A student in a parked car honks the horn, which has a `proper' frequency of 320 Hz. An observer in an approaching vehicle measures the frequency of the sound to be 355 Hz. Calculate the speed of the approaching vehicle. Use 340 m/s as the speed of sound in air.

Question

Henry · Answer

(V+Vr)/(V-Vs) * Fo = 355 Hz
(340+0)/(340-Vs) * 320 = 355
108800/(340-Vs) = 355
355(340-Vs) = 108800
340-Vs = 306.48
Vs = 340-306.48 = 33.5 m/s. = Velocity of source or vehicle.

Vr = Velocity of receiver or person.