A passenger of a train traveling at a speed of 90 km / h sees for 8 seconds an oncoming

univerkov | April 2, 2021 | education

A passenger of a train traveling at a speed of 90 km / h sees for 8 seconds an oncoming freight train 320 m long. At what speed does a freight train move?

These tasks: V1 (speed of the train with this passenger) = 90 km / h (in SI V1 = 25 m / s); t (time of observation by a passenger of an oncoming freight train) = 8 s; L2 (length of freight train) = 320 m.

The speed of the oncoming freight train can be expressed from the formula: t = L2 / V1.2 = L2 / (V1 + V2), whence V1 + V2 = L2 / t and V2 = L2 / t – V1.

Let’s calculate: V2 = 320/8 – 25 = 40 – 25 = 15 m / s (54 km / h).

Answer: The oncoming freight train was supposed to have a speed of 54 km / h.

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