Force, work and energy
Force
If you push something, it will move and things also show movements if you pull them.
To move something, we require pulling or pushing it.
This push or a pull is called a force.
Kinds of forces
If you push the toy-car on a carpet, its speed decreases. After a while, it stops. The force that makes it to slow down is known as the force of friction. Friction is produced because of the rubbing of the toy- car friction. Friction is produced because of the rubbing of the toy –car against the rough surface of the carpet. But see that the car goes further on being pushed on a smooth floor. On the smooth surface, the force of friction is less.
When you throw a ball upwards it falls down after reaching a particular height. This occurs because of a force called gravity acting on it. This force pulls the ball down. It is to be noted that gravity acts on every object on the earth this is the reason that anything that you throw up, comes
Work
When some movement is made, this is called work is done. You can easily push a chair but it will be difficult for you to push a cupboard, full of books. For moving the cupboard, you have to use more force. This means that more work is done in moving the cupboard than moving the chair.
Energy
Energy is the ability to do work. You require energy for running, for playing or for pushing a chair. A car needs energy for moving. Wind requires energy so that it can sway the trees. Energy is also needed for changing matter. Cooking of the food needs energy, changing water to vapors needs energy. There are different forms of energy.
The following are the important forms of energy:
Light energy
Plants use light energy of sunlight for preparing food.
Electrical energy
You do a lot of things at home by using the energy of electricity. This form of energy is used for heating and lighting. The electrical energy is used to run electrical gadgets such as computers, refrigerators, air conditioners, fans, television etc.
The main sources from where you get energy are as under
The sun
The sun is said to be the main source of energy for human beings. It gives you heat and light energy. The light energy of sun is used by plants for preparing food for all thing beings. You get energy to work when you eat this food in this way; all living beings depend on the sun to get the energy they need.
Moving water and air
Moving water and air contain energy. This type of energy is mainly used for generating electricity.
A river dam uses the power of flowing water for generating electricity. In a windmill, the power of wind is used for generating electricity.
Fuels
Fuels are excellent sources of energy. The examples of fuel are coal, oil, gas or petrol. They energy is stored in the fuel. You can release this energy if you burn them. This energy is used for running machines, cars, heating homes, cooking and for a lot of other purposes.
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