Potential and Kinetic Energy Explained

by | Educational, Energy, Science and Technology

All the energy in the universe is either potential energy or kinetic energy.  

The interaction and definition of these two energies are vital to our understanding of the world around us. Let’s take a look at what potential and kinetic energy mean, the relationship between them, and some examples of each. 

What Is Potential and Kinetic Energy, and What Are Their Differences? 

Potential energy is stored energy. An object has a measurable amount of potential energy depending on where it’s located and how it relates to other objects around it — the energy of position.[1] 

An apple on the floor has very little potential energy. Lift it to the top of a skyscraper, and suddenly it has a lot of potential energy. It can fall to the ground under the force of gravity. It can also interact with other objects on its descent, such as striking a flying bird or landing on a car roof and damaging it. 

When the apple is descending, its potential energy has become kinetic energy, which is the energy of motion. Kinetic energy is the energy a person or an object has due to its motion in this example, the falling apple. A parked bike on top of a hill has potential energy, which becomes kinetic energy once you start riding it downhill. 

Both of these energies are measured in joules. Energy is never destroyed or lost when changing from potential energy to kinetic energy — it is merely transformed from one energy type to another. This is known as the law of conservation of energy.[2] 

The potential energy of an object cannot be transferred to another entity – you cannot suck the potential energy out of the apple atop a skyscraper. Kinetic energy is transferable, as witnessed with the falling apple’s kinetic energy damaging a car or hitting a bird.  

What Is the Relationship Between Potential and Kinetic Energy? 

Relationship Potential and Kinetic Energy explained | Waterfall energy image

The relationship between potential energy and kinetic energy is that potential energy can transform into kinetic energy. 

Potential energy is position relative. In other words, it changes depending on an object’s height or distance and the mass of the object. Kinetic energy changes depending on an object’s speed and its mass. 

If we think about a waterfall, some still water at the top of the waterfall has potential energy. It isn’t moving and hasn’t gone over the edge. The water flowing from the waterfall has kinetic energy as it flows.[3] 

A pendulum is an excellent example of this relationship. As the pendulum swings ever higher upwards, its potential energy increases until it reaches its optimum at the highest point of the swing. At the top of the arc, the potential energy turns into kinetic energy as it swings back down.[4] 

What Are Examples of Potential Energy? 

There are two primary types of potential energy: gravitational potential energy and elastic potential energy. 

The gravitational force of the Earth causes gravitational potential energy. When a person jumps from a high dive board, they land with much force (and a splash) into the swimming pool below.  

The Earth’s gravity uses the diver’s gravitational force (their weight) to produce the kinetic energy (movement) that brings the diver into the pool. At the top of the diving board, we can talk about the diver’s gravitational potential energy. 

This is the same for apples on trees, bikes on top of a hill, a roller coaster waiting to descend, and a skydiver in a plane — all examples of the potential to do an amount of work.[5] 

Elastic potential energy occurs when you stretch or compress something. A rubber band left on a sideboard has little potential energy. If you pick it up and stretch it, you have increased its potential to do some work.  

If you release the rubber band, it may fly across the room or scare the cat. You manipulated the rubber band to increase its potential energy, which was then released as kinetic energy as it traveled (motion) across the room. An archer pulling back a bow and coiling a spring are further examples of potential energy.[6] 

Specific Variations:

Potential Energy Electron image | Looking at Variations of Energy

Having defined the main types of energy, we can look at more specific examples and deduce if they have kinetic or potential energy.  

What Is the Potential Energy of an Electron? 

Atoms are made up of protons, neutrons, and electrons. Atoms can transfer potential and kinetic energy.  

An atom has a nucleus, and electrons orbit that nucleus, which is kinetic energy. Suppose we apply energy or pressure to the atom. In that case, it increases the electrons’ kinetic energy and they start to move more quickly. Eventually, the electrons jump out into a wider orbit of the nucleus. This electron has now stored this energy, this potential energy.[7] 

At some point, the electron will release this potential energy, converting into kinetic energy as it returns to its previous, smaller orbit. The potential energy is released as visible light or heat, both types of kinetic energy.[7]  

An electron’s total energy is the sum of its kinetic and potential energy.[8] 

For more details, consider this formula[9] for calculating the potential energy of an electron.  

Is a Battery Kinetic or Potential Energy? 

Batteries are a form of electrical potential energy. They produce electrical energy via a chemical reaction that occurs when positive and negative charges are separated.[10] 

When you turn on a battery-operated device, its potential energy stores of chemical and electrical energy are released and become other kinetic energy forms. When turned on, a handheld torch releases light energy and thermal energy, a form of kinetic energy. A battery-powered singing and cycling toy monkey atop a bike will produce mechanical energy as it cycles around, and sound energy while singing its song.[11] 

A battery stores potential energy that transforms into kinetic energy. The mobile phone battery you may be reading this on stores potential energy and converts it to kinetic energy (light, thermal), allowing your phone to function. 

Is Electrical Energy Potential or Kinetic? 

Electrical energy can be potential or kinetic energy. It results from the flow of an electric charge. As discussed, energy can be seen as the work required to move an object or subject it to force. For electrical energy, this force, energy, or “work” is the electrical attraction or repulsion between charged particles.  

The current of electricity most commonly talked about occurs when these charged particles travel through a wire.  

Like a battery, electrical energy is often potential energy until some force or is applied to make the charged particles do some work and become kinetic energy. When you switch on your light at home, the potential energy travels down the wire and is converted into light and thermal energy.[12] 

It’s enjoyable to think about the conservation of energy and how, for example, renewable energy like wind power takes energy from wind and converts it into usable electrical energy for our homes.  

Is Sound Energy Potential or Kinetic? 

Sound energy comes in both potential and kinetic energy forms. Sound energy is released by vibrating objects in the form of a wave.[13] 

An excellent example of sound energy is a tuning fork. When it lies on the table, it has the potential to create sound energy, which is potential energy. Once you strike it, it vibrates and emits sound waves. These waves oscillate and travel, which is kinetic energy.  

Sound travels around four times faster in water than in air. At sea level, the speed of sound is approximately 767 miles per hour (1,230 kilometers per hour).[14] 

Is Thermal Energy Potential or Kinetic? 

Thermal Energy Example | Types of Potential vs Kinetic Energy

Thermal energy is also called heat energy. Remember the excitable electrons and atoms from earlier? Thermal energy is produced when these atoms and molecules are moving faster. They are moving more quickly because of the rise in temperature.[15]  

We need to stay at a molecular level to understand that thermal energy is also potential and kinetic energy. All matter, made up of atoms and molecules, is always moving. They have potential energy. Whenever a substance heats up, the molecules and atoms within move more quickly, banging into each other and releasing thermal energy as heat.[15] 

Think about a kettle boiling. The water molecules move faster as the water heats, and this movement is kinetic energy. When the water boils, its steam moves. The thermal energy released from the atoms and molecules has produced kinetic energy. 

More examples include the heat from an electrical heater or when you put food in the oven to bake; when you put cold milk in a hot drink like tea, some of the tea’s thermal heat is passed to the milk.[16] 

Is Radiant Energy Potential or Kinetic? 

Radiant energy is a form of kinetic energy. It is the energy of electromagnetic waves that can travel through space.  

The sun is a vast source of radiant energy on Earth. For example, plants absorb electromagnetic waves and, via photosynthesis, produce their food. When the sun’s radiant energy touches our skin, the waves make our skin’s molecules move faster, and we feel warmer.[17] 

We can see radiant energy waves as light energy — the only form of energy the human eye can see. Radiant energy’s magnetic waves can also be invisible, such as X-rays and radio waves.[18] 

Variations of Potential Energy 

It’s time to look at more specific examples and names for different types of energy. 

There are six primary groups[19], some of which we have examined already: 

  • Nuclear energy; energy released during nuclear fusion.[7] 
  • Mechanical energy; sum of potential and kinetic energy.[20] 
  • Chemical energy; energy stored in compounds and elements. [21] 
  • Electrical energy; potential or kinetic energy resulting from the flow of an electric charge.[12] 
  • Radiant energy; electromagnetic waves that travel through space.[17] 
  • Thermal energy; heat or thermal energy produced by rises in temperature.[15,19] 

We recognize nuclear and electrical energy when choosing electricity suppliers for our homes, for example. 

What Is Chemical Potential Energy? 

Chemical potential energy, in its simplest form, is energy stored in compounds and elements. These elements and compounds are made up of atoms and molecules that have atomic bonds. Chemical processes can break these atomic bonds, releasing the potential energy of the atomic bonds and providing energy.[21] 

Every day we use the chemical potential energy in food to give energy to our bodies. We eat food (a compound or element), and our digestive system (chemical process) turns the potential energy of the food into chemical energy. We can then do work with this energy.[22] 

Combustion energy does something similar to gasoline. The chemical process splits the complex gasoline molecule into smaller molecules (carbon dioxide and water). The energy released produces heat, which powers the now moving car, the car’s movement being kinetic energy.[22] 

Define Gravitational Potential Energy 

Two rocks — one big, one small — balancing on a 100-foot cliff edge are good ways to think about gravitational potential energy. This potential energy is defined as the energy an object holds relative to its vertical position. It increases as either the height or the mass of the object increases, or both. This is due to the Earth’s gravitational field.[23] 

Back to our rocks. The bigger, heavier rock has more potential energy than the smaller rock since the mass of the object is greater than the smaller rock. Let’s push the large rock from the cliff edge and turn that potential energy into kinetic energy. It comes to rest in the valley below and has very little potential energy. Our smaller rock now has more potential energy than the stationary larger rock, thanks to its vertical position. 

Similarly, two identical rocks can have different levels of potential energy. If one is 100 feet up and the other is at 500 feet, the higher rock has more potential energy because it has further to fall.[24] 

The Science of Energy:

Potential Energy in Science, Physics, and Chemistry

The principles of energy, based on Newton’s Laws, have helped us understand the world around us as well as the universe.  

What Is Potential Energy in Physics? 

Potential energy is the stored or latent energy in an object at rest. It’s fundamental to many physics-related concepts because its laws hold true on any level, from the planetary to the atomic level. 

The potential energy of an object is measurable. The amount it has depends on where the object is located — its energy of position — and the mass of the object. 

Many objects transform their potential energy into kinetic energy.  

What Is Potential Energy in Chemistry? 

Chemical potential energy is released when atomic bonds stored in compounds and elements are broken via chemical processes. This chemical energy is then used in other ways, in what is called work. Energy and work are essentially the same things — work is energy in motion. 

 What Is Kinetic Energy and Potential Energy Formula? 

Potential energy, or work, is measured in joules, named after James Prescott Joule, an English mathematician whose work created the formula about energy and its transference.[25]  

Joule is written with the symbol J in the International System of Units (SI), and the formula is written thus:[25] 

m is the mass of our object[26] 
h is the height of our object[26] 
g is the acceleration due to gravity, a constant all over the Earth[26] 

If we lift our object from the ground to give it potential energy, the force that would make it accelerate towards the ground is called the magnitude of force (F). Newton’s second law is F = mg.[26] 

Which gives: Gravitational Potential Energy = mgh[26] 

If we lift a 200 pounds person 100 feet in the air, their potential energy is 27,116.36 joules. Try this handy calculator to calculate potential energy. 

The kinetic energy of an object is also measured in joules. Anything that is moving has kinetic energy, but various factors affect how much kinetic energy an object has. 

The first factor is speed. If two identical objects are moving at different speeds, the faster object has more kinetic energy. A moving car traveling at 2 miles per hour has a lot less kinetic energy — the energy of movement — than the same vehicle traveling 100 miles per hour. 

The second factor is mass. If two objects are moving at the same speed, but one of the objects has more mass, the heavier object has more kinetic energy. Using the car analogy again, a bicycle going at 20 miles per hour has less kinetic energy than a dumpster going at the same speed. 

Kinetic energy is noted as E, Ek, or KE. It is half the mass of an object multiplied by its velocity squared. So it is proportional to mass (m) and proportional to the square of its velocity. The formula is written:[27] 

Kinetic energy: KE = ½ mv2 

If our 200-pound person is running at 8 miles per hour, their kinetic energy is J 580.15 joules.  

For further details, you can read more about energy formulas.[28] 

It’s All Energy, Potentially 

Potential and kinetic energy are part of the enormous energy of our universe. They’re different forms of energy, but they are closely linked and are measured using the same units (joules). 

Energy is never lost; it merely transforms into other forms of energy. It’s useful to know where energy comes from and how it impacts your day-to-day life when choosing an energy supplier. Ultimately, it helps us comprehend the environment and our place in the universe.  

Brought to you by amigoenergy.com

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