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Q138 (IAS/1998) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Quantitative aptitude topics Answer Verified

One local and another express train were proceeding in the same direction on parallel tracks at 29 km/hour and 65 km/hour respectively. The driver of the former noticed that it took exactly 16 seconds for the faster train to pass by him. What is the length of the faster train?

Result
Your answer: —  Â·  Correct: C
Explanation

When two trains move in the same direction, their relative speed equals the difference of their speeds; here 65 − 29 = 36 km/h (concept of relative motion). Convert 36 km/h to m/s by multiplying by 1000/3600 (or 5/18), giving 36 × (5/18) = 10 m/s (unit conversion method) [1]. The distance the faster train covers relative to the driver in 16 s is distance = relative speed × time = 10 m/s × 16 s = 160 m. Hence the length of the faster train is 160 metres, corresponding to option 3.

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > Speed = Total distance covered Total time taken > p. 114
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