Forms of Energy

Forms of Kinetic Energy

Examples of Kinetic energy in everyday life, kinetic energy is perhaps the most often observed form of energy and the most intuitive to humans, StudySmarter Originals

Kinetic energy depends on two factors. The mass of the object and the velocity at which it's moving.

$E_K=\frac{1}{2}m{v}^2$

$\mathrm{Kinetic}\mathrm{energy}=0.5\times \mathrm{mass}\times {\mathrm{velocity}}^2$

Where$E_k$is the kinetic energy in joules$\left(\mathrm{J}\right)$,$m$is the mass in kilograms$\left(\mathrm{kg}\right)$and$v$is the velocity in metres per second$\left(\frac{\mathrm{m}}{\mathrm{s}}\right)$.

Recall that we can apply an external force to accelerate an object. When this happens, we say that work was done over the object.

Doing work on an object changes its kinetic energy. Therefore, we can calculate work as the change in kinetic energy.

$W=\Delta E_K$

or in words

$\mathrm{Workdone}=\mathrm{change}\mathrm{in}\mathrm{kinetic}\mathrm{energy}$

It takes the same amount of work to bring a body to a specific speed as to stop once it is moving at that speed. However, the work done will be negative in the latter case because the force has to act against the object's motion.

There are two types of kinetic energy:

An object moving in a straight line has translational kinetic energy

A spinning object has rotational kinetic energy.

Let's now look into heat energy which is also related to kinetic energy.

Heat energy

Heat or thermal energy is produced due to the motion of atoms. In other words, it is the kinetic energy of atoms, molecules, or ions. Heat transfer always happens from a point of higher temperature to another of lower temperature. There are 3 ways of transferring heat between two bodies: conduction, convection, and radiation.

Other forms of Kinetic Energy

• Sound energy - Sound waves transfer energy throughout the air molecules as vibrations or kinetic energy of the air molecules.

• Radiant energy or Light energy is released when photons dissipate energy into the surroundings. It travels as electromagnetic radiation. An energy transfer occurs when the light comes in contact with an external surface - for instance, photosynthesis in plants and light falling on solar panels.

We now have a clear idea of how an object that moves has kinetic energy. Now, let's look at how an object can store energy.

Forms of Energy: Potential Energy

When someone says that they have potential, it means they have the capacity to do something thanks to their innate abilities. A similar logic applies to potential energy.

Potential energy is stored energy that can be released to work or increase kinetic energy. There are different types of potential energy. Let's go over a few of them.

Gravitational Potential Energy

You may have noticed that a rock causes a bigger splash when dropped into the water as we release it from a greater height. When we elevate an object in a gravitational field, it gains gravitational potential energy (GPE). The higher we raise the rock, the more potential energy it acquires. Then, when we drop it, this potential energy converts into kinetic energy as the rock falls.

An object's gravitational potential energy depends on its height, the strength of the gravitational field it is in, and the object's mass.

$E_P\mathit{=}\mathit{}mgh$

or in words

where$E_P$is the gravitational potential energy in$\mathrm{joules}\left(\mathrm{J}\right)$,$m$is the mass of the object in$\mathrm{kilograms}\left(\mathrm{kg}\right)$,$\mathrm{h}$is the height in$\mathrm{meters}\left(\mathrm{m}\right)$, and$g$is the gravitational field strength on Earth$(9.8\mathrm{N}/\mathrm{kg})$.

The change in the potential energy of a system defines the work done over it.

$∆E_P=W$

or in words

$\mathrm{Change}\mathrm{in}\mathrm{gravitational}\mathrm{potential}\mathrm{energy}=\mathrm{Work}\mathrm{done}\mathrm{to}\mathrm{lift}\mathrm{the}\mathrm{object}$

Chemical Potential Energy

This energy is transferred when the bonds break during chemical reactions. Common examples involving the transfer of chemical energy are:

• The combustion of coal converts the chemical energy into heat and light.

• Batteries store chemical energy, which is converted into electric energy.

• Leaves convert the sun's energy into chemical energy.

Elastic potential energy

Mechanical energy

So then what is mechanical energy?

It is given by the following equation:

$E_{\text{mechanical}}=E_P+E_K$

or in words

$\mathrm{Mechanical}\mathrm{energy}=\mathrm{Potential}\mathrm{energy}+\mathrm{Kinetic}\mathrm{energy}$

Examples of Energy Transfer

Whenever the state of a system changes, energy transfers from one state to another. Energy can be transferred in different ways:

• Mechanical energy transfer
• Electrical energy transfer
• Thermal energy transfer
• Radiation energy transfer

Let's work on a few examples that will test your understanding of the concepts we covered in this article.

What about the energy conversions when an object is falling? let's find that out using our next example.