Pole crossing at 72 km/h – find length A train moving at 72 km/h crosses a pole in 15 s. What is its length?

Difficulty: Easy

Correct Answer: 300 m

Explanation:

Introduction / Context:The pole is a point obstacle; the entire train passes by, so distance equals the train length. Apply unit conversion and multiply speed by time to get the length.

Given Data / Assumptions:

  • v = 72 km/h = 20 m/s.
  • t = 15 s.

Concept / Approach:L = v * t after converting to m/s.

Step-by-Step Solution:

L = 20 * 15 = 300 m

Verification / Alternative check:Reverse: 300 m / 20 m/s = 15 s, consistent.

Why Other Options Are Wrong:150 m, 200 m, 350 m: Each contradicts the exact multiplication result.

Common Pitfalls:Leaving units as km/h and seconds without conversion leads to wrong answers.

Final Answer:300 m

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