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

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SUMMARY

The discussion clarifies that surface area does not directly influence the normal force in frictional interactions. The normal force arises from electromagnetic interactions between the body and the surface, remaining constant regardless of surface area. The frictional force is expressed as F(fric) = μ × N, where μ is the friction coefficient and N is the normal force. The analysis introduces the concept of force density, indicating that while pressure density changes with surface area, these changes cancel out, resulting in a consistent frictional force.

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  • Knowledge of electromagnetic interactions and their role in normal force.
  • Concept of pressure density and its application in force calculations.
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starablaze
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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?
 
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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.
 

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