1.
[tex]Dane:\\v_{o} = 270\frac{km}{h}\\t = 21 \ s\\v = 385\frac{km}{h}\\Szukane:\\a = ?\\\\a = \frac{\Delta v}{t}\\\\\Delta v = v-v_o = (385-270) \ \frac{km}{h} = 115\frac{km}{h} = 115\cdot\frac{1000 \ m}{3600 \ s} = 31,9(4)\frac{m}{s} \approx 31,94\frac{m}{s}\\\\a \approx \frac{31,94\frac{m}{s}}{21 \ s}\\\\\boxed{a \approx1,52\frac{m}{s^{2}}}[/tex]
2.
[tex]Dane:\\v_{o} = 0\\t = 20 \ s\\s = 700 \ m\\Szukane:\\v = ?\\\\s = v_{sr}\cdot t\\\\v_{sr} = \frac{v-v_{o}}{t} = \frac{1}{2}v\\\\s = \frac{1}{2}vt \ \ /\cdot 2\\\\vt = 2s \ \ /:t\\\\v = \frac{2s}{t}\\\\v = \frac{2\cdot700 \ m}{20 \ s}\\\\\boxed{v = 70\frac{m}{s}=252\frac{km}{h}}[/tex]
