In our daily life there has many actions like picking, opening, shutting, kicking, hitting, lifting, flicking, pushing, pulling are often used to describe certain tasks. Each of these actions usually results in some kind of change in the state of motion of an object.
So, a push or a pull on an object is called a force.
Suppose the man now begins to push the car, due to the interaction, a man interact with the car. Means at least two objects must interact for a force to come into play. Thus, an interaction of one object with another object results in a force between the two objects.
Forces applied on an object in the same direction add to one another. If the two forces act in the opposite directions on an object, the net force acting on it is the difference between the two forces.
A force could be larger or smaller than the other or equal to each other. The strength of a force is usually expressed by its magnitude. Also, if the direction or the magnitude of the applied force changes, its effect also changes.
A force applied on an object may change its speed. If the force applied on the object is in the direction of its motion, the speed of the object increases. If the force is applied in the direction opposite to the direction of motion, then it results in a decrease in the speed of the object.
The application of force on an object may change its shape. While a force may cause one or more of these effects, it is important to remember that none of these actions can take place without the action of a force.
When we push an object like a school bag or lift a bucket of water, where does the force come from This force is caused by the action of muscles in our body. The force resulting due to the action of muscles is known as the muscular force.
Animals also make use of muscular force to carry out their physical activities and other tasks. Animals like bullocks, horses, donkeys and camels are used to perform various tasks for us.
A muscular force can be applied only when it is in contact with an object, it is also called a contact force.
The force responsible for changing the state of motion of objects in all these examples is the force of friction. It is the force of friction between the surface of the ball and the ground that brings the moving ball to rest.
The force of friction always acts on all the moving objects and its direction is always opposite to the direction of motion.
A magnet can exert a force on another magnet without being in contact with it. The force exerted by a magnet is an example of a non-contact force.
The force exerted by a charged body on another charged or uncharged body is known as electrostatic force.
Objects or things fall towards the earth because it pulls them. This force is called the force of gravity, or just gravity.
The force acting on a unit area of a surface is called pressure.
Pressure = Force/area on which it acts
Pressure Exerted by Liquids and Gases
The gases, too, exert pressure on the walls of their container.
The atmospheric air extends up to many kilometres above the surface of the earth. The pressure exerted by this air is known as atmospheric pressure.