On two parallel railway tracks, two trains are moving evenly towards each other: a freight train with a length of 630 m

On two parallel railway tracks, two trains are moving evenly towards each other: a freight train with a length of 630 m at a speed of 48 km / h and a passenger train with a length of 120 m at a speed of 102 km / h. How long does one train pass by the other?

Given:

L1 = 630 meters = 0.63 kilometers – the length of the freight train;

v1 = 48 km / h – the speed of the freight train;

L2 = 120 meters = 0.12 kilometers – the length of the passenger train;

v2 = 102 km / h – the speed of the passenger train.

It is required to determine the time t during which the trains pass each other.

Since the trains are moving towards each other, then we can assume that the passenger train is at rest, and the freight train is traveling towards it at a speed:

v = v1 + v2 = 48 + 102 = 150 km / h.

Then, the time will be equal to:

t = (L1 + L2) / v = (0.63 + 0.12) / 150 = 0.75 / 150 = 0.005 hours = 0.3 minutes = 18 seconds.

Answer: passages will pass each other in 18 seconds.