[tex] a) F _{f} = \frac{1}{10} * G = \frac{1}{10} * (m*g)
= \frac{1}{10} * (20*10) = \frac{1}{10} *200=20Newton \\ b) F_{f} = coeficientul de frecare * N \\ v=ct => a=0 => R=0 => F_{f}=F tractiune; G=N
\\ Coeficientul de frecare = \frac{F}{G} = \frac{1}{10} =0,1
[/tex]