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# Forms of Energy

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What does one mean when they say they feel energetic today? Is it the same energy that powers cars, buses, planes, and other modes of transportation? If not, can we convert one type of energy to another? To answer these questions, it is essential to understand the different forms of energy present in our universe. Some energies are abundant such as light energy, whereas others are limited due to resources. This article goes through the definition of energy, different forms of energy, and how it can be transferred from one form to another?

## What is energy?

Energy is what moves the world around us. It is always transferred whenever a physical action (even at atomic levels) takes place, or the state of a system is changed. A system is defined as an object or a group of objects with a defined boundary. Systems can be of 3 types:

• An open system is one in which matter and energy can be exchanged with the surroundings.
• A closed system is one in which only energy can be exchanged with the surroundings.
• An isolated system is one in which neither matter nor energy can be exchanged with the surroundings.

There are 3 types of thermodynamic systems, the first tube is an open system, the second tube with a closed mouth is called a closed system and finally, the system that is completely separated from the system is called an isolated system, Mayyskiyysegreyy CC-BY-SA4.0

## Forms of Kinetic Energy

We must apply an external force to accelerate an object. As a consequence work must be done, which can mean only one thing. Energy needs to be transferred when the object moves at a new constant speed. The energy transferred is known as kinetic energy.

Kinetic energy is a form of energy that an object has due to its motion.

When an external force causes an object to move, work is done i.e. energy is transferred. This is the kinetic energyof the object. It is measured inor. Kinetic energydepends on two factors. The mass of the object and the velocity at which it's moving

Examples of Kinetic energy in everyday life, kinetic energy is perhaps the most often observed form of energy and the most intuitive to humans, StudySmarter Originals

It can also be defined as the work done on an object of massto accelerate it to a speed. The same amount of work will be done to bring this moving body to a stop. however, the work done will be negative because it is against the motion of the object.

or in words

The kinetic energy of a moving body depends on two factors, its velocity, and mass.

or in words

Kinetic energy can be present in different forms, such as translational and rotational kinetic energy. We will look into mechanical and heat energy in detail as they're important. Later we will also discuss the other forms of kinetic energy.

## Mechanical energy

One of the fundamental laws of the universe is that energy can neither be created nor destroyed; it can only be transferred from one form to another. This principle is known as the conservation of energy. What this says is the total energy inside a system is always constant. So then, what are these different forms that we've been talking about so far?

When a fossil fuel undergoes combustion, it converts the chemical energy stored in the fuel into thermal energy. If you consider such an isolated system, the amount of energy is always constant; it just changes from one form to another.

So then what is mechanical energy?

Mechanical energy is the energy possessed by an object due to its motion, such as a speeding car, falling leaf, etc, or by virtue of its position.

It is given by the following equation:

or in words

Potential energy is also known as stored energy. When someone says that they have the potential to do great things, they're talking about something innate or hidden within the subject. The same logic applies when describing potential energy. Potential energy can be broken down based on the system and the forces acting on it. we'll look into potential energy in detail in the later sections. But take a look at the example below to understand how the mechanical energy of an object remains constant?

The mechanical energy of a vehicle on a hill, over the journey of the object the mechanical energy will remain constant, dummies

When the object climbs the hill its potential energy is constantly increasing, but as its speed is decreasing the kinetic energy keeps on reducing. at the top of the hill, the potential energy is maximum and the kinetic energy is Zero. When the object travels downhill, its potential energy starts decreasing and the kinetic energy keeps increasing. As shown in the figure the sum of both energies will always be constant, which again follows the principle of conservation. Throughout the journey, the energy is transferred from one form to another.

## Heat energy

Heat or thermal energy is produced due to the rapid motion of atoms. It can be said that this is due to the kinetic energy of the atoms, molecules, or ions. Heat transfer happens from a point of high temperature to low temperature. There are 3 ways of transferring heat between two bodies. Conduction, convection and radiation.

Conduction is when heat energy is transferred between neighbouring atoms or molecules due to collisions between them.

Convection is the upward movement of molecules and atoms with a higher temperature causing the denser and cooler molecules to sink inevitably causing heat transfer.

Radiation is a process in which heat waves are emitted and may be absorbed, reflected, or transmitted through a colder substance leading to the transfer of heat.

Let's understand this using an example,

This image represents heat transfer taking place by conduction, convection and radiation, simscale.com

When Heating a pot of water, heat transfer takes place using the three methods heat transfer through conduction occurs when the metal handle is heated as heat transfers through the metal pan. Next. Radiation occurs as the infrared waves heat the bottom of the pan. And finally, heat transfer due to convection occurs when the water molecules at the bottom rise and transfer heat.

The change in thermal energy can be given by the following equation:

or in words

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

### Other Forms of Kinetic Energy

We already know that kinetic energy can be stored in different ways and is measured in. These forms of kinetic energy are nothing but the different ways kinetic energy is transferred throughout the universe.

• Sound energy - Speakers convert electric energy into sound waves. The sound waves transfer energy throughout the air molecules as vibrations, and we hear music. The sound waves are produced due to the kinetic energy of the air molecules.
• Radiant energy or Light energy travels as electromagnetic radiation. Light energy is released when photons dissipate energy into the surroundings; this is what we see as visible light. Energy transfer occurs when the light comes in contact with an external surface - for instance, photosynthesis in plants and light falling on solar panels. The sun is the largest source of light energy.

We now have a clear idea of kinetic energy and its many forms. Now, let's look at another type of energy that is mostly stored in objects and when released can be converted into kinetic energy.

## Gravitational Potential Energy

Why does a rock dropped from a great height into a pool produce a much bigger splash than one dropped from just above the water surface? What has changed when the same rock is dropped from a greater height? When an object is elevated in a gravitational field, it gains gravitational potential energy (GPE). The elevated rock is at a higher energy state than the same rock at surface level, as more work is done to raise it to a greater height. It is called potential energy because this is a stored form of energy that when released is converted into kinetic energy as the rock falls.

Gravitational potential energy is the energy gained when an object is raised by a certain height against an external gravitational field.

The gravitational potential energy of an object depends on the height of the object, the strength of the gravitational field it is in, and the mass of the object.

The water is stored at a height as stored potential energy. When the dam opens it releases this energy and the energy is converted into kinetic energy to drive the generators, Lijovklm CC-BY-SA-4.0

Water stored on top of a dam has the potential to drive hydroelectric turbines. This is because gravity is always acting on the body of water trying to bring it down. As the water flows from a height its gravitational potential energy is converted into kinetic energy. This then drives the turbines to produce electricity (electrical energy). All types of potential energy are stores of energy, which in this case is released by the opening of the dam allowing it to be converted into another form.

The gravitational potential energy gained by an object of masswhen it is lifted to a heightin a gravitational field ofis given by the equation:

or in words

whereis the gravitational potential energy in,is the mass of the object in,is the height in, andis the gravitational field strength on Earth. But what about the work done to raise an object to a height? We already know that the increase in potential energy is equal to the work done on an object, due to the principle of conservation of energy:

or in words

Because potential energy is a stored form of energy, it can be stored in different forms. Potential energy can also be stored in the bonds of chemicals or a stretched object. Let's look at these in detail.

## Chemical Potential Energy

Chemical energy is a type of potential energy that is stored in the bonds between the atoms or molecules of different compounds.

This energy is transferred when the bonds are broken during chemical reactions. Common examples of chemical energy are:

• The combustion of coal converts the chemical energy into heat and light.
• Batteries store chemical energy which is converted into electric energy.
• Sunlight falling on leaves converts light energy into chemical energy.

Nuclear potential energy is the energy that is within the nucleus of an atom. It is one of the most powerful sources of energy in the universe. Nuclear energy can be released by

Nuclear fission and fusion, Padsohot CC-BY-SA-4.0

• Fusion - Energy is released when two small nuclei combine such as the isotopes of hydrogen-deuterium and tritium combining to form helium and one free neutron.
• Fission - Energy released by breaking down a parent nucleus into two different nuclei known as the daughters. The nucleus of an atom like Uranium can break down into smaller nuclei of equal masses with the release of energy.
• Radioactive decay - Unstable nuclei dissipate energy in the form of harmful radioactive waves (nuclear energy to radiation energy).

## Elastic potential energy

The energy stored in elastic materials as a result of stretching or compressing is known as elastic potential energy.

It is given by the following equation

or in words

whereis the constant of elasticity of the material and x is the distance to which it is stretched. It can also be defined as the work done to stretch a rubber band of elasticityby extension.

The spring in this figure is stretched by a force that causes it to extend. If we know the distance over which it extends and its spring constant, we can find the elastic potential energy that is stored in it, StudySmarter Originals

In the figure above a spring with spring constantis stretched by a forceover a distance. The spring holds elastic potential energy. Once released this potential energy moves the rubber band to its original position. It can also be defined as the work done to stretch the spring over a certain distance. The energy released will be equal to the work that was required to stretch the spring.

## Examples of Energy Transfer

Whenever the state of a system changes energy is being transferred from one state to another, energy can be transferred by the following types of energy transfers. Let's see how energy is transferred in the world around us

• Mechanical energy transfer
• Electrical energy transfer
• Thermal energy transfer

We also know another way of saying work is done is by saying that energy was transferred from one form to another. Let's work on a few examples that will test your understanding of the concepts we covered in this article.

Calculate the braking force required to stop a vehicle of massmoving at a speed ofin.

We know that work done to stop a moving vehicle is equal to the kinetic energy of the moving vehicle. Using this we can equate both the terms of work done and kinetic energy. From there we can calculate the force that will be required to stop this vehicle.

So the force required to stop this vehicle is. Let's simplify this problem and try to understand how energy is being transferred from one form to another.

The brakes clamp down on the moving wheel, the brake showed is a high friction material that converts the kinetic energy of the wheel into heat, and in this process, the bike slows down, Wikimedia Commons

When we push or pull an object mechanical energy is transferred. In this case, the mechanical energy is being transferred. let us look at the case of a speeding bike. The bike has kinetic energy due to its mass and the velocity at which it is moving. Now let's imagine, that the rider presses the brake lever. Here the friction from the brakes converts the kinetic energy of the moving vehicle into heat. This is an example of how energy transfer converts the kinetic energy of a moving vehicle and stops it. in the above image, you can see how the brake lever pushes the brake shoes onto the wheels which ultimately slows it down.

What about the energy conversions when an object is falling? let's find that out using our next example.

If aapple is dropped from a height ofabove the ground, at what speed will it hit the ground? Ignore any effects of air resistance.

The speed of a falling apple increases as it is accelerated by gravity, and is at a maximum at the point of impact, StudySmarter Originals

The gravitational potential energy of the object is converted into kinetic energy as it falls and increases in velocity. Therefore the potential energy at the top is equal to the kinetic energy at the bottom at the time of impact. using the equation for mechanical energy.

The total mechanical energy of the apple at all times is given by:

When the apple is at a height of, the velocity is zero hence. Then the total energy is:

When the apple is about to hit the ground the potential energy is zero, hence the total energy is now:

Velocity during impact can be found by equating theto. At the moment of impact, the kinetic energy of the object will be equal to the potential energy of the apple when it was dropped.

The apple has a velocity ofwhen it hits the ground. The potential energy of the apple is converted into kinetic energy as it falls.

## Forms of Energy - Key takeaways

• Energy is defined as the capacity to do work.
• Energy can neither be created nor destroyed it can only be transferred from one form to another.
• The energy of a system is always constant
• Energy can be transferred in the form of mechanical, light, electric potential, nuclear, gravitational potential, chemical, and heat.
• Mechanical energy is the sum of kinetic and potential energy, Kinetic energy is due to the motion of an object.
• Potential energy can be of many types depending on the nature of the forces acting on the body.
• Potential energy can be defined as the work done to move an object to a certain height in a gravitational field
• Whenever a system changes its state, energy is transferred from one form to another.
• Transfer in energy can be in the form of heat, radiation, electrical, and mechanical.

Light energy is released when photons carry energy into the surroundings; this is what we see as visible light. Energy transfer occurs when the light comes in contact with an external surface. An example of light energy is photosynthesis in plants, light falling on solar panels. The sun is the largest source of light energy.

Heat or thermal energy is produced due to the rapid motion of atoms. It can be said that this is due to the kinetic energy of the atoms, molecules, or ions. Heat transfer happens from high to low temperatures due to conduction, convection and radiation.

Gravitational energy is generated when an object is lifted to a certain height in the earth's gravitation field. it can also be defined as the work done to lift an object to a certain height h in the field

Chemical energy is a type of potential energy stored in the bonds between the atoms or molecules of different compounds. This energy is transferred when the bonds are broken during chemical reactions.

Examples of mechanical energy are a moving car (kinetic energy), a hydrostatic turbine rotated by the flow of water, and A bullet fired from a gun.

## Final Forms of Energy Quiz

Question

What is the principle of conservation of energy?

Energy can neither be created nor destroyed It can only be transferred from one form of energy to another

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Question

What are the different forms of energy?

• Electrical Potential Energy
• Nuclear Energy
• Mechanical Energy
• Light Energy
• Heat energy
• Gravitational Potential Energy.
• Chemical Potential Energy.

Show question

Question

Which energy is released by chemical reactions?

Chemical Energy

Show question

Question

What are some examples of mechanical energy?

Examples of mechanical energy are a moving car (kinetic energy), a hydrostatic turbine rotated by the flow of water, A bullet fired from a gun.

Show question

Question

What is chemical energy?

Chemical energy is a type of potential energy that is stored in the bonds between the atoms or molecules of different compounds. This energy is transferred when the bonds are broken during chemical reactions.

Show question

Question

How is gravitational potential energy generated?

Gravitational potential energy is generated when an object is lifted to a certain height in the earth's gravitation field. it can also be defined as the work done to lift an object to a certain height h in the field.

Show question

Question

What are the causes of heat energy?

Heat or thermal energy is produced due to the rapid motion of atoms. It can be said that this is due to the kinetic energy of the atoms, molecules, or ions. Heat transfer happens from a point of high temperature to low temperature due to conduction, convection and radiation.

Show question

Question

What is light energy with examples?

Light energy is released when photons dissipate energy into the surroundings, this is what we see as visible light. Energy transfer occurs when the light comes in contact with an external surface.

Examples of light energy is photosynthesis in plants, light falling on solar panels. The sun is the largest source of light energy.

Show question

Question

Which of the following types of energy is produced when an object is raised to a certain height?

Potential energy

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Question

Which energy is stored in moving objects?

Kinetic energy

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Question

Heat energy is transferred from low temperature to high temperature

False

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Question

Can light energy be stored?

False.

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Question

What is the largest source of energy in our solar system?

The sun is the largest source of energy in our solar system.

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Question

Which energy is released when the nucleus of an atom is split apart?

Nuclear energy

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Question

Which of the following is a mode of heat transfer?

All the options

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Question

Kinetic energy (Ek) is the ...

Energy in a falling object

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Question

If the speed is doubled then the kinetic energy is ...

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Question

The kinetic energy is a vector quantity.

False

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Question

The kinetic energy of an object can be negative.

False

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Question

Which of the following has kinetic energy?

A speeding bullet

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Question

How is Kinetic energy measured?

in Joules

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Question

Kinetic energy can also be defined as ...

All the options

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Question

Which energy is transferred when a bullet hits a target?

Kinetic to heat

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Question

What is potential energy?

Potential energy EPE, is a form of energy that depends on the relative position of an object within a system.

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Question

What is an example of potential energy?

Examples of potential energy are

• Raised object
• Stretched rubber band
• Water stored in a dam
• The energy released during nuclear fusion and fission of atoms

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Question

What are the 4 types of potential energy?

The 4 types of potential energy are

• Gravitational Potential Energy
• Elastic Potential Energy
• Electric Potential Energy
• Nuclear Potential Energy

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Question

What is the difference between potential and kinetic energy?

Potential energy is a stored form of energy due to the relative position of an object within a system whereas, kinetic energy is due to the motion of the object

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Question

Which of these objects has the highest gravitational potential energy?

A ball at the top of a hill.

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Question

Potential energy can be due to ...

Gravity

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Question

The SI unit of potential energy is ...

Joules

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Question

When does a ball that is thrown vertically upward have the highest potential energy?

At the top of its journey

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Question

Gravitational potential energy depends on ...

All the options

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Question

Two balls are placed at the same height with the exception of one being on the earth and the other on the moon. Which will have higher gravitational potential energy?

Ball on the earth

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Question

What is elastic potential energy?

The energy stored in elastic materials as a result of stretching or compressing is known as elastic potential energy.

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