How long will a passenger sitting at the window of a train traveling at a speed of 54 km / h

| July 17, 2021 | education

How long will a passenger sitting at the window of a train traveling at a speed of 54 km / h see an oncoming train passing by him at a speed of 72 km / h? Train length 150 m

V1 = 54 km / h = 15 m / s.
V2 = 72 km / h = 20 m / s.
S = 150 m.
t -?
Since the trains go towards each other, the speed of the passing train V relative to the passenger will be the sum of the speeds of the two trains: V = V1 + V2.
The passenger will start watching the oncoming train when his first car is on the same level with him. He will finish watching him when the last car of the oncoming train passes.
A train of length S = 150 m will travel along the passenger at a speed V = V1 + V2.
The train travel time will be: t = S / (V1 + V2).
t = 150 m / (15 m / s + 20 m / s) = 4.28 s.
Answer: the passenger will observe the oncoming train for a time t = 4.28 s.



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