[tex]dane:\\v_1 = 5\frac{m}{s} = 5\cdot3,6 \ \frac{km}{h} = 18\frac{km}{h}\\t_1 = \frac{1}{2} \ h\\v_2 = 72\frac{km}{h}\\t_2 = 10 \ min = \frac{1}{6} \ h\\szukane:\\v_{sr} = ?\\\\Rozwiazanie\\\\v_{sr} = \frac{s_{c}}{t_{c}}}[/tex]
[tex]s_{c} = s_1 + s_2\\s = v\cdot t\\s = v_1\cdot t_1 + v_2\cdot t_2 = 18\frac{km}{h}\cdot\frac{1}{2} \ h + 72\frac{km}{h} \cdot\frac{1}{6} \ h = (9 + 12) \ km = 21 \ km\\\\t_{c} = t_1 + t_2 = \frac{1}{2} \ h + \frac{1}{6} \ h = (\frac{3}{6}+\frac{1}{6}) \ h = \frac{4}{6} \ h = \frac{2}{3} \ h\\\\v_{sr} = \frac{21 \ km}{\frac{2}{3} \ h} = 21\cdot\frac{3}{2} \ \frac{km}{h}\\\\v_{sr} = 31,5\frac{km}{h}[/tex]
