Different forms of energy are as given below:
There are many forms in which energy may be stored or displayed. The steam pressure in the boiler possesses energy because it moves the piston and ultimately does the work in moving the train.
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Petrol is a source of energy which moves cars at a high speed. Similarly, strong flow of water following down from a high mountain can be harnessed and its energy transferred into electrical energy capable of doing work in a number of ways.
All such forms of energy can finally be divided into two: Kinetic Energy and Potential Energy.
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1. Kinetic Energy:
Kinetic energy is the energy possessed by a moving body by virtue of its motion or this is the energy of a body in motion.
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For example, it is the energy of the rushing stream, wind pressing on the sails of the ship or the windmill.
Some examples of bodies possessing Kinetic energy in our day to day life are :
The Kinetic energy of running water is used to run the water mills, the Kinetic energy of a hammer is made use of in driving a nail in wood or a bullet fired from a gun can pierce a target due to its Kinetic energy.
To make it more simple, when a fast running car hits a big block on the road, the block is pushed from its place (though slightly) because of frictional force.
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The block moved and did work because energy was supplied to it by the moving car. It was Kinetic energy i.e., the energy that an object possesses by virtue of its motion.
(a) Increase in potential energy (b) Decrease in potential energy
2. Potential Energy:
By potential energy we mean stored energy or energy of position. In other words, Potential Energy is energy which is a body possesses by reason of its position, and which is capable of being transformed into Kinetic energy.
For example, the potential energy of water in dams is used to run turbines in order to produce electrical energy from generators.
We note here that water was stored (potential energy) and after it falls down it gained kinetic energy.
If falling down, it has gained kinetic energy, and so it is capable of doing work.
Due to the potential energy of the compressed spring in a loaded gun, the bullet is released with large velocity on firing the gun.
Thus a wound up spring possesses potential energy. In the process of winding up, the positions of the parts of the spring gets altered.
As they take their normal position the energy of the spring is released and changed into Kinetic energy.
Petrol vapour mixed with air possesses potential energy. When a spark explodes the mixture the potential energy is changed into the kinetic energy which moves the car.
Likewise due to the potential energy of the stretched bow, the arrow goes forward with large velocity when the bow is released. These are some more example of potential energy.