When any object is placed on a surface, it exerts a strength about the object contrary to the Weight for that object to remain in balance. This force is called normal strength (FN) and it has the same direction of action as the weight, but its direction is opposite.
Why is this force called Normal?
The normal force is always perpendicular to the surface on which the body is deposited. In Geometry, the word normal is a synonym for perpendicular.
Is Normal a Weight Force Reaction?
It is common to hear that the normal force is a reaction of the weight force, in reference to the Newton's third law (action and reaction); still, normal force does not form a pair of action and reaction with weight force.
Normal strength and weight act on the same body
The third law of Newton says the action and reaction are forces applied to different bodies. Imagine a person slapping a wall. Action is about the wall, and reaction is about the individual's hand. In the case of the normal force, the weight is the result of the gravitational attraction suffered by the object in relation to the Earth, and the normal is a force made by the surface also on the object. Since the two forces (weight and normal) act on the same body, they cannot form an action and reaction pair.
By Joab Silas
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/fisica/o-que-e-forca-normal.htm
