Question

Una ambulancia se desplaza hacia el norte. A 23, 5 m/s. Su sirena emite un sonido de 500 hz de frecuencia . Calcular la frecuencia aparente que percibe. Un observador. Que viaja en su auto, también hacia el norte. A 18, 6 m/s cuando : el auto se aleja de la ambulancia

Answer 1

The apparent frquency would be

f' = 493.26 Hz

Explanation:

This a Doppler's effect problem. This effects produces a slight change in the frequency of a traveling wave, due to the effect of the velocity of the receiver (observer).

The formula used to describe the change, as both vehicles are moving away of each other:

f' = [ (Vwave + Vobserver) / (Vwave + Vsource ) ]*f

Where

Vwave = 340 m/s ( speed of sound)

Vobserver = 18.6 m/s (observer = car)

Vsource = 23.5 m/s (speed of the ambulance = source)

f = 500 Hz (frequency of the sound)

We just need to substitute in the equation

f' = [(340+ 18.6) / (340+ 23.5)] * 500 Hz

f' = [0.9865] * 500 Hz = 493.26 Hz

f' = 493.26 Hz