A truck passed the gas station at a speed of 54 km / h. Two hours later, in the opposite direction, a passenger

| May 5, 2021 | education

A truck passed the gas station at a speed of 54 km / h. Two hours later, in the opposite direction, a passenger car with a speed of 72 km / h passed by the same gas station. How far from the gas station did they meet?

Vg = 54 km / h = 15 m / s.

Vl = 20 m / s.

t = 2 h = 7200 s.

Sl -?

When a passenger car passed the gas station, the truck was already at a distance from it S1 = Vg * t.

Before the meeting, a passenger car will travel the distance Sl = Vl * tvs, a truck will travel the distance Sg = Vg * tvs.

Moreover, Sl = S1 + Sg, Vl * tvs = Vg * t + Vg * tvs.

tvs = Vg * t / (Vl – Vg).

tvs = 15 m / s * 7200 s / (20 m / s – 15 m / s) = 21600 s.

Sl = 20 m / s * 21600 s = 432000 m = 432 km.

Answer: a passenger car will catch up with a truck at a distance of Sl = 432 km from the gas station.



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