OpenStudy (kainui):

Since coefficient of friction has no units, but friction depends on the normal force, what exactly is happening at the molecular level between the surfaces? I'm not sure I know how someone might geometrically calculate friction similar to how you might calculate the ideal gas law.

OpenStudy (isaiah.feynman):

Friction deeply is a quantum mechanical phenomenon.

OpenStudy (kainui):

Alright what operator do I use on what wave function to calculate the coefficient of friction?

OpenStudy (isaiah.feynman):

I dunno that. Sorry.

OpenStudy (isaiah.feynman):

Oh coefficient of friction can only be determined experimentally.

OpenStudy (isaiah.feynman):

(My physics textbook)

OpenStudy (turingtest):

I think a geometrical calculation would be hard, since the form of each molecule is intricate and you would have to take into account coulombic forces, but I have heard the rough analogy of rubbing serrated edges together|dw:1387860821957:dw|this gives an idea of why the coefficient of static friction is higher than kinetic, since once these surfaces start moving across one another the forms don't fully lock together, and they sort of glide across the peaks. This is, of course, a very rough analogy for what is, in all likelihood, a poorly understood quantum phenomenon.

OpenStudy (kainui):

Well to be honest this is exactly the kind of thing I'm always looking for. Just like the ideal gas law is only an approximation, I think an ideal friction law might be interesting to try to figure out based on density and electronegativities, etc... Thanks.

OpenStudy (turingtest):

I assume you already know that the coefficient of static friction is determined experimentally as the tangent of the critical angle. If you know of another method to calculate it, I'd sure like to know :)