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

Answer 1

a)

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

V_s = 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 - V_L) f / (V - V_s)

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

b)

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

V_s = 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 - V_L) f / (V + V_s)

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

c)

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

V_s = 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 + V_L) f / (V - V_s)

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

d)

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

V_s = 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 - V_L) f / (V + V_s)

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