Why does surface area not directly affect normal force in friction?

[starablaze]

could you tell me why the surface area does not affect the surface area? isn't the normal force due to the electromagnetic interactions between the body and the surface? so the greater the surface area, the greater the normal force,right?

so the frictional force will depend on surface area,in the expression

friction=mu x normal force

no?

 

[jomoonrain]

In fact, I think we can define a force (areal) density f here.
And the frictional force is:
F(fric)=Nu=[f1 x A(area)]u=f2 x A, N is the pressure (the body give to the suface),u is friction coefficient,f1 is the pressure density, f2 is the frictional force density
for a given body, the pressure N is fixed, and the change of the area can only affect the pressure density and so the frictional force density.

So,although the area is changed, the force density is also changed, and fortunately they happen to cancel out.

 

[astrokreng]

I can provide some clarification on the relationship between surface area, normal force, and frictional force. First, it is important to understand that frictional force is caused by the resistance between two surfaces in contact. This resistance is due to the irregularities and imperfections on the surfaces, which create small bumps and valleys that interlock and resist movement.

The normal force, on the other hand, is the force exerted by one surface on another in a direction perpendicular to the surface. This force is indeed caused by electromagnetic interactions between the body and the surface, as you mentioned.

Now, the important thing to note is that the normal force is not directly affected by the surface area. The normal force is dependent on the weight or mass of the object and the gravitational pull, not the surface area. This means that even if you increase the surface area of the object, the normal force will remain the same as long as the weight and gravitational pull do not change.

On the other hand, the frictional force is indeed affected by the surface area, as shown in the expression you provided. The coefficient of friction (mu) is a measure of the roughness of the surfaces in contact and will remain constant. However, the normal force, which is a component of the frictional force, will increase as the surface area increases, resulting in a higher frictional force.

In summary, the surface area does not directly affect the normal force, but it does indirectly affect the frictional force through its influence on the normal force. I hope this explanation helps to clarify any confusion.