posted by aok .
A stationary horn emits a 135-Hz tone. What frequency is heard by a passenger on a train which is moving towards this horn with a speed of 31.3 m/s?
F = ((V + Vr) / V) * Fo. V IN m/s.
F = ((343 + 31.3) / 343) * 135 Hz,
F = (374.3 / 343) * 135 = 147.3 Hz.