Force, work, power and energy

Potential Energy

So, you will learn that -
Potential energy possessed by a body by virtue of its configuration is known as elastic potential energy.

Potential energy possessed by a body by virtue of its position with respect to the ground is known as gravitational potential energy.

A body possesses potential energy by virtue of its configuration or position.

Where does a keyed toy car derive energy to move?

Take a rubber ball and go to the top floor of a building. Now, drop the ball from a height onto the floor where you are standing. The ball will rebound to some height. Observe the height of the rebound. Now, drop the ball onto the ground below and again note the height of rebound of the ball.

You will observe that the ball rebounds to a greater height when dropped on the ground than when it is dropped on the floor where you stand. This is because the energy of the ball while hitting the ground is greater than its energy while hitting the floor. From where does the ball get this large amount of energy?




We know the fact that any object located at a height with respect to a certain reference level is said to possess energy called gravitational potential energy. This energy depends on this reference level (sometimes also referred as ground level or zero level). When a ball is taken to the top floor from the ground floor, it acquires some gravitational potential energy. When this ball is dropped from a height h1 onto the top floor, the zero level is the top floor itself. When the ball is dropped from a height h2 onto the ground, the zero level is the ground. Since the distance covered by the ball is greater in the second case, i.e., h2 > h1, it rebounds to a greater height in the second case.

Hence, we conclude from the above discussion that the potential energy stored in a body is directly proportional to its height with respect to zero level.

Formula for gravitational potential energy

The gravitational potential energy of an object is equal to the work done to raise it through a height from the ground.

The gravitational potential energy of water stored in a dam is used for generating electric energy in a hydropower plant.