Distance between points A and B 100 km The car drove from point A to point B at a speed of 40 km / h

| January 15, 2021 | education

Distance between points A and B 100 km The car drove from point A to point B at a speed of 40 km / h and stopped at point B for 15 minutes. and continued to move to point C at a speed of 14 m / s. B point C the car arrived in 4 hours from the start of movement from point A. Determine the average speed for the entire journey.

Sav = 100 km = 100000 m.
Vav = 40 km / h = 11.1 m / s.
tv = 15 min = 900 s.
Vs = 14 m / s.
tac = 4 h = 14400 s.
Vav -?
To find the average vehicle speed Vav, it is necessary to divide the entire path of movement from point A to C Sac by the time of movement tac: Vav = Sac / tac.
The entire path Sac will be the sum: Sac = Saw + Svs.
Let’s find the distance between points B and C according to the formula: Svs = Vs * ts, where Vs is the speed of movement from B to C, tvs is the time of movement from B to C.
tвс = tс – tв – tв.
tav = Sav / Vav.
tav = 100000 m / 11.1 m / s = 9009 s.
tvs = 14400 s – 900 s – 9009 s = 4491 s.
Sws = 14 m / s * 4491 s = 62874 m.
Sac = 100000 m + 62874 m = 162874 m.
Vav = 162874 m / 14400 s = 11.31 m / s.
Answer: the average vehicle speed is Vav = 11.31 m / s.



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