r (randamentul)=[tex] \frac{L u_ }{L c_ } [/tex]
r=[tex] \frac{R*d R_ }{F*dF} = \frac{R*bR}{F*bF} =\ \textgreater \ r*F*bF=R*bR
F= \frac{R*bR}{r*bF} = \frac{40N* \frac{2}{5} *bF}{0,8*bF} = \frac{ \frac{80}{5} N}{0,8} [/tex][tex]F= \frac{16N}{0,8} =20N[/tex]