We talk about energy a lot in our everyday lives from the importance of renewable energy to not wasting energy on certain people or subjects. But how often do we stop to consider what energy is, where it comes from, and where it goes?
Let’s look at potential energy and how it helps us define and understand the world around us. We’ll touch on many concepts from kinetic energy to the Earth’s gravitational field as we discover more about potential energy.
What Is Potential Energy?
In layman’s terms, potential energy is the capacity for something to do work, which is called stored energy. In day-to-day life, think of energy as the effort or amount of work needed to do something.
Potential energy exists because of where things are and their positions relative to each other. For instance, a book on the floor doesn’t have much potential energy, but balance that book atop a skyscraper, and its potential energy increases dramatically. This potential energy can change or alter other objects around it — that book could fall from the skyscraper and cause some real damage to a corn dog cart in the street. There are several types of potential energy, which we’ll discuss below.
What Is the Definition of Potential Energy?
Aristotle (384 BC-322 BC) first wrote about enérgeia, but the concept of energy didn’t start to gain scientific traction until the 17th century. Julius Robert von Mayer, James Prescott Joule, and Hermann Ludwig Ferdinand von Helmholtz (1842-1847) went further. They discovered what we call today the law of conservation of energy, and they called it a “living force” or “fall-force.”
“The law of the conservation of energy still stands; energy cannot be created or destroyed; it can only be transformed from one form to another.” — Leipzig University Germany.
There are two states for all energy: we call these potential energy and kinetic energy.[2,4]
Potential energy is the stored energy of an object relative to its position — it’s energy ready to go. For example, the weight on a raised pendulum has potential energy. Because of the effect of the Earth’s gravity, the potential energy of a hot air balloon is different depending on how high off the surface of the Earth it is.
Kinetic energy is essentially an energy of motion, and is defined as the energy an object or person has due to its motion.
Beyond the state of energy, there are six basic types of energy:
All six of these energy forms can be changed into other forms of energy. The energy is never destroyed, merely transformed.
Physicists often talk about two principal forms of potential energy: gravitational potential energy (the force of gravity) and elastic potential energy (think of a coiled spring). One other form is electric potential energy, which is similar to gravitational potential energy, except it is the electric potential energy of an electric charge in an electric field.
What Does Potential Energy Mean?
The concept of potential energy can be frustrating to grasp — this energy is stored or contained within objects, depending on their position.
Think of it as energy with the potential to do work. If that position, arrangement, or state changes, then stored energy is released.
The coil mentioned previously, or elastic bands and elastic training ropes, are good examples of potential energy. Take an elastic band and use kinetic energy to stretch it. The stretched band now has potential energy. When you release the band (Don’t fire it at anyone!), the rubber band’s elastic force makes it want to return to its natural state, using its potential energy to do so. An archer’s bow works in the same way when firing an arrow.
If a rock falls from a cliff edge, it’s potential energy while perched turns into kinetic energy as it free falls down the hillside.
The food we eat contains potential energy, too. As we eat and digest it, our body turns it into energy so we can move.
Where Is Potential Energy Stored?
Whether stationary or moving, objects have a form of potential energy simply because of where they are located with respect to other objects in the universe.
The easiest way to imagine this is to think about gravitational potential energy. A stationary football on a flat floor has nowhere to go. Pick it up or put it on a hill next to our rock, and now it has the potential to fall or roll. This movement is caused by gravitational force, and the football’s potential energy has changed because of where we have placed it.
An archer’s bow has no energy when in its usual position. Draw it back, and it has stored potential energy. The greater the mass of the object, the greater the gravitational potential energy of an object.
Your potential energy depends on where you are relative to the gravitational force of the Earth. Sleeping in bed in a bungalow means your body has little potential force — you are near the Earth and won’t fall far from the bed. If you are 500 feet from the surface of the Earth, there is a lot more potential energy. If you are suddenly nowhere near Earth, perhaps somewhere near the moon, the Earth’s gravitational force field is weaker, lowering the potential energy of your body.
Snow on flat ground has little potential energy, but piles of snow on top of a mountain has a lot in the event of an avalanche. A book balanced on the edge of a table has potential energy, and so do parked cars.
Lots of electricity comes from nuclear reactors driven by the release of potential energy from atoms. This is what electricity suppliers are harnessing when they use nuclear energy.
Where Does Potential Energy Come From?
To answer this question, we need to return to the conservation of energy law discovered in the 1840s. In short, all the energy we use and experience, from a fire to a wave to a microwave oven, has always been with us, and it always will be. Energy changes its form and has done so since the beginning of the universe.
The Big Bang started a chain of nuclear reactions that formed the universe. The total energy released from this reaction created our sun. The sun we depend on emits heat and light through its nuclear reactions. On Earth, plants convert this light energy via photosynthesis and grow. A chicken consumes plants like corn and grows, using the energy it converts from the corn. In turn, a human eats corn, or a chicken, and our bodies convert it into metabolic energy.
A person uses said energy to cycle up a hill, using metabolic energy to make mechanical energy. This pedaling causes the wheels to turn, and that mechanical energy is now kinetic (movement). The person stops the bike at the top of the hill and both the bicycle and person now have potential energy. If the person releases the brakes and freewheels downhill, the bike moves, and the kinetic energy is released.
This cycle continues, with energy always being returned to the universe as energy or heat.
How To Find Potential Energy?
We can define the amount of work and energy stored as potential energy, and it’s often easier to think of potential energy as stored energy. It requires “work” to store energy. Physics defines work being done as when a force moves an object over a distance.
This “work” is related to energy, and we measure it in joules. To convert work into potential energy, one must act against a force. There are several types of forces, including gravitation or an electric field. The force’s characteristics determine how much energy is stored by working against it.
Remember the person in bed who then moved to the moon? The Earth’s gravitational field, according to Newton’s Laws, explains what is happening to that person’s potential energy. The person is a mass (mass = m) lifted above the ground experiences a force that would make it accelerate towards the ground, called the magnitude of force (F). Newton’s 2nd law is F = mg, with g being acceleration due to gravity, a constant everywhere on Earth.
The person is lifted to a height, represented as h. However you raise a person, it will take some work to get them there, especially if we think about putting them near the moon. The amount of work you do to achieve this is force × distance, or mgh. That work is now stored as potential energy. The potential energy equation for earth’s gravitational field is:
Gravitational Potential Energy = mgh
If you want to find something’s potential energy, this handy energy calculator is a good reference point.
What Is an Example of Potential Energy?
Nuclear energy is an important example of potential energy. The Big Bang’s nuclear reactions created the universe and our sun, which brought life to Earth.
Humans harness nuclear power’s potential to drive our economies, and nuclear often forms part of the energy mix for our homes.
Protons and neutrons are present inside the nucleus of an atom, which is surrounded by electrons, and their potential energy binds them together in the nucleus. When two or more atomic nuclei are combined, or split into two smaller nuclei, a large amount of nuclear energy is released as heat and light.
What Are Forms of Potential Energy?
There are two main types of potential energy. The first is gravitational potential energy. Gravitational potential energy increases as the height and the mass of the object increase. A 210-pound person standing atop a 100-foot pylon has more gravitational potential energy than a 140-pound person standing atop a 50-foot pylon.
The second form of potential energy is elastic potential energy. This is the energy stored in objects that can be stretched or compressed. The elastic potential energy of an object depends on how much it can be stretched or compressed. The more it can be stretched or compressed, the more elastic potential energy it has.
What Is Potential Energy Measured In?
Potential energy is measured in joules, using the symbol J in the International System of Units (SI). To understand why we use joules, we must travel back to the 17th century to when Isaac Newton was hit by falling apples.
One joule is equivalent to a person raising an apple to a height of one meter. It’s the amount of work that the body does to lift it one meter — work that changes the energy in the body. As energy and units of work are interchangeable, we use joules to calculate potential energy.
An apple is often used not only because of Newton’s relationship with apples but because most apples weigh around one Newton, which is 0.2248 pounds (just shy of 102 grams). One Newton is the force that would give a mass of one kilogram (2.2 pounds) an acceleration of one meter (3.28 feet) per second.
So, it takes one Newton of upward force to lift the apple, and it takes you one joule of work to do that. While you do this, the apple’s potential energy changes, and at its one-meter peak, the apple has gained one joule of potential energy.
If you release the apple, the force of gravity will perform one joule of work on it as it drops one meter in height.
Which Is an Example of Potential Energy?
You can see examples of potential energy all around you in day-to-day life.
The book on the edge of the table? It has gravitational potential energy. If you knock it off the table, its potential — or stored — energy is released as kinetic energy as it falls to the ground. When it hits the ground and makes a noise, some of that collision’s energy is converted into mechanical energy as sound waves.
Renewable energies use this concept a lot. Water or wind turbines take the kinetic energy from wind or fast-flowing water to drive turbines, creating mechanical energy. A generator turns this into electrical energy, and energy transforms from one energy type to another. We can choose to use this renewable energy through our energy supplier.
Potential Energy’s Role on Earth
Potential energy forms an essential part of our understanding of and place in the universe. In fact, the position of objects within the universe is what defines potential energy alongside the work required to move said objects. Everything we do affects the potential energy of things.
Knowing we never lose energy and there is simply an energy transfer into different forms of energy is vital to our planet’s future. If everything is energy, it follows that burning fossil fuels creates emissions and transforms the potential energy of some of the earth’s resources into pollutants.
Switching to renewables offers us the chance to create useful electrical energy from clean sources and harness the potential energy of a system of power that’s been with us since the beginning of the universe.
Brought to you by amigoenergy
All images licensed from Adobe Stock.
- Science Daily. Potential Energy. https://www.sciencedaily.com/terms/potential_energy.htm. Accessed November 2, 2020.
- Chemistry LibreTexts. Introduction to Kinetic and Potential Energy. https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_Chem_309_-_General_Organic_and_Biochemistry_(Bennett)/Text/01._Measuring_Matter_and_Energy/1.03%3A_Introduction_to_Kinetic_and_Potential_Energy. Updated August 13, 2019. Accessed November 2, 2020.
- Leipzig University. Energy Fundamentals. https://home.uni-leipzig.de/energy/energy-fundamentals/01.htm. Accessed November 2, 2020.
- The Clay Centre. More On Energy. https://www.theclaycenter.org/wp-content/uploads/2016/10/Energy-Curriculum-Forms.pdf. Updated October 2016. Accessed November 2, 2020.
Xactly. Potential Energy. http://xaktly.com/PotentialEnergy.html. Accessed November 2, 2020.
- Prezi. Hot Air Balloon.https://prezi.com/mistfvii5u2e/hot-air-balloon/ – :~:text=than the air.-,Hot air rises,Potential energy is stored energy.&text=Kinetic energy is the energy,balloon gets exposed to heat. Updated May 5, 2015. Accessed November 20, 2020.
- Solar Schools. Potential Energy. https://www.solarschools.net/knowledge-bank/energy/forms/potential. Accessed November 2, 2020.
- Northwestern Education. Where does energy come from? Where does energy go? https://www.qrg.northwestern.edu/projects/vss/docs/thermal/3-where-does-energy-come-from-and-go.html. Accessed November 2, 2020.
- Sciencing. How to Calculate Potential Energy. https://sciencing.com/calculate-potential-energy-4514673.html. Updated October 30, 2016. Accessed November 2, 2020.
- Universe Today. What Is A Joule? https://www.universetoday.com/61490/what-is-a-joule/. Updated April 6, 2010. Accessed November 2, 2020.
- Physics and Radio Electronics. Nuclear Energy. https://www.physics-and-radio-electronics.com/physics/energy/potential-energy/nuclear-energy.html. Accessed November 2, 2020.
- AWEA. Basics of Wind Energy https://www.awea.org/wind-101/basics-of-wind-energy#:~:text=When%20the%20wind%20blows%20past,a%20generator%20that%20produces%20electricity. Accessed November 20, 2020.