[tex]dane:\\s_1 = 20 \ km\\t_1 = 15 \ min\\s_2 = 30 \ km\\t_2 = 20 \ min\\szukane:\\v_{sr} = ?\\\\Rozwiazanie\\\\v_{sr} = \frac{s_{c}}{t_{c}}\\\\s_{c} = s_1 + s_2 = (20+30) \ km = 50 \ km\\\\t_{c} =t_1 + t_2 = (15+20) \ min = 35 \ min = \frac{35}{60} \ h = \frac{7}{12} \ h\\\\v_{sr} = \frac{50 \ km}{\frac{7}{12}h} = 50\cdot\frac{12}{7} \ \frac{km}{h} \approx 85,7\frac{km}{h}[/tex]
Odp. Średnia szybkość tego ciała wynosi ok. 85,7 km/h.
