Broadly speaking, energy comes in two primary forms; Potential and Kinetic.
Potential energy is the energy stored in an object that is not in motion but is capable of becoming active. When stationary, every object has rest mass potential energy unless it is in a position to be affected by gravity and fall. It then possesses gravitational potential energy.
Potential energy is expressed as U.
Kinetic energy is the energy an object possesses due to its motion. A stationary object has zero kinetic energy and only gains it as it moves.
The kinetic energy of an object remains consistent unless its speed changes.
Types of Kinetic Energy
There are five main types of kinetic energy:
Radiant Energy
Radiant energy travels in electromagnetic waves and particles through space. They may, or may not be visible to the naked eye. This includes visible light, x-rays, gamma, UV, radio, and microwaves.
It is generated through electromagnetic waves and humans usually experience it via heat.
Radiant energy moves in straight lines through space and matter. It travels at speeds of 299,792,458 m/s.
Other examples of radiant energy:
Sunshine – Both heat and light travel in the sun's rays.
Solar power – Solar energy converts radiant energy from the sun into electrical energy.
Incandescent light bulb - Both the visible light and the warmth that a bulb emits are types of kinetic energy.
Electric toaster – The internal elements heat up, creating radiant energy to warm and toast bread.
Radio signals – Information is transferred over vast distances as radiant energy. It travels in waves; this motion is a form of kinetic energy.
Some materials absorb radiant energy before re-emitting it as fluorescent light.
Thermal Energy
Although similar to radiant energy, thermal energy relies on the atoms and molecules of a body or system to function, and not waves and particles.
Heat energy is generated as the temperature increase which causes the atoms to move faster than usual and collide with each other.
Even if you can't see the energy, you will feel it on on your skin in the form of warmth.
Geothermal energy is generated heat stored in the earth. It originates from the formation of the planet and from radioactive decay of materials. It is stored in the earth's crust and relies on thermal energy as the energy to determine temperature.
This energy can be harnessed and converted into electrical energy.
Good examples of geothermal energy are volcanic eruptions and geysers.
The geothermal energy of the earth heats underground water and generates steam. The water molecule's motion increases, causing them to collide and build up excessive pressure.
The steam will finally burst through the ground, creating a geyser.
Boiling water is the perfect example of thermal energy as it can be seen as well as felt. Water at a rolling boil on a stove has kinetic energy; the minute water molecules are extremely active.
Oven baking - Molecules with cold and frozen food collide ever faster as food gets to its optimum temperature
Sun heats the atmosphere which raises daytime temperatures. You can feel the energy as warmth on your skin.
Fans of the outdoor life experience many forms of thermal energy, including hot springs, heated swimming pools, and mugs of hot chocolate around a campfire.
Sound Energy
Sound energy is the movement of energy in waves. It is generated by vibrations and needs a medium, such as air, water, or a solid to travel through.
It is produced when sound waves move outwards from a vibrating object or sound source.
The energy in sound is far less than in any other form of energy as sound waves progressively lose their energy the further they travel.
Voices are the perfect example of sound energy, whether they are whispering, talking, shouting, or singing.
Human movement such as clapping, jumping, skipping, and stamping create sound waves and, in turn, sound energy.
Music, whether that be from an orchestra, a concert, or a stereo. All musical instruments rely on vibrations to create sound energy. Drum skins, the reeds of woodwind instruments, and striking percussion create vibrations through mediums.
Animal noise such as bees buzzing, horses neighing, and sheep bleating are examples of kinetic energy through sound waves.
Sonic booms generate an enormous amount of sound energy. Anything that moves through the air faster than the speed of sound creates these thunder-like, deafening claps of sound.
Electrical Energy
Every single object is made up of atoms, atoms are tiny particles made up of electrons, protons, and neutrons. Electrical energy is created when electrons flow along a circuit. Humans force movement of the electrons by magnetic forces called conductors. As the electrons move from 1 atom to another, an electric current is created which generates electricity.
Batteries transfer stored chemical energy as charged electrons through a wire.
For example, electrical energy is transferred from an outlet to a lamp and presents as light and thermal energy.
Lightning is an excellent example of electrical energy in nature, energy too powerful to be restricted by a wire.
Thunderclouds build up huge amounts of energy called static electricity. This gets released as lightning strikes when the clouds collide against each other.
Household devices and appliances that operate using an AC (Alternating Current) or DC (Direct Current), depending on their configuration, are further examples of electrical energy.
Hydroelectric dams combine multiple energy sources to transform the kinetic energy from flowing water into electrical energy.
Similarly, wind turbines harness energy from the wind to generate electrical energy.
The human body relies on ATP as its primary energy carrier. Adenosine Triphosphate is the stored energy from broken-down food and light. ATP is converted into electrical energy which sends a charge through our nervous system cells to maintain a consistent heartbeat.
Electric eels have 2 organs that function in a similar manner to batteries. They are able to generate shocks of up to 500volts – enough to kill a human!
They have 3 sets of internal organs and a series of special cells called eloctrocytes.
This is where the fish makes both high and low voltage electricity.
Mechanical Energy
Mechanical energy is the energy stored in objects and is the sum of their kinetic and potential energies.
Kinetic – Anything in the machine or system that is moving.
Potential – Anything in the machine or system that is stationary but has stored energy.
Potential energy can be broken down further:
- Chemical Potential – Energy that's stored in the chemical bonds of a substance.
- Gravitational Potential – Energy as a result of the position/height of an object.
- Elastic Potential – Energy stored in a stretched elastic or coiled spring.
Mechanical energy cannot be created or destroyed but instead converts into a different energy form.
The quicker an object moves, the more energy is generated and stored.
The wind is mechanical energy. Its natural movement is captured by turbines and converted into electrical energy. Hydroelectric dams use the mechanical energy of flowing water to convert into electrical energy.
A fired bullet employs mechanical energy until it hits its target and transforms its energy into heat.
An internal combustion engine works when chemical energy converts into mechanical energy by burning fuel. This is how the vehicle is set in motion.
Playing the piano is another example. The fingers use mechanical energy to do the work. This transfers to the hammer where more mechanical energy is used to make them strike the note. The result is beautiful music, which we hear as sound energy.
Almost everything kids do outside uses mechanical energy. Jumping on a trampoline, running, jumping rope, sliding down a slide, kicking a ball, and throwing a Frisbee are all examples of the combination of kinetic and potential energy.
Satellites that orbit the earth, and the planets around the sun all do so because of mechanical energy.
A plane in flight and skydiving from that plane are further examples of kinetic energy in its mechanical form. Mechanical energy provides the thrust that increases the speed of the airplane. As it goes faster, the energy converts to kinetic. As the plane climbs to a higher altitude the energy converts to gravitational potential energy. The skydiver has maximum potential energy before the jump, once they leave the plane the increasing velocity is where they experience kinetic energy.
Final Thoughts
All types of kinetic energy involve movement and motion.
Each type is not exclusive, for instance, an illuminated bulb uses electrical energy to produce radiant and heat (thermal) energy, as does a toaster.
