Wherever you are and whatever you are doing, even when you don’t realize it, force is always being applied by you and on you.
You are not only applying force when you are pushing a wall but also when you are simply standing.
A force is that physical cause which changes or tends to change the state of rest or state of uniform motion of a body. Its SI Unit is Newton (N), coined after the very famous Isaac Newton.
You don’t necessarily need to touch an object to be applying force on it. On this basis, forces are primarily divided into contact and non contact forces.
The forces which act on bodies when they are in direct contact are called contact forces.
Eg. Frictional force, normal reaction force, tension force etc.
The forces which act on bodies without being in contact with each other are called non contact forces. Eg. Gravitational force, magnetic force etc. The magnitude of force is inversely proportional to the distance of separation between the two bodies.
Subdivisions of Contact and Non Contact Forces-
Frictional Force: It is said that behind everything is science. When a ball is rolling on the ground, without having any other force applied on it, it stops rolling on its own.
Ever wonder why? It is nothing but this force. The force which opposes the relative motion between two surfaces in contact is called frictional force.
It is a type of contact force.
When the surface of the ball rubs with the surface of the ground, it slows the ball down, effectively stopping its motion completely after some time.
Normal Reaction Force: We are able to stand on the ground without falling. Even when we are simply standing, two forces are in play. Normal reaction force and gravitation force.
It is a kind of contact force. The Third Law of Newton states that, to every action there is an equal and opposite reaction.
Thus, when we stand, a force is applied by us on the ground in a downward direction and the ground applies equal force in the upward direction. This tends to equalize the force, thus helping us stand without tripping every second. In the same way, this force helps us to walk too.
Gravitational Force: When you throw a ball up, it always comes down. It comes down because of the force applied on it by the mass of earth. More the mass of the object, more will it apply force.
It is a non contact force. Every object applies gravitational force on every other object. Even a piece of paper applies gravitational force on us but is incapable in moving us because of its mass being less. Gravitational force is a force that attracts any object with mass. We, right now, are pulling on every object in this entire universe. This is called Newton’s Universal Law of Gravitation. Gravitational force is a vast topic, with tonnes of discovered and undiscovered knowledge about it.
Apart from this, there is magnetic force. Objects apply force on other objects having a charge opposite from that of itself. This is called magnetic force.
Force due to push and pull are forces that move or stop a body. It is applied in the opposite direction to the movement of the object.
The simplest form of force is mechanical force that we apply on a book to move it or basically on anything to move it.