Forces

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Observe the following pictures. Some kind of force is needed for an object to move or to change shape or to change its position.Force is also needed to change the speed or direction of a moving object.

1. Muscular force:

2. Mechanical force:

Types of forces

The force applied using parts of the body like arms or legs is called muscular force. Eg. While playing cricket or football, players apply muscular force on the ball. Force applied through the use of animals like bullocks, horses, elephants is also muscular force.

Force applied by using machines is called mechanical force. eg. This type of force is used in most of the commonly used machines like pump or vehicles like tractors etc.

3. Gravitational force:

Force applied by the earth is called gravitational force. Gravity acts on every object. Any object thrown upwards reaches a certain height and then falls down. It happens because of gravity. As a result of gravity, the motion of an object thrown upwards gradually decreases and eventually becomes zero; after that it begins to fall downwards.When we lift something we have to apply force against gravity. The greater the mass of an object, the greater is the force of gravity acting on it.

4. Magnetic force:

The force exerted by a magnet is called magnetic force.

Eg. In some goods yards, there are cranes with magnets. These are used to lift heavy loads.

The maglev train – Magnetic levitation (maglev) - Scientists have designed a train which gets lifted up above the tracks and travels with very high speed in air. (500-580 km per hour). It is based on the principle of magnetic repulsion between like poles of a magnet.

5. Frictional force:

A certain force acts between a moving object and the surface along which it moves. This force is called friction. Friction always acts in a direction opposite to the motion of the body. Friction between different surfaces is different.

eg. Can you walk on a greasy floor? No. Because there is no friction, you can not walk on it. But the same grease helps your vehicle work smoothly.Have you observed ramps of the shopping mall or airport are purposely made rough so that people won’t slip while walking? On the other hand, surface of the ‘slide’ in the park is made very smooth so that you can slip quickly on it.Presence and even absence of friction play important role in different situations.

5. Static electric force:

Spread small pieces of paper on a table. Rub a plastic comb on dry hair. Bring both the things close to each other. What do you see? Pieces of paper move close to the comb. Rubbing causes electricity to develop on substances like rubber, plastic and ebonite. This force that is electricity produced due to friction is called static electric force. This force is weaker than other types of force. It is obtained by rubbing a particular substance on one another.

No. Action Force applied

1 Sprinkling talcum powder on a carom board.

2 A potter turning his wheel

3 Ball bearings in machines

4 Applying brakes on a bicycle

Activity

Visit a nearby garage. Observe different activities happening there like oiling a vehicle, repairing etc. Observe and study different forces used in different parts of a vehicle.