Question

How come the priliminary contact forces ( friction and muscular force ) be precisely categorised into the 4 fundamental non - contact forces ?

Answer 1

I believe There is a Slight Misunderstanding in the Concept

Contact Force
Force that comes into action after the interaction between objects is called contact force. Contact force acts on the point of contact. For contact force; interaction between objects is necessary. Example; pushing a car, opening a drawer, kicking a ball, etc. In these examples, interaction between objects is necessary.
Muscular force, force of friction, etc. are types of contact force.
Muscular Force: -
Force caused by the action of muscles is called muscular force. In other words, force resulting because of action of muscle is called muscular force. Muscular force is applied only after interaction with the object. Hence it is a type of contact force.

Example : –
While kicking a ball, the player applies force over the ball using his leg muscles.
While opening a drawer, you pull the drawer holding it by hand. In this action, muscles of your hand apply the force.
While pulling a cart, the horse or the ox applies the force of its muscles.
Friction:
Force acting between the surfaces of two objects is called the force of friction. Force of friction always acts in the opposite direction of the movement of object. Force of friction is acting over all the moving objects.
Example -
A moving football stops after going to a certain distance. This happens because of force of friction between the surface of ground and the surface of football.

A moving boat stops after some distance because of friction between the surface of water and the surface of boat.
Since force of friction comes into action only after interaction between two objects, thus, it is a type of contact force.