desen 1: plan inclinat, asupra corpului actioneaza fortele :
G (vector) + N(vector) + Ff(vector) + Fn(vector) = 0
in lungul planului : Gx - Ff = 0 Gsinα - μN = 0
perpendicular pe plan : Gy + Fn = N Gcosα + Fn = N
Gsinα -μ(Gcosα +Fn) = 0 Fn = G(sinα - μcosα) /μ
desen 2 : plan inclinat, corp, forte (G, N,Ff,Fo)
G(vector) + N(vector) + Ff(vector) + Fo(vector) = 0
paralel cu planul : Gx = μN + Focosα
_|_ pe plan : N = Gy + Fosinα Gsinα = μ(Gcosα+Fosinα) +Focosα
Fo = G(sinα- μcosα)/(μsinα+cosα)
Fn = nFo
G(sinα - μcosα) /μ = nG(sinα - μcosα)/(μsinα + cosα)
1/μ = n/(μsinα + cosα) μsinα + cosα = μn μ = cosα / (n - sinα)