[tex]k=98 \ N/m \\ m=2 \ kg \\ g=10 \ N/kg \\ \boxed{L-?} \\ \bold{Rezolvare:} \\ \boxed{L=F \cdot d} \\ \boxed{k= \frac{F}{\triangle l}} \\ d=\triangle l \\ F=G=m \cdot g \\ F=G=2 \ kg \cdot 10 \ N/kg \\ F=20 \ N \\ \Rightarrow \triangle l= \frac{20 \ N}{98 \ N/m} \\ \triangle l=d= 0,204 \ m \\ L=20\ N \cdot 0,204 \ m \\ \Rightarrow \boxed{L=4.081 \ J}[/tex]
