v₁=60 km/h
v₂=40 km/h
S₁=S₂= 0,5 S
vsr = ?
[tex]v_{\'sr}=\frac{S_{calkowita}}{t_{calkowity}}[/tex]
Sc=S₁+S₂
tc=t₁+t₂
[tex]v=\frac{S}{t} \ \ \rightarrow \ \ t=\frac{S}{v}[/tex]
[tex]v_{\'sr}=\frac{S_1+S_2}{t_1+t_2}=\frac{0,5 \ S+0,5 \ S}{\frac{S_1}{v_1}+\frac{S_2}{v_2}}=\frac{S}{\frac{S_1v_2+S_2v_1}{v_1v_1}}=\frac{S}{\frac{0,5 \ S \ (v_1+v_2)}{v_1v_2}}=S*\frac{v_1v_2}{0,5 \ S \ (v_1+v_2)}=\\ \\ \\v_{\'sr}=\frac{2v_1v_2}{v_1+v_2}=\frac{2*60 \ [\frac{km}{h}]*40 \ [\frac{km}{h}]}{60 \ [\frac{km}{h}]+40 \ [\frac{km}{h}]}=\frac{4800 \ [\frac{km^2}{h^2}]}{100 \ [\frac{km}{h}]}=48 \ \frac{km}{h}[/tex]
