Lesson 3: Potential energy and kinetic energy

Potential energy as a form of energy that results from the alteration of its position or state.  In other words, potential energy is energy that is stored, or not yet used.

In the case of a bow and an arrow, when the bow is drawn, it stores an amount of energy, which is responsible for the kinetic energy it gains when the arrow is released.

Similarly, in the case of a spring, when it is stretched from its original position, it gains energy which we observe in the form of stress we feel in our hands when we stretch it. 

Types of Potential Energy

Potential energy is one of the two main forms of energy. There are two main types of potential energy, and they are:

• Gravitational Potential Energy
• Elastic Potential Energy

Gravitational Potential Energy

The gravitational potential energy of an object is defined as the energy possessed by an object that rose to a certain height against gravity.   So, in figure 2, the books have gravitational potential energy because they are at height on the table. 

Elastic Potential Energy

Elastic potential energy is stored in objects that can be compressed or stretched, such as rubber bands, trampolines, and bungee cords. The more an object can stretch, the more potential energy it has. Many objects are specifically designed to store elastic potential energy, such as the following:

• A twisted rubber band that powers a toy plane
• An archer’s stretched bow

An object that stores elastic potential energy will typically have a high elastic limit. When deformed beyond the elastic limit, the object will no longer return to its original shape.

When an object which has gravitational potential energy or elastic potential energy, it can be converted into kinetic energy.  Remember that kinetic energy is the form of energy an object has when it is moving.