Conservation of Energy with Examples

Law of ‘Conservation of Energy’ explained with real life examples. Law of ‘Conservation of energy’ is applicable in our daily life as we convert one form of energy to another to do work.

Let us start by understanding work and energy. Both living and non-living things do work. A cat runs behind a mouse; a bus moves on the road. The cat and bus are doing work. To do work, energy is needed.

What is Energy ?

Energy is defined as the ‘capacity to do work’. The cat gets energy from food and the bus from gasoline. When the cat and the bus move, they have kinetic energy. So chemical energy from food and gasoline is converted to kinetic energy.

What are different types of Energy ?

The different types of energy are Chemical energy (from chemical bonds), Thermal energy (from heat), Solar Energy (from Sun), Nuclear Energy (from atoms), Kinetic energy (energy in motion), and Potential energy (energy from relative position).

Energy conversion: is the process of converting one form of energy to another form. For example, on a cold night, we rub our hands together to keep ourselves warm. Here, kinetic energy from the rubbing of hands is converted to thermal energy.

What is Conservation of Energy ?

Energy can neither be created nor destroyed, but can only be transformed or transferred from one form to another. For example, Solar cell panels do not create energy but harness solar energy and convert it into electrical energy. Further, electrical energy can be converted into light and heat energy in our homes. So, energy changes forms but the total energy will remain the same in an isolated system.

Understanding Conservation of Energy with an experiment

Swing a pendulum and mark its positions. The extreme ends of the movement are labeled as A and B and the midpoint as C.

First, the ball is pulled to A from C. The K.E (Kinetic Energy) from our hand is converted into P.E (Potential Energy) and transferred to the ball. So, at position A, P.E = maximum; K.E = 0 on the ball. Now, the ball moves from A to reach C by converting its P.E to K.E. At C, P.E = 0; K.E = maximum on the ball. As the ball has high kinetic energy, it will automatically move forward to B. At B, all the kinetic energy is converted to potential energy. As a result, P.E = maximum; K.E = 0 on the ball. The ball momentarily pauses at B as the K.E = 0. But at this point, the stored P.E again gets converted to K.E making the ball move in the opposite direction. However, the ball collides continuously with air molecules, losing its P.E and K.E to the air molecules. The ball will eventually come to rest.

In contrast, in outer space there is no atmosphere and so there would be no collision between the ball and air molecules. There would be no loss of P.E and K.E and the swinging process would continue forever.

The swinging of the ball in outer space behaves like a closed system, following the boundaries of Conservation of Energy.

Examples of energy conversion

1. The conversion of chemical energy in food to mechanical to ride a bicycle.
2. The conversion of solar energy to chemical during photosynthesis in a plant.
3. The conversion of chemical energy stored in gasoline to mechanical energy to run a car.
4. The conversion of electrical energy into heat energy by in-room heaters.

What is Sustainable Energy ?


Certain energy conversions provide clean energy without polluting the atmosphere. Such energy conversion is called sustainable energy. The conversion of the kinetic energy of the wind to electrical energy to light our homes is clean energy. The conversion of solar energy to electrical energy is another example of sustainable energy.

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