[tex]m_1=2 \ kg \\ \triangle l_1=4 \ cm=0,04 \ m \\ m_2=2,5 \ kg \\ \boxed{\triangle l_2 - ?} \\ \bold{Rezolvare:} \\ \boxed{k= \frac{F_e}{\triangle l} } \\ \Rightarrow \triangle l_2= \frac{F_e_2}{k} \\ k= \frac{F_e_1}{\triangle l_1} \\ F_e=G=m \cdot g \\ \Rightarrow F_e_1=G_1=m_1 \cdot g \\ F_e_1=2 \kg \cdot 10 \ N/kg=20 \ N \\ k= \frac{20 \ N}{0,04 \ m} =500 \ N/m \\ \Rightarrow \triangle l_2= \frac{m_2 \cdot g}{k} = \frac{2,5 \ kg \cdot 10 \ N/kg}{500 \ N/m} = \frac{25 \ N}{500 \ N/m} [/tex]
[tex] \Rightarrow \boxed{\triangle l_2=0,05 \ m}.[/tex]
