An ambulance traveling eastbound at 144.0 km/h with sirens blaring at a frequenc

Question

An ambulance traveling eastbound at 144.0 km/h with sirens blaring at a frequency of 7.50 102 Hz passes cars traveling in both the eastbound and westbound directions at53.0 km/h. (Assume the speed of sound is 343 m/s.)

(a) What is the frequency observed by the eastbound drivers as the ambulance approaches from behind?
_______Hz

(b) What is the frequency observed by the eastbound drivers after the ambulance passes them?
_______Hz

(c) What is the frequency observed by the westbound drivers as the ambulance approaches them?
________ Hz

(d) What is the frequency observed by the westbound drivers after the ambulance passes them?
_________ Hz

Explanation / Answer

a)

VL = speed of listener = speed of eastbound drivers = 53 km/h = 53 (5/18) m/s = 14.72 m/s

Vs = speed of source = speed of eastbound ambulance = 144 km/h = 144 (5/18) = 40 m/s

frequncy observed by the eastbound drivers is given as

f' = (V - VL) f / (V - Vs)

f' = (343 - 14.72) (650) / (343 - 40) = 704.23 Hz

b)

VL = speed of listener = speed of eastbound drivers = 53 km/h = 53 (5/18) m/s = 14.72 m/s

Vs = speed of source = speed of eastbound ambulance = 144 km/h = 144 (5/18) = 40 m/s

frequncy observed by the eastbound drivers is given as

f' = (V - VL) f / (V + Vs)

f' = (343 + 14.72) (650) / (343 + 40) = 607.1 Hz

c)

VL = speed of listener = speed of eastbound drivers = 53 km/h = 53 (5/18) m/s = 14.72 m/s

Vs = speed of source = speed of eastbound ambulance = 144 km/h = 144 (5/18) = 40 m/s

frequncy observed by the eastbound drivers is given as

f' = (V + VL) f / (V - Vs)

f' = (343 + 14.72) (650) / (343 - 40) = 767.4 Hz

d)

VL = speed of listener = speed of eastbound drivers = 53 km/h = 53 (5/18) m/s = 14.72 m/s

Vs = speed of source = speed of eastbound ambulance = 144 km/h = 144 (5/18) = 40 m/s

frequncy observed by the eastbound drivers is given as

f' = (V - VL) f / (V + Vs)

f' = (343 - 14.72) (650) / (343 + 40) = 557.13 Hz

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