((16.46)Q:9) A railroad train is traveling at a speed of 25.5 m/s in still air.
ID: 1482105 • Letter: #
Question
((16.46)Q:9)
A railroad train is traveling at a speed of 25.5 m/s in still air. The frequency of the note emitted by the locomotive whistle is 440 Hz
A)
What is the wavelength of the sound waves in front of the locomotive?
Use 344 m/s for the speed of sound in air
B)
What is the wavelength of the sound waves behind the locomotive?
Use 344 m/s for the speed of sound in air.
C)
What is the frequency of the sound heard by a stationary listener in front of the locomotive?
Use 344 m/s for the speed of sound in air.
D)
What is the frequency of the sound heard by a stationary listener behind the locomotive?
Use 344 m/s for the speed of sound in air.
Explanation / Answer
given sound velocity is v = 344 m / s
a)
wavelength = v / f
= ( 344 - 25.5 ) / 440
= 0.7238m
b)
similarly = v / f
= ( 344 + 25.5 ) / 440
=0.8397 m
c)
fd = f ( v + vr ) / ( v - vs )
where f =440 Hz ,
v = 344 m / s ,
vr = 0 ,
vs = 25.5 m / s
fd = 440 ( 344 + 0 ) / ( 344 - 25.5 )
= 151360 / 318.5
fd = 475.227 Hz
d)
fd = f ( v + vr ) / ( v + vs )
where f =440 Hz ,
v = 344 m / s ,
vr = 0 ,
vs = 25.5 m / s
fd = 440 ( 344 + 0 ) / ( 344 + 25.5 )
= 151360 / 369.5
fd = 409.634 Hz
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