[tex]Dane:\\v_{o} = 0\\t = 5 \ s\\v = 70\frac{km}{h} = 70\cdot\frac{1000 \ m}{3600 \ s} \approx19,44\frac{m}{s}\\Szukane:\\a = ?\\\\Rozwiazanie\\\\a = \frac{\Delta v}{t} = \frac{v-v_{o}}{t} = \frac{v}{t}\\\\a \approx \frac{19,44\frac{m}{s}}{5 \ s}\\\\\boxed{a \approx3,9\frac{m}{s^{2}}}[/tex]
