Question

An ambulance is driving towards the hospital at a velocity 108 km/h and emitting a steady 798-Hz sound from its siren. The sound reflects off the front of the hospital and is received by the same ambulance. In addition to it's own siren, the ambulance hears a shifted tone from the reflection at what frequency? The speed of sound on this day is 343 m/s. a. 1.06e+3Hz b. 855Hz c. 850Hz d. 1.08e+3Hz e. 950 Hz

Answer 1

To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is a physical phenomenon where an apparent change in wave frequency is presented by a sound source with respect to its observer when that same source is in motion. Mathematically it can be described as

$f_d= f_s \frac{(v+v_d)}{(v-v_s)}$

The meaning of each of these variables is,

$v_d=$Velocity of detector

$f_s$=Frequency of wave emitted by source

$v_s=$Velocity of source

v=Velocity of sound wave

$f_d$=Frequency received by detector

Replacing we have that,

$f_d = 798(\frac{(343+30)}{(343-30)})$

$f_d=950 Hz$

Therefore the correct option is e. 950Hz