Multiple choice

A 175-m long train is travelling along a straight track with a velocity of 72 km/h. A bird is flying parallel to the train in the opposite direction with a velocity of 18 km/h. The time taken by the bird to cross the train is

  1. 35 seconds

  2. 27 seconds

  3. 11.6 seconds

  4. 7 seconds
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D Correct answer
Explanation

Relative speed = 72 + 18 = 90 km/h = 90 * (5/18) = 25 m/s. Time = Distance / Speed = 175 / 25 = 7 seconds.

AI explanation

Using the relative speed formula for opposite directions, add the speeds to get 72 km/h plus 18 km/h, totaling 90 km/h. Convert this to meters per second by multiplying by 5/18, resulting in 25 m/s. The time for the bird to cross the train is the train length divided by the relative speed, so 175 divided by 25 equals 7 seconds.

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