Variatia lungimii barei este
[tex]\displaystyle\Delta l(t)=k\Delta t[/tex]
,unde k este o constanta.
[tex]\displaystyle a)\Delta t_2=2\Delta t_1 \\ \\ \Delta l_1=k\Delta t_1 \\ \\ \Delta l_2=k\Delta t_2=2k\Delta t_1 \\ \\ \frac{\Delta l_1}{\Delta l_2}=\frac{k\Delta t_1}{2k\Delta t_1}=\frac{1}{2}\implies \Delta l_2=2\Delta l_1 \\ \\ b)\Delta l_3=2,5\Delta l_1 \\ \\ \Delta l_3=k\Delta t_3 \\ \\ 2,5\Delta l_1=k\Delta t_3 \\ \\ \frac{\Delta l_3}{\Delta l_1}=\frac{2,5\Delta l_1}{\Delta l_1}=\frac{k\Delta t_3}{k\Delta t_1} \\ \\ \frac{\Delta t_3}{\Delta t_1}=2,5[/tex]
