what is the formula for non-conservative forces

Question

experimentx · Answer

they have different formulas!!
for friction it's something like this 
$$ F = -\mu N$$

anonymous · Answer

OK, for an occasion when a object goes down a slope

anonymous · Answer

they say that change in KE and PE is the non-conservative

experimentx · Answer

KE and PE are not forces

anonymous · Answer

Ok, sorry for my wording but friction is involved in these energies

experimentx · Answer

well ...friction, air resistances is involved ...so??

anonymous · Answer

Ok, I get you point

experimentx · Answer

Frictional forces are involved ... that does not make gravitational force non conservative ... if you consider motion of particles without friction ... it will be independent of path ... only dependent on final and initial position!!

vincent-lyon.fr · Answer

$\vec\nabla \times \vec F\neq \vec 0$