The term ‘Potential Energy’ was coined by a Scottish mechanical engineer William Rankine in the 19tn century. It soon became one of the most influential variables in the formulas the describe our known universe.
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What Is Potential Energy?
Potential energy is the energy stored within an object. This stored energy is based on the state, arrangement, or position of the object.
Alternatively, you can imagine it as an energy that has the ‘potential’ to do work. When the state, arrangement, or position of the object changes, the stored energy is released.
While the potential energy can be defined as the latent energy stored in a substance at rest, its other form, called kinetic energy, is expressed by a substance in motion.
Types Of Potential Energy
There are different types of potential energy, each associated with a specific type of force. The four major types are
- Gravitational Potential Energy: is the energy in an object when it is held vertically at some altitude.
- Elastic Potential Energy: is the energy stored in an object when it is stretched or compressed.
- Electric Potential Energy: is the energy in an object due to its charge.
- Chemical Potential Energy: is the energy stored in the chemical bonds of a substance.
Each of them is measured differently. For example, the gravitational potential energy (PE) is proportional to the mass (m) of an object, gravity (g), and height (h) at which the object is held.
PE = m.g.h
The more the mass of an object and the higher it is held, the more will be its potential energy. Like all other forms of energy, potential energy is measured in kilograms-meters squared per second squared (kg m2/ s2) or Joule (J).
To better explain this phenomenon, we have gathered some interesting examples of potential energy that you see in your everyday life.
1. A Pendulum
Type: Gravitational Potential Energy
In a simple pendulum, a bob is attached to the end of a nearly massless string that swings about a pivot. As the pendulum swings back and forth, the energy is transformed between potential energy and kinetic energy.
The bob carries the maximum potential energy at one end. As it swings towards the bottom-most point under the influence of gravity, its potential energy starts converting into kinetic energy.
The potential energy of the bob reaches zero (and kinetic energy reaches the maximum) at the bottom-most point. By the time it reaches the other end, its kinetic energy is completely converted into potential energy.
The process is repeated several times until the pendulum halts. Since some of the energy is lost in heat and friction, you need external energy to keep the pendulum moving.
2. Rock At The Edge Of A Cliff
Image credit: Shutterstock
Type: Gravitational Potential Energy
A rock sitting at the edge of the cliff possesses potential energy, which is proportional to the mass of the rock and height of the cliff. If you push it down the cliff, the same potential energy will be transformed into kinetic energy.
As you can see in the image, a heavy sandstone boulder rests precariously over a steep slope. It has potential energy relative to the slope, as it seems to be ready to fall at any moment and slide several meters into the valley below.
3. Water Behind Dams
Seli’š Ksanka Qlispe’ Dam
Type: Gravitational Potential Energy
The water behind the hydroelectric dam stores massive potential energy since it is at a much higher level than the water on the other side of the dam. When gates of such dams open, the water starts falling, and the stored potential energy is transformed into kinetic energy, which turns turbines to produce electricity.
Apart from generating electricity, water dams are also constructed for the purpose of controlling river flow and regulating floods.
4. Tree Branches
Type: Gravitational Potential Energy
Tree branches possess potential energy because they can fall to the ground. The heavier the branch and the higher it is to the ground, the more potential energy it has.
Similarly, a fruit hanging from the top branch also has some potential energy. As the fruit falls, its energy of position (potential energy) is transformed into the energy of motion (kinetic energy). And when it hits the ground, kinetic energy is converted into heat energy.
5. Roller Coaster
image Credit: Vecteezy
Type: Gravitational Potential Energy
Most roller coasters use gravity to move the cars along the track. A big chain (hooked to the bottom of the cars) pulls the cars to the top of the first hill, which is the highest point on a roller coaster. Once the cars reach the hill’s top, they’re released from chain and coast through the rest of the track.
Two forms of energy work in the roller coaster: potential energy and kinetic energy. One is converted into another throughout the ride, while a significant amount of energy is lost due to air resistance and friction.
The cars’ gravitational potential energy is least at the lowest point of the roller coaster and greatest at the highest point.
6. Spring
Type: Elastic Potential Energy
Energy stored in a compressible/stretchable objects is called elastic potential energy. The more an object can compress/stretch, the more elastic potential energy (U) it has. It is proportional to the spring force constant (k) and the string compress/stretch length (x) in meters.
When the spring is stretched or compressed, it gains a certain amount of potential energy. This is equal to the kinetic energy that was used to stretch or compress the string.
Once the string is released, the potential energy is again converted into kinetic energy. However, the energy conversion process is not fully efficient, since a significant fraction of energy is lost in heat and friction.
7. Bow and Arrow
Type: Elastic Potential Energy
The bow and arrow is a traditional ranged weapon system that consists of an elastic launching tool (bow) and long-shafted projectiles (arrows).
The archer uses his muscles to exert a force on the string, bending the limbs backward. The force he exerts on the string is known as ‘draw weight’. The elastic energy is now potential energy, which can be used to launch the arrow (by releasing the string).
The more you deform the limbs by pulling them backward, the more you increase the stored potential energy. Obviously, there is a limit to how much force you can apply to draw a bow and how much force the bow can withstand without cracking.
8. Stretched Rubber Bands
Type: Elastic Potential Energy
Have you ever been shot with a rubber band? If yes, then you know it contains enough energy to smack in the arm and cause a sting.
When you pull a rubber band, you input a certain amount of potential energy into it. And when you released it, this potential energy is quickly converted to kinetic (motion) energy.
9. Electric Circuit
Type: Electric Potential Energy
When we harness electricity to power circuits and gadgets, we are transforming energy from one form to another. Electronic circuits store (potential) energy and transfer it to other forms such as light, heat, or motion.
Just like objects under the influence of gravity have gravitational potential energy, charges in an electric field have electric potential energy.
The electric potential energy of a charge shows how much energy it contains. When set into motion by an electrostatic force, this stored energy becomes kinetic, and the charge does work (which is measured in Joules).
For any charge within an electric field, its electric potential energy is based on the type (negative or positive), amount of charge, and its position in the field.
10. The Food We Eat
Type: Chemical Potential Energy
The food we eat stores chemical potential energy. When it reaches our stomach, the same energy is transformed into other forms that our body utilizes.
As the bonds between atoms in food break or loosen, a chemical reaction takes place, forming new compounds. The energy generated from this reaction keeps us warm, helps us move, and grow. Different food contains different amounts of energy.
11. Dry Woods
Type: Chemical Potential Energy
Dry woods contain chemical energy. When they are burned in a fireplace, they release this chemical energy, which is eventually transformed into light and thermal (heat) energy. Following the chemical reaction, the wood is turned into a new substance: ash.
12. AA Batteries
Type: Chemical Potential Energy
Conventional batteries, such as a set of AA batteries, possess chemical potential energy, which can be converted into electrical energy.
Every battery is made of two electrodes (one cathode and one anode). Between these electrodes is the gel-like substance called an electrolyte. It consists of charged particles or ions that combine with electrode materials, generating chemical reactions that allow the battery to produce an electric current.
Different electrodes and electrolytes create different chemical reactions that determine the battery’s efficiency (how much energy it can store and its voltage).
13. Dynamite
Type: Chemical Potential Energy
Dynamite is another prominent example of chemical potential energy. It is made of nitroglycerin (a very unstable substance), sorbents (such as powdered shells or clay), and stabilizers.
When ignited, the nitroglycerin in the dynamite explodes quickly, releasing massive amounts of nitrogen and other gases along with heat.
Read: 8 Strongest Acids Ever Known To Us
14. Gasoline
Type: Chemical Potential Energy
When you fill your vehicle with gasoline, you are providing it with chemical potential energy. This energy is contained in various chemicals (mostly organic compounds obtained by the fractional distillation of petroleum) that makeup gasoline.
The energy is released when gasoline is burned in a controlled way in the vehicle engine. This potential energy release does two things: some of the energy is converted into work, which is used to move the vehicle, while some is converted into heat, which makes the vehicle’s engine very hot.
15. Nuclear Power Plants
Type: Nuclear Potential Energy
Nuclear potential energy is the potential energy of subatomic particles (like protons and neutrons) present inside the atom’s nucleus. It holds protons and neutrons together to form a nucleus.
When two or more atomic nuclei combine to form a large nucleus (nuclear fusion), a massive amount of energy is released. Similarly, when one nucleus splits into two smaller nuclei (nuclear fission), it releases large amounts of energy.
Nuclear power plants use such nuclear reactions (mostly nuclear fission of uranium and plutonium) to generate heat, which is then used in steam turbines to produce electricity.
Read: 10 Best Examples Of Kinetic Energy
Compared to other sources of energy, nuclear power plants use lesser amounts of raw materials, have zero-emission, and are more powerful and efficient.
