Basically, we eat food and do some kind of different work. We say that young has more energy than the old ones.
It redirects that if a person can do more work it means he has more energy.
Hence, the Capacity of doing work is called energy.
The energy of a body is numerically equal to the amount of work which the body can do.
The SI unit of energy is similar to that of the work, it is joule. For example, if a body can do 20 joules of work, we say that the body possesses 20 joules of energy. Whenever work is done, an equal amount of energy is spent.
There are several ways of energy.
The energy acquired by a body has different names depending on how this energy has been acquired.
1. Mechanical energy
Mechanical energy is the energy possesses by a moving body or the body resting at a certain height above the surface of the earth.
It has two forms, i.e. kinetic energy and potential energy.
a. Kinetic energy
Kinetic energy is the energy possesses by a body by the quality of its motion.
A moving hammer drives a nail into wood because of its kinetic energy.
For example, a bullet fired, a stone left from a catapult, wind, flowing water, rolling stone, etc. have kinetic energy.
If a body having mass (m) is moving with a velocity (v), its kinetic energy will be given by,
Kinetic energy = 1/2 mv^2
From relevant relation, we can determine,
- The kinetic energy of a body is directly proportional to the mass of the moving body. It means that if the mass of a moving body increases by any time the kinetic energy increases by the same times.
- The kinetic energy of the body is directly proportional to the square of the velocity of the body. It means that, if velocity increases by any time, the kinetic energy increases by the square times of the velocity change.
b. Potential energy
Potential energy is the energy possessed by a body by the quality of its position or configuration.
For example, a stretched bow, a stretched catapult, a compressed spring, a stone raised up to a certain height, the water stored in a dam, etc. have potential energy.
The gravitational potential energy of a body of a mass m when placed at a height h from the ground level is given by,
Potential energy = mgh
Where m = mass
g = acceleration due to gravity
h = height from the earth’s surface.
From the relevant equation,
we can determine that potential energy is directly proportional to mass (m), acceleration due to gravity (g) and height (h) lifted from the surface.
If any one factor among them increases by anytime, the potential energy also increases at the same time.
Note- The sum of potential and kinetic energy is known as mechanical energy.
2. Electrical energy
The continuous flow of electrons in a particular path is called possession of electrical energy.
Sources- dynamo, battery, hydropower station, etc.
3. Heat energy
It provides a sensation of warmth and makes transference of higher temperature to a colder body.
Source- sun, coal, gas, etc.
4. Light energy
By using light energy we can see different objects when the light comes on an object it reflects into our eye that’s how we see an object.
Source- solar heater, solar cooker, solar cells, etc.
5. Sound energy
The vibration of molecules of a body possesses sound.
Source- Ringing bell at our homes.
6. Magnetic energy
The energy that is present in the magnet whose effect we can feel on the magnetic bodies is magnetic energy.
A magnet attracts small pieces of iron when it comes closer to any magnetic substance. like, iron.
magnetic substance is use mainly in factories to lift heavy weights of magnetic bodies and uses to separate iron pieces from waste materials.
Source- radio, telephone, telegraph, etc.
7. Chemical energy
The energy which is stored and released from it when a chemical change takes place is called chemical energy.
In this energy new substance is gain after a chemical reaction. For example, the burning of the match stick gives heat and light.
8. Nuclear energy
The process of splitting of a heavier nucleus of an atom into smaller nuclei of atoms or forming of having a nucleus of an atom from smaller nuclei of an atom is nuclear energy.
purpose- for making atom bombs.
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