Even though the pressure increases when the area of contact decreases why doesn't friction increase with decrease in area?

  • $\begingroup$ Welcome to Physics! I've reverted an edit where you asked a separate interesting question; I thought the second one was different enough to stand on its own. $\endgroup$ – rob May 23 '20 at 5:54
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    $\begingroup$ Does this answer your question? Dependence of Friction on Area $\endgroup$ – SarGe May 23 '20 at 6:13

Friction is directly proportional to the normal force acting on the body, i.e.;

$$f \propto N$$ where $f =$ friction force and $N =$ Normal force

$$\boxed {f = \mu N}$$

where $\mu$ is the coefficient of friction and depends upon the surface.

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We can also say that the normal force does not depend upon the area of contact and hence the friction.

Pressure, on the other hand is:

$$\boxed{P = \frac{F}{A}}$$

where $F$ is the force acting and $A$ is the Area of contact. Thus pressure depends upon the area of contact.


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