A train 110 metres long travels at 60 km/h. How many seconds does it take to completely cross a stationary telegraph post?

Difficulty: Easy

Correct Answer: 6.6 sec

Explanation:


Introduction / Context:
Crossing a point object (post/pole) requires the train to travel a distance equal to its own length at its running speed.


Given Data / Assumptions:

  • L = 110 m.
  • v = 60 km/h.


Concept / Approach:
Convert speed to m/s, then apply t = distance / speed = L / v.


Step-by-Step Solution:

v = 60 * 5/18 = 50/3 ≈ 16.6667 m/s.t = 110 / (50/3) = 110 * 3 / 50 = 6.6 s.


Verification / Alternative check:
Scale check: if length doubled to 220 m, time would double to 13.2 s at same speed, which is consistent.


Why Other Options Are Wrong:
5, 5.6, 6.8, 7.2 s are off from L/v after correct conversion.


Common Pitfalls:
Using km/h directly with metres; confusing platform/bridge case with post case.


Final Answer:
6.6 sec

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