Odpowiedź:
Vśr - prędkość średnia
V - prędkość
t - czas
tc - cały czas
s - droga
sc - cała droga
[tex]V_{sr} = \frac{s_{c} }{t_{c} }[/tex]
[tex]s_{c} = s_{1}+ s_{2}[/tex]
[tex]s_{1}[/tex] = 6 km = 6000 m
[tex]s_{2}[/tex] = 18 km = 18000 m
[tex]s_{c}[/tex] = 6000 + 18000 = 24000m
[tex]t_{c} = t_{1}+ t_{2}[/tex]
[tex]t = \frac{s}{v}[/tex]
[tex]t_{1} = \frac{s_{1} }{v_{1} }[/tex] = 6/12 = 1/2h = 1800 sek
[tex]t_{2} =\frac{s_{2} }{v_{2} }[/tex] = 3/18 = 1/6h = 600 sek
[tex]t_{c} = 1800 + 600= 2400[/tex] sek
[tex]v_{sr} = \frac{24000}{2400} = \frac{240}{24} = \frac{10}{1} = 10[/tex] [tex]\frac{m}{s}[/tex]
