[tex]dane:\\v_1 = 90\frac{km}{h}\\t_1 = 4 \ h\\v_2 = 80\frac{km}{h}\\t_2 = 3 \ h\\szukane:\\v_{sr} = ?\\\\Rozwiazanie\\\\v_{sr} = \frac{s_{c}}{t_{c}}\\\\s = v\cdot t\\\\s_1 = v_1\cdot t_1 = 90\frac{km}{h}\cdot4 \ h = 360 \ km\\\\s_2 = v_2\cdot t_2 = 80\frac{km}{h}\cdot3 \ h = 240 \ km\\\\s_{c} = s_1 + s_2 = 360 \ km + 240 \ lm = 600 \ km\\\\t_{c} = t_1 + t_2 = 4 \ h + 3 \ h = 7 \ h\\\\v_{sr} = \frac{600 \ km}{7 \ h} \approx85,71\frac{km}{h}[/tex]
Odp. Prędkość średnia pociągu na całej trasie wynosi ok.85,71 km/h.
