Quick summary: Kinetic and potential energy are inseparably linked. Here, we provide a definition for each type of energy, along with examples, and explain the relationship between the two.
On the surface, energy is a fascinating subject in physics that can be difficult to wrap our heads around. Scientists tell us energy can neither be created nor destroyed, but it can be altered. Potential and kinetic energy can be converted into each other.
What is Potential Energy (PE)?
PE is the stored energy in any object or system by virtue of its position or arrangement of parts. It depends on the object’s position in relation to a reference point. Simply put, it is the energy stored in an object that is ready to produce kinetic energy when a force acts on it.
If you stand up and hold a ball, the amount of potential energy it has depends on the distance between your hand and the ground, which is the point of reference here. The ball holds PE because it is “waiting” for an outside force—gravity—to move it.
What is Kinetic Energy (KE)?
KE is the energy of an object or a system’s particles in motion. When you drop the ball, gravity moves it from your hand to the ground. That movement is called kinetic energy. The KE of an object is relative to other stationary and moving objects present in its immediate environment. For instance, the KE of the ball you drop will be higher if you raise the ball higher.
It is also dependent on the velocity and mass of the person or the object. A larger person or ball moving faster has greater kinetic energy.
The Relationship Between Potential and Kinetic Energy
You now know that potential energy is position relative, and kinetic energy is motion relative.
The primary relationship between the two is their ability to transform into each other. In other words, PE transforms into KE, and KE converts into PE, and then back again. It’s a never-ending cycle in the science of physics.
Examples of Energy of Motion
Imagine you have a hammer in your hand. As you hold it, it has potential energy. As you bring the hammer down onto a nail, it has kinetic energy.
Now, the raised hammer has more PE since it has the potential to go higher or lower. When you hit the hammer on the nail, the potential energy is converted to kinetic energy. As soon as the hammer hits the nail, the energy changes into potential energy again.
Energy is neither destroyed nor lost during the whole process in this example—it’s only altered from one form to another, proving the law of conservation of energy.
The Wide, Wild World of Energy
[Innovation through ideas and inspiration ideas. Human hand holding light bulb to illuminate, idea of creativity and inspiration concept of sustainable business development.]
Here we provide some examples of the most common forms of energy to show the diversity in types of PE and KE. You may be surprised to learn about the broad range of fields involved.
What Is the Potential Energy of an Electron?
The correct answer: Everything in the universe is made up of atoms. Every atom has a nucleus around which electrons orbit. Since these electrons are constantly in motion, they have KE. But things change, albeit temporarily, when you apply pressure or energy to the atom.
You see, the KE of the electrons increases when pressure is applied, causing them to move faster, ultimately making them jump into a wider orbit. After this, every electron will have stored energy that will become its PE.
As this whole arrangement is temporary, the electron will release this sample of PE, converting it into KE while returning to its previously smaller orbit. This is also why the total energy of an electron is the sum of its PE and KE.
Is Electrical Energy Potential or Kinetic?
Electrical energy can be either potential or kinetic energy.
Electrical energy, broadly speaking, is the ability of the charged particles of an atom to cause an action. Electricity is the flow of electrical energy as electrons move between atoms. When the electrical energy is stored in an atom, that is potential energy. When the electrons are flowing, that is KE.
When you switch on a light, the electrical current travels down the wiring and is converted into light and heat, which by definition are both forms of KE as defined by the field of physics.
A battery is one of the best PE examples, as it is stored electrical energy. When you use a battery, the electrons flow out through a circuit, creating the kinetic energy that is electricity.
So by definition, the battery is all potential energy.
Is Sound Energy Potential or Kinetic?
Just like electrical energy, sound energy can be either.
Sound energy refers to the energy released by vibrating objects. These vibrations produce a wave that travels through a medium like air. Since the waves are vibrating the air particles that bring them to our ears, the waves themselves are kinetic energy. If something has the potential to make vibrations that would produce sound waves, that thing has sound potential energy.
For instance, when you play the drums, they vibrate. The vibrations pass to surrounding particles and then pass from one particle to another in waves. These waves oscillate and travel, creating KE at varying intensity. However, when the drums are left untouched, they have PE, since the equipment is not in use but has the capability to make noise.
Is Thermal Energy Potential or Kinetic?
Thermal energy is both kinetic and potential.
If you remember, the electrons of an atom have PE. Once you apply pressure to the electrons, they move rapidly, releasing thermal energy as heat.
Think of boiling water. Water, when placed on the stove, has PE. But once it starts to heat, the water molecules move faster, creating KE.
Thermal potential energy is PE at the atomic and molecular levels, when the particles show the potential of converting into KE. On the other hand, thermal kinetic energy is when the atoms and molecules start moving due to heat.
Is Radiant Energy Potential or Kinetic?
Radiant energy is KE created when electromagnetic waves travel through space. The sun is the biggest source of radiant energy on our planet.
The warm feeling you get once you step outside on a sunny day is the sun’s radiant energy touching your skin. More specifically, the electromagnetic waves make our skin’s molecules move faster, creating KE.
Potential Energy’s Role in Chemistry
Chemical potential energy is the energy stored in the chemical bonds of a substance. Various chemical reactions can release this energy. When chemistry teachers demonstrate a dramatic chemical reaction in the classroom, like a substance bubbling over, they do it so students learn that chemical energy is being released. The PE was stored in the substances being mixed, and the reaction turned it into KE. (It’s fun to watch, so the hope is the students will remember that for the test.)
Your Satisfaction is Our Priority
We're confident you'll love your plan, but if not, call us, and we’ll help you find the perfect plan without any extra cost.*
Gravitational Potential Energy
When a body of mass is brought from infinity to a point within the gravitational field of a larger mass without acceleration, the work done in displacing it from infinity (the point of reference) is converted into gravitational potential energy.
Picture a swimmer standing on a diving board at a pool. Gravity uses the diver’s weight to produce KE (the diving motion), which causes the diver to splash into the pool. So, a diver on the diving board has gravitational PE, which is then converted into KE when she dives into the pool.
Elastic potential energy
Elastic PE is stored in objects that can either be stretched or compressed. The more the object is stretched or compressed, the more elastic PE it has.
A good example is a stretched rubber band. The further you stretch it, the higher the elastic PE will be. Letting go of the rubber band creates one of the classic KE examples as it flies in the direction of its intended location. When it comes to rest, the elastic energy has become potential again.
Mechanical energy
A car parked at the top of a hill is an example of mechanical gravitational potential energy since the automobile has the capability to come down the hill. It’s the same with a roller coaster that halts at the highest point on the rails.
When an archer pulls a bow before taking aim, the pulled string has more mechanical elastic potential energy that is released in the direction of the target once the arrow is out of the bow.
Measuring Kinetic Energy and Potential Energy
PE depends on the force acting on the two objects, so its formula is:
PE = mgh
- m is the mass measured in kilograms
- g is the acceleration due to gravity
- h is the height in meters
KE is directly proportional to an object’s mass and the square of its velocity. The formula is:
KE = 1/2 m v²
- m is the mass measured in kilograms
- v is the velocity of meters per second
Energy Everywhere
Now you can see in simple terms just how indispensable and related these physics concepts are to our daily lives. From practical things like brushing your teeth to just standing, everything we do involves both forms of energy.
KE and PE also play a crucial role in making our earth greener, as they help create renewable energy sources like wind.
Energy is in everything. It isn’t ever lost—it only changes form.
Shopping for a electricity provider? Shop our residential electricity plans today.
Brought to you by justenergy.com
All images licensed from Adobe Stock.
