I learned that friction comes from the tiny crashes between the small bumps of uneven surface of each object. And I could make a rough guess about why heat is produced when two objects are rubbed together. Since friction is made by bumps(?) on the surface, the force you push downward(vertical to the surface),and the friction seems like it does not have to satisfy the linear equation such as

$$F= μN$$

For conclusion, is the explanation of friction using the bumps right? And if it is, in what specific structure of the surface can they satisfy a tendency of linear equation even though the linear equation is just a simple mathematical concept?

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    $\begingroup$ Possible duplicate of Why is the equation for friction so simple? $\endgroup$ – BioPhysicist Sep 20 '18 at 17:51
  • $\begingroup$ Thanks for the article. But I wanted to know about how actually friction is made and the possible structure of a surface to create a linear equation satisfying force. $\endgroup$ – Charles Kim Sep 20 '18 at 18:10
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    $\begingroup$ It doesn't (most likely) take the actual form of a linear equation. It is a simple linear model that for sure does not work in certain situations. However, it still does work for many other situations. This is why it is used. It is useful and accurate enough to describe friction between many different types of materials. There isn't a single description of friction. The actual mechanisms at play greatly depend on what surfaces you are looking at. $\endgroup$ – BioPhysicist Sep 20 '18 at 18:14
  • $\begingroup$ Almost every resistances are approximated with some kinds of taylor expansions. $\endgroup$ – KYHSGeekCode Sep 28 '18 at 8:24