A train moving with speed 72 km h−1 emits a whistle of frequency 600 Hz. A

Question

person is standing stationary on the platform. Calculate the frequency heard by the
person if the train (i) approaches and (ii) recedes away from the listener.

Answer 1

Vt = 72,000m/h = 72,000m/3600s = 20 m/s.

1. Fp = (Vs+Vp)/(Vs-Vt) * Ft.
Fp = (343+0)/(343-20) * 600 = 637 Hz.

2. Fp = (343+0)/(343+20) * 600 = 567 Hz.