The Fundamental Difference Between Kinetic and Potential Energy

Energy is something that is at work everywhere around us all the time. This post gives the explanation and differences between kinetic and potential energy, the two types of energy.

Energy is Energy

At times, there is a wrong notion prevalent that kinetic energy is considered to be actual energy as opposed to potential energy, which is considered to have the ‘potential’ of being actual energy.

Energy is required to do any form of work. It is an abstract quantity which cannot be seen, but only the effects of which can be felt. The International System of Units (SI Units) of energy is ‘Newton-meter’ (N-m) or alternatively ‘Joule’.

In accordance to the ‘Law of Conservation of Energy’, energy can neither be created nor be destroyed; it can be converted from one form to another. The total energy of a system remains constant. Kinetic and potential energy are the two types of energy. Kinetic energy is associated with the motion of a body, while potential energy is associated with its position or the state that it is in. In physics, the term ‘potential energy’ was used for the first time by William Rankine.

Here, we shall compare the differences between kinetic and potential energy.

Potential Energy

This is the energy possessed by a body on account of its state or position. For a body at height ‘h’, having mass ‘m’, and where the gravitational acceleration is ‘g’, the potential energy is given as,

Potential Energy (P.E.) = m × g × h

Hence, the potential energy of a body is directly proportional to its mass, height, and gravitational acceleration. The gravitational attraction that acts on a body is the reason for the body to possess potential energy.

Examples

A ball placed on a table on the first floor of an apartment that has ten floors, on the fifth floor, and the tenth floor of the same building, will have potential energy. This energy, however, will not be the same in all the three cases, as even though the mass of the object remains the same, because its relative height keeps on varying.

Now, consider a ball, a book, and a pen that are placed at the same relative position from the point of reference. Despite being at the same relative height, the potential energy of the three will vary, because of the different mass that they have.

Kinetic Energy

Kinetic energy is the energy of a body due to its motion. This motion of the body can be in any direction. For a body with mass ‘m’ and speed ‘v’, the equation of kinetic energy is given as,

Kinetic Energy (K.E.) = ½ × m × v²

From the above equation, we can state that the kinetic energy of a body is directly proportional to its mass and squared value of its speed.

Kinetic energy is further divided into various forms like rotational, translational, vibrational, etc., or also in combination. In case of a system with multiple bodies, the kinetic energy possessed by them is due to the relative motion of the bodies present in it. Kinetic energy can be termed as the energy to do work for accelerating a body from rest to the desired speed. It is also the energy required to bring a body in motion to rest.

Examples

A vehicle traveling on the road will possess kinetic energy on account of the motion that it is in. Similarly, a ball rolling on the floor has kinetic energy owing to its rolling motion. An asteroid that is falling also has kinetic energy that can be attributed to the falling motion. In these examples, all the bodies have kinetic energies, but of varying values. This is due to the varying mass and velocities of these bodies.

Potential Energy Vs. Kinetic Energy

Applications of kinetic energy include generation of electricity by using the kinetic energy of waterfalls to rotate the turbines. Kinetic energy can be used to do work in various forms. Whereas, one of main applications of potential energy is to store energy. In order to do work, potential energy is converted into kinetic energy.