Vezi imaginea atasata in care sunt explicate fortele:
[tex]\displaystyle\bf\\ m=3Kg\\\mu=0,4\\g\approx10\\G=mg=3\times10=30~N\\G_N=G\,cos~30^o=30\times\frac{\sqrt{3}}{2}=15\sqrt{3}~N\\ G_T=G\,sin~30^0=30\times\frac{1}{2}=15N\\ N=G_N=15\sqrt{3}~N\\Ff=\mu N=0,4\times 15\sqrt{3}=6\sqrt{3}\approx10,\!38~N\\Ft=G_T+Ff=15+10,\!38\approx25,38\,N\\\\Fc=\frac{Ft}{cos\,45^o}=\frac{~~Ft~~}{\dfrac{\sqrt{2}}{2}}=\frac{2\times Ft}{\sqrt{2}}=1,41\times 25,38\approx~\boxed{\bf35,79~N}\\\\ \boxed{\textbf{Copilul trage cu forta }~\bf~~Fc\approx35,79~N}[/tex]
