Question

Two passenger trains moving with a speed of 108 km/hour cross each other. One of them blows a whistle whose frequency is 750 Hz. If sound speed is 330 m/s, then passengers sitting in the other train, after trains cross each other will hear sound whose frequency will be

• A. 900 Hz
• B. 625 Hz
• C. 750 Hz
• D. 800 Hz

Answer 1

Answer: (B)

625 Hz

Answer 2

$n' = n\left( \frac{v - v_{o}}{v + v_{s}} \right) = 750\left( \frac{330 - 180 \times \frac{5}{18}}{330 + 108 \times \frac{5}{18}} \right) = 625Hz$