Vср = Sобщий / tобщее = (S1 + S2) / (S1:V1 + S2:V2)
S1/V1 + S2/V2 = (S1 + S2) / Vср
S2/V2 = (S1 + S2) / (Vср) - S1/V1
V2 = S2 / ((S1 + S2) / (Vср) - S1/V1) = S2 / ((V1*S - Vcр*S1) / (Vcp*V1)) = (3/4)*S / ((V1*S - Vcp*(1/4)*S) / (Vcp*V1)) = (3/4)*S*Vcp*V1 / (S*(V1 - (1/4)*Vcp)) = (3/4)*Vcp*V1 / (V1 - (1/4)*Vcp)
V2 = (3/4)*40*60 / (60 - (1/4)*40) = (3/4)*2400 / (60 - 10) = 1800 / 50 = 36 км/ч
36 км/ч = 36000 / 3600 = 10 м/с.
Vср = Sобщий / tобщее = (S1 + S2) / (S1:V1 + S2:V2)
S1/V1 + S2/V2 = (S1 + S2) / Vср
S2/V2 = (S1 + S2) / (Vср) - S1/V1
V2 = S2 / ((S1 + S2) / (Vср) - S1/V1) = S2 / ((V1*S - Vcр*S1) / (Vcp*V1)) = (3/4)*S / ((V1*S - Vcp*(1/4)*S) / (Vcp*V1)) = (3/4)*S*Vcp*V1 / (S*(V1 - (1/4)*Vcp)) = (3/4)*Vcp*V1 / (V1 - (1/4)*Vcp)
V2 = (3/4)*40*60 / (60 - (1/4)*40) = (3/4)*2400 / (60 - 10) = 1800 / 50 = 36 км/ч
36 км/ч = 36000 / 3600 = 10 м/с.