Q. 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) $800\ Hz$
Explanation
(b) $n^{'} = n\left( \frac{v - v_{O}}{v - v_{S}} \right) = 750\left( \frac{330 - 180 \times \frac{5}{18}}{330 + 108 \times \frac{5}{18}} \right) = 625Hz$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.