Types of Potential Energy

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. We shall formulate gravitational energy with the following example.

• Consider an object of mass = m.
• Placed at a height h from the ground, as shown in the figure.

As we know, the force required to raise the object equals m×g, that is, the object’s weight.

As the object is raised against the force of gravity, some amount of work (W) is done on it.

Work done on the object = force × displacement.

So,

W = m×g×h = mgh

Above is the potential energy formula.

As per the law of conservation of energy, since the work done on the object is equal to m×g×h, the energy gained by the object = m×g×h, which in this case is the potential energy E.

E of an object raised to a height h above the ground = m×g×h

It is important to note that the gravitational energy does not depend upon the distance travelled by the object, but the displacement, i.e., the difference between the initial and the final height of the object. Hence, the path along which the object has reached the height is not considered. In the example shown above, the gravitational potential 

 energy for both blocks A and B will be the same.

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 elastic its potential energy is. 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
• A bent diver’s board just before a diver dives in
• The coil spring of a wind-up clock

An object that stores elastic potential energy will typically have a high elastic limit. However, all elastic objects have a threshold to the load they can sustain. When deformed beyond the elastic limit, the object will no longer return to its original shape.

Elastic potential energy can be calculated using the following formula:

\(\begin{array}{l}U=\frac{1}{2}kx^2\end{array} \)

Where,

• U is the elastic potential energy
• k is the spring force constant
• x is the string stretch length in m