Question

How long will a passenger sitting at the window of a train travelling at a speed of 54 km$h^{-1}$ see a train,passing by in the opposite direction with a speed of 36 km$h^{-1}$ , if the length of the second train is 150 m?

• A. 10 s
• B. 6 s
• C. 6 min
• D. 8 min

Answer 1

Answer: (B)

6 s

Answer 2

Relative speed of 1st train w.r.t. IInd $= (54 + 36) kmh^{-1} = 90 \times \frac{5}{18} ms^{-1}$ $= 25 \, ms^{-1}$ Time duration to pass IInd train $= \frac{150}{25} = 6 \, s$