2.8.3 (Unity3d): What is the exact calculation used for dynamic friction force?

I have the same problem. I’m using Unity 5.5 to calculate the rest distance of an object that has an initial velocity while sliding. I’m using these formulas given below;

Vfinal² = Vinitial² + 2ad
Vfinal² = Vinitial² + 2(F/m)d
0 = Vinitial² + 2((µmg)/m)d
0 = Vinitial² + 2µgd == > Vinitial² = -2µgd
Distance = Vinitial² / 2µg

With last equation i am calculating the rest distance but it is not accurate. If I increase the friction constant of the surface and the object to double in the formula I can predict the rest distance with nearly %95 accuracy. Am I missing something and How can I calculate the exact Friction Force?