Passengers in an auto traveling at 15.2 m/s toward the east hear a siren frequen
ID: 2290386 • Letter: P
Question
Passengers in an auto traveling at 15.2 m/s toward the east hear a siren frequency of 955 Hz from an emergency vehicle approaching them from behind at a speed (relative to the air and ground) of 43.7 m/s. The speed of sound in air is 340 m/s. (a) What siren frequency does a passenger riding in the emergency vehicle hear? (b) What frequency do the passengers in the auto hear after the emergency vehicle passes them?
!!!!!!!!!!!!!!!!!!!!!!!!!!!NOTE: THE ANSWER FOR a) IS NOT 955 OR 1046 HZ!!!!!!!!!!!!!!!!!!!!!!!!!1
Explanation / Answer
a)
955 = f*((340-15.2)/(340-43.7))
f = 955*(340-43.7)/(340-15.2)= 871.20 Hz
b)
f' = 871.2*((340+15.2)/(340+43.7)) = 806.49 Hz