CBSE | NCERT Solutions for Class 8 Science-Force and Friction
Class 8 science – Chapter 10 Force and Friction : In this article, we will discuss the Force and Friction from 8th Class Science.
The 8th Class student must have noticed that kicking a football will change its position. A push or pull acting on an object is called Force. The SI unit of force is the Newton (N).
Force can make a stationary object move or make a moving object move faster.
Force can slow down or completely stop a moving object– A moving toy car can be made to stop by applying a force. In order to stop or slow down a moving body, we need to apply force in a direction opposite to the directions of motion of the moving body.
Force can change the direction of a moving object– Force changes the direction of a moving object.
Force can change the shape or size of an object– While making Chapattis we change the shape of the dough by applying force with our hands. Materials that break easily when we apply a force are termed brittle.
Magnitude of Force
The magnitude of a force is the strength of the force acting on an object. It depends upon on the number of forces involved in a particular action.
- When two or more forces act in the same direction, then the magnitude of the force on the object is the sum of the forces.
- When two or more forces act in an opposite direction, then the magnitude of the force on the object is the difference between the forces.
- If the magnitude of the force on object changes, the effect of the force will also change.
Now we will discuss Classification of forces as per Class 8 Science.
Classification of Forces
The force acts on an object only when the force is in contact with the object, these forces are called contact forces. Some forces can act on objects without physical contacts are called non-contact forces.
Forces that do not need physical contact with the object on which they are acting are called non-contact forces.
The force with which objects pull each other is called gravitational force. This force is very small and we can feel it only if an object is very massive. Different objects exert different magnitude of the gravitational force.
The earth is much larger than us and exerts a gravitational force on us that is strong enough to keep us bound to it
Example- Gravitational force makes the earth move around the sun and also makes the moon go around the earth.
The force between electric charges is called electrostatic force.
Let’s discuss an example for 8th Class students. If we will rub a plastic comb with hair and bring it close to tiny bits of paper, the bits of paper get attracted to the plastic object. This example demonstrates the electrostatic force.
Tiny particles of dust and smoke can also be attracted by electrostatic forces. This method is used in electric air purifiers and in factories to purify air in chimneys before escaping to the atmosphere.
The force exerted by magnets on each other and on metals such as iron, cobalt, and nickel is called magnetic force. The magnet attracts iron, so they are used to separate waste iron objects and scrap iron from garbage dumps so that they can be recycled.