Multiple choice

A train has crossed a man in 7 seconds who is running on the platform with a speed of 5 km/hour in the opposite direction of the train. if the speed of the train is 31 km/hour then find the length of the train.

  1. 70 m

  2. 60 m

  3. 80 m

  4. 90 m
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A Correct answer
Explanation

The relative speed of the train with respect to the man running in opposite direction is 31 + 5 = 36 km/hr = 10 m/s. Since the train crosses the man in 7 seconds, the length of the train = relative speed × time = 10 × 7 = 70 m. When objects move in opposite directions, their speeds are added.

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