[tex]\displaystyle\bf\\\\l_0=20m,~F=100N,~\Delta l=0,5mm=0,0005m,~E=1,96\cdot10^{11}N/m^2.[/tex]
[tex]\displaystyle\bf\\trebuie~sa~aflam~sectiunea~transversala~a~barei,~pentru~asta~vom~folosi~:\\k=\frac{E\cdot S}{l_0} =\frac{F_e}{\Delta l},~\implies E\cdot S\cdot\Delta l= F_e\cdot l_0 \implies S = \frac{F_e\cdot l_0}{E\cdot \Delta l}.[/tex]
