Category : 4th Class
Force, Work and Energy
Whenever we push or pull an object, we apply force. A force can make an object move, can stop a moving object, can change direction of a moving object and can change the shape of an object.
Types of Force
There are different types of forces:
Muscular Force the force exerted by muscles of our body. For example, lifting a bucket, lifting dumbbells, etc.
A Man lifting a dumbbells
It is the force exerted when an elastic material is stretched. For example, stretching of rubber band.
Stretching a rubber band
It is the force exerted by two surfaces on each other in moves over the other, while they are in contact. For example, while walking on a road frictional force is acting between the road and the sole of our shoe.
Friction, between shoes and Floor
The force exerted by the centre of the earth which pulls objects towards it. For example when a ball is thrown in the air, it comes back towards the earth due to gravitational force, an apple falling from a tree, etc.
Falling of an apple due to gravitational force
When we rub a comb through dry hair, the comb gets charged and is able to attract tiny bits of paper. The force exerted by charged comb on the bits of paper is called electrostatic force.
Charged hairs exert force on balloon
Work refers to an activity that involves applying force on an object and movement the object in the direction of the force. For example, if a man lifts a bucket then some work is done. In this case, due to the force applied by the man, the movement bucket takes place in upward direction.
Simple Machines tools which make our work easy are called simple machines. For example, pulley, wheel and axle, lever, inclined plane, etc.
Energy is the capacity or ability to do work. Energy can be of various types.
This is the energy of motion that does some work. For example, wind turns a windmill.
Heat energy is produced when a fuel is burnt in the air. For example, when coal is burn in the air, heat energy is produced. Heat energy is used in steam engines, in cooking, etc.
The energy obtained by splitting of an atom. This energy can also be used to produce electricity.
The energy, we get from electricity, is called electrical energy. We use electrical energy in different ways, for example, we use electrical energy to light our house to watch TV, for running refrigerator, etc.
This energy is due to the earth's gravitational pull.
Sources of light such as sun, bulb, tubelight give light energy.
Sun is a source of light energy
Radio, televisions, music systems are sources of sound energy.
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