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
625 Hz
n' = n(v−v0v+vs)=750(330−180×518330+180×518)=325Hz