1. odcinek v=12km/h s=18km (s=v*t) t=1,5h 2. odcinek v=16km/h s=20km/h t = 1,25h (t=s/v) łączny czas - 1,25 + 1,5h = 1,75h łączny dystans - 18km+20km = 38km prędkość średnia to dx/dt, zatem 38km/1,75h = 22km/h (w przybliżeniu).
[latex]dane:\t_1 = 1,5 h\v_1 = 12frac{km}{h}\s_2 = 20 km\v_2 = 16frac{km}{h}\szukane:\v_{sr} = ?[/latex] [latex]v_{sr} = frac{s_{c}}{t_{c}}\\s_{c} = s_1 + s_2\s_1 = v_1 * t_1 = 12frac{km}{h}*1,5h = 18 km\s_2 = 20 km\s_{c} = 18km+20km = 38 km\\t_c} = t_{1} + t_2\t_1 = 1,5 h\t_2 = frac{s_2}{v_2} = frac{20km}{16frac{km}{h}} = 1,25 h\t_{c} = 1,5h + 1,25h = 2,75 h\\v_{sr} = frac{38km}{2,75h} = 13,818frac{km}{h}\\v_{sr}approx 13,82frac{km}{h}[/latex]
