Kinetic and Potential Forms of Mechanical Energy?

To understand the concept of energy, consider a ball rolling on the ground. If you apply a force to the ball and increase its rolling speed, you are actually doing work on the ball which results in an increase in the ball’s energy.

There are many different forms of energy including mechanical, chemical, electrical, nuclear and thermal energy.

While there are many types of energy, Mechanical Energy has two fundamental forms, potential and kinetic.


Potential Energy

Potential energy is defined as the energy that an object possesses by virtue of its position.  To better understand the concept of potential energy, assume that you want to move a chair three floors up the stairs in your building. As you carry the chair and move it up the stairs, you will be doing work against gravity because you are carrying the chair to a higher floor (and hence to a higher altitude). In other words, the potential energy of an object is directly related to the altitude at which this object is located. 

The potential energy of an object is directly related to the mass of the object and to the altitude at which the object is located at a given moment. This means that a heavier object will have a greater potential energy, and the same object placed on a higher altitude will have a greater potential energy than if it was placed on a lower altitude.

Assume that you drop the chair out the window from the third floor, what do you think will happen to the chair’s potential energy? When the chair is dropped out the window, its potential energy will be converted into kinetic energy because the chair will be in a vertical free fall motion until it hits the ground. Using the laws of physics, you will be able to calculate the final speed of the chair before it hits the ground, as well as the time required for the chair to hit the ground.


Kinetic Energy

Kinetic energy is also known as “the energy of motion”. It is the energy capable of moving another object by its own movement. If you are driving your car at 40 km/hour then decide to accelerate to 80 km/hour, you would have also increased the kinetic energy of your car.


Conservation of Total Energy and Mechanical Energy

Energy can neither be created or destroyed.

Energy can change form from one type of energy to another, however when it does so it is without any net gain or loss.  This is known as conservation of energy.

This can be applied with a system regardless of the size of the system.  As long as the system is closed the amount of energy within the system will remain the same over time.

When we talk about the conservation of mechanical energy this applied to idealised systems which contain only kinetic and potential energy and in which we assume that no energy is lost to friction or other effects.