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Two trains travel on parallel straight tracks in the same direction. The faster train moves at 30 m/s and overtakes the slower train, which moves at 20 m/s. Each train is 40 m long. How long does the overtaking manoeuvre take (from the moment the front of the faster train draws level with the rear of the slower train to the moment the rear of the faster train passes the front of the slower train)?
- 4 s
- 8 s
- 16 s
- 10 s
Correct answer: 8 s
Solution
In the frame of the slower train, the faster train must travel a total distance equal to the sum of both lengths (80 m) at a relative speed of 10 m/s, so the time elapsed is 80/10 = 8 s.
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