Train on Bridge
The following problem was offered at the very first Moscow Mathematical Olympiad in 1935
It takes t1 seconds for a train to pass an observer and t2 seconds to clear a bridge of length L meters. Find the length and the speed of the train.
Note: t2 is the time between the train enters the bridge and the moment the last car gets off the bridge.
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Copyright © 1996-2018 Alexander Bogomolny
Solution
It takes t1 seconds for a train to pass an observer and t2 seconds to clear a bridge of length L meters. Find the length and the speed of the train.
Let V be the train's speed and S its length.
The first conditon of the problem tells us that
Subtracting the two gives L/V = t2 - t1, or
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Copyright © 1996-2018 Alexander Bogomolny
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