fuse together into heavier nuclei. Nuclear potential energy is millions of times greater than chemical potential energy.

## Gravitational Potential Energy

Gravitational potential energy is the energy stored by an object due to its position within a gravitational field. The most common example is an object’s height above the ground. The higher up the object is, the more gravitational potential energy it possesses.

Gravitational potential energy is determined by the mass of the object, the acceleration due to gravity, and the height of the object above a reference point, like the ground. The formula for gravitational potential energy is:

GPE = mgh

Where:

• GPE = Gravitational potential energy (Joules)
• m = Mass of the object (kilograms)
• g = Acceleration due to gravity (9.8 m/s2 on Earth)
• h = Height of object above the reference point (meters)

This formula shows that an object gains gravitational potential energy when it is raised up. The higher it goes, the more potential energy it accumulates. This stored energy can later be converted into kinetic energy if the object falls.

## Elastic Potential Energy

Elastic potential energy is the energy stored in elastic materials by stretching or compressing them. Some common examples of elastic potential energy can be found in springs and rubber bands. When these materials are stretched or compressed, the elastic forces within the material push back, storing mechanical energy that can be released when the material returns to its original shape.

The amount of elastic potential energy stored in a material depends on how far it is stretched or compressed. This is described mathematically by the formula:

EPE = 1/2 k x^2

Where EPE is the elastic potential energy, k is the spring constant of the material, and x is the displacement from the equilibrium position. The spring constant measures the stiffness of the material. The more stiff the material, the more energy required to stretch or compress it. The displacement squared term accounts for the fact that stretching a spring twice as far stores four times as much energy.

When the force stretching or compressing the material is released, the material will return to its original shape and release the stored elastic potential energy. This energy can often be harnessed to do work, such as in catapults, bows, and spring-driven motors.

## Chemical Potential Energy

Chemical potential energy is the energy stored in the bonds between atoms and molecules. This energy can be released or absorbed during a chemical reaction. When a chemical reaction occurs, the molecules’ bonds are rearranged, weakened, strengthened, formed, or broken, resulting in the release or absorption of energy. The amount of energy released or absorbed depends on the types of bonds and how they transform during the reaction.

For example, the hydrocarbon molecules in gasoline contain high amounts of chemical potential energy in their carbon-carbon and carbon-hydrogen bonds. When gasoline undergoes combustion in a car engine, these bonds are broken and reformed into water and carbon dioxide, releasing energy that powers the engine. Foods also store chemical potential energy through the bonds in their nutrients. This energy is released in the body during cellular respiration as the nutrients are metabolized and the bonds are altered. The amount of chemical potential energy stored in a substance can be calculated based on the types of bonds it contains and their bond energies. This allows prediction of how much energy could be released or absorbed during a chemical reaction.

## Nuclear Potential Energy

Nuclear potential energy refers to the energy stored in the nucleus of an atom. It is the energy that holds the nucleus together. The nuclear forces that hold the protons and neutrons together have very large binding energies for nuclei. Nuclear potential energy can be released when a heavy nucleus splits into smaller nuclei in a process called nuclear fission. It can also be released when light nuclei fuse together to form a heavier nucleus in a process called nuclear fusion.

Nuclear potential energy is the basis for nuclear power plants, where controlled nuclear fission reactions produce heat that is used to generate electricity. The incredible amount of energy released from the strong nuclear forces holding atomic nuclei together is what makes nuclear fission and fusion viable energy sources.

Nuclear potential energy is also responsible for the destructive power of nuclear weapons like atomic bombs. In an atomic bomb, a uncontrolled chain reaction of nuclear fission rapidly releases the nuclear potential energy locked within uranium or plutonium atoms, creating a devastating explosion.

## Converting Potential to Kinetic Energy

Potential energy converts to kinetic energy when an object moves. For example, a ball raised in the air gains kinetic energy when it is dropped. The ball has potential energy when held at a height due to the pull of gravity acting on its mass. As the ball falls, this potential energy gets converted to kinetic energy, which is the energy of motion.

The principle of conservation of energy states that the total amount of energy in an isolated system remains constant. This means that the sum of all forms of potential energy and kinetic energy is conserved. So when potential energy decreases, there is always an equal increase in kinetic energy. This allows potential energy to be converted into kinetic energy when an object moves.

Some common examples are:

• A pendulum bob gaining speed at the bottom of its swing as it converts gravitational potential energy to kinetic energy
• A drawn bow converting elastic potential energy to kinetic energy as the arrow is released
• Falling water in a hydroelectric dam converting gravitational potential energy to electricity

Understanding the transfer between potential and kinetic energy has many useful applications in science and engineering.

## Potential Energy Equations

There are mathematical formulas that can be used to calculate the potential energy in a system. The specific equation depends on the type of potential energy.

### Gravitational Potential Energy

Gravitational potential energy depends on the mass of an object, the acceleration due to gravity, and the height of the object. It is calculated using the following equation:

PEgrav = mgh

Where:

• PEgrav is the gravitational potential energy in joules (J)
• m is the mass in kilograms (kg)
• g is the acceleration due to gravity (9.8 m/s2 on Earth)
• h is the height of the object in meters (m)

For example, if a 2 kg book is lifted 2 m above the ground on Earth, its gravitational potential energy would be:

PEgrav = (2 kg)(9.8 m/s2)(2 m) = 39.2 J

### Elastic Potential Energy

Elastic potential energy depends on a spring constant and the displacement of the spring. It can be calculated with:

PEelastic = 1⁄2kx2

Where:

• PEelastic is the elastic potential energy in joules (J)
• k is the spring constant in newtons per meter (N/m)
• x is the displacement from the spring’s natural length in meters (m)

As an example, if a spring with a constant of 100 N/m is stretched 0.5 m, its elastic potential energy would be:

PEelastic = 1⁄2(100 N/m)(0.5 m)2 = 12.5 J

This demonstrates how the gravitational and elastic potential energy equations differ in the variables they utilize to calculate the energy.

## Applications of Potential Energy

Potential energy is used in many everyday applications and devices. Here are some common examples:

Roller coasters utilize gravitational potential energy as the chain lift brings the cars to the top of the first hill. The cars then zoom down converting that PE to kinetic energy.

Hydroelectric dams use the gravitational potential energy of water held behind the dam that is then allowed to fall and spin turbines, generating electricity.

Bow and arrows and catapults use elastic potential energy that is stored in the bent limbs as the drawstring is pulled back or the arm is cocked. Releasing fires the arrow or projectile by converting the stored elastic PE into kinetic energy.

Batteries store chemical potential energy from reactions between chemicals and metals. This electrical potential energy can then be tapped and converted to power devices.

Nuclear power plants convert nuclear potential energy from radioactive elements like uranium into heat and electricity through fission and decay processes.

Potential energy powers many essential machines and devices in the modern world. Understanding how to utilize PE through dams, batteries, springs, gravity, nuclear reactions, and more has enabled tremendous advances in technology and engineering.

## History and Discovery

The concept of potential energy was first proposed in the mid-19th century by William Rankine, a Scottish physicist and engineer. Rankine suggested that in addition to kinetic energy, there was another form of energy present in systems due to their configuration. For example, a weight held at a height has energy that could be released as it falls.

The term “potential energy” was coined in 1853 by Rankine’s colleague William Thomson, also known as Lord Kelvin. Thomson was the first to use the term to refer to energy stored in a system because of the relative positions of objects within it. He recognized that a stretched spring, raised weight, charged battery, and separated electric charges all stored energy that could be released to do work.

Key experiments that contributed to the development of potential energy as a concept include Galileo’s experiments on falling bodies in the late 16th century. Galileo showed that gravity accelerates all objects at the same rate regardless of mass. This discovery revealed the connection between an object’s height and the kinetic energy it gains while falling.

In the 17th century, Hooke’s law formally established the relationship between the extension of a spring and the restoring force it exerts. This was a key step in demonstrating elastic potential energy stored in springs.

The full theory of potential energy as we know it today emerged gradually over centuries of scientific inquiry into mechanics, gravity, electromagnetism and thermodynamics. Its development was closely associated with the advent of newtonian physics and the law of conservation of energy in the 19th century.