CBSE 8th Science- Chapter – Force and Pressure- Notes

CBSE-8-Force and Pressure-notes

What is force?

Push or pull on an object is called force.

Conditions for force to act:

At least two objects must interact for a force to come into play. Thus an interaction of one object with another object results in force between the two objects.

Resultant of Forces applied on an object:

Forces applied on an object in same direction add to one another.

If forces act in opposite direction of an object, the net force acting on it is difference between the two forces.

Strength of force is expressed by its magnitude and direction in which the force acts. If the magnitude or direction or both change, the strength of the applied force also changes.

SI unit for force is Newton and denoted by N.

So if more than one force are acting on an object, then the resultant force is the net force acting on it.

CBSE 8- Force and Pressure-notes
Resultant force when two or more force are acting on an object

Effects of force:

  1. Force applied on an object causes motion of the object
  2. Force applied on a moving object changes the speed with which the object is moving.

If the force applied on the object is in the direction of motion, the speed of the object increases. If the force applied on the object is in the opposite direction of the motion, then it results in decrease in the speed of the object.

That is, force brings change in the state of motion of an object

What is state of motion?

The state of motion of an object is described by its speed and the direction of motion

The state of rest is considered to be state of zero speed.

  1. Force of an object may change the shape of the object.

Kinds of force:

CBSE-8-Force and Pressure-notes
Kinds of force



Force acting on unit area is known as pressure.

Pressure= Force/ Area on which it acts

SI unit of pressure is N/m2 or Pascal(P)

As the area increases, pressure decreases.

Liquids and gases also exert pressure. Liquid and gases exert pressure in all directions, on the container, in which it is present.

Atmospheric pressure

The air around earth is known as atmosphere. This extends up to many kilometers above the surface of the earth. The pressure exerted by the atmosphere is known as atmospheric pressure.

Add a Comment

Your email address will not be published. Required fields are marked *