The electric train is traveling at a speed of 20 m / s, a train is moving towards it on the next track at a speed of 36 km / h.

The electric train is traveling at a speed of 20 m / s, a train is moving towards it on the next track at a speed of 36 km / h. How long will the train pass by the passenger of the train if the train is 900 m long?

Given:

v1 = 20 m / s – train speed;

v2 = 36 km / h = 10 m / s – train speed;

L = 900 m – train length;

It is required to find t – the time that the train will pass by the passenger of the electric train.

Since the train and the electric train are moving towards each other, we can assume that the train is not moving, but the train is moving towards it with the speed v3 = v1 + v2

Then:

t = L / v3 = L / (v1 + v2) = 900 / (10 + 20) = 900/30 = 30 s.

Answer: the train will pass by the passenger of the train for 30 seconds.