s1 = 20 km v1 = 36 km/h s2 = 40 km v2 = 40 m/s = 144 km/h [latex]v_{sr} = frac{s_c}{t_c}\[/latex] tc = t1 + t2 t1 = s1/v1 t2 = s2/v2 [latex]v_{sr} = frac{s_1 + s_2}{t_1 + t_2}\ v_{sr} = frac{s_1 + s_2 }{frac{s_1}{v_1} + frac{s_2}{v_2}}\ v_{sr} = frac{20 km + 40 km}{frac{20}{36} + frac{40}{144}} = frac{60 km}{frac{80}{144} + frac{40}{144}} = frac{60 km}{frac{120}{144}} = 72 frac{km}{h} [/latex]
dane: s1 = 20 km v1 = 36 km/h s2 = 40 km v2 = 40 m/s = 40 x 0,001km /1/3600h = 144 km/h szukane: vśr = ? vśr = s/t s = s1+ s2 = 20km + 40 km = 60 km t = t1 + t2 t = s/v t1 = s1/v1 = 20km /36km/h = 5/9 h t2 = s2/v2 = 40km /144km/h = 5/18 h t = 5/9 h + 5/18 h = (10/18 + 5/18)h = 15/18 h = 5/6 h vśr = 60km : 5/6h vśr = 72 km/h ============= Odp.Szukana prędkość średnia pojazdu to 72 km/h.
