A railroad train is traveling at 31.0 m/s in still air. The frequency of the not
ID: 1618037 • Letter: A
Question
A railroad train is traveling at 31.0 m/s in still air. The frequency of the note emitted by the locomotive whistle is 500 Hz. (Assume the speed of sound in air is 344 m/s.) (a) What is the wavelength of the sound waves in front of the locomotive? m (b) What is the wavelength of the sound waves behind the locomotive? m (c) What is the frequency of the sound heard by a stationary listener in front of the locomotive? Hz (d) What is the frequency of the sound heard by a stationary listener behind the locomotive? HzExplanation / Answer
let,
object speed, vo=31 /sec
frequency of the source, fs=500 Hz
velocity of the sound, vs=344m/sec
a)
frquency in front of the train,
fo=fs*(vs/(vs-vo))
fo=500*(344/(344-31))
fo=549.52 Hz
and
wavelength, lambda=vs/fo
=344/(549.52)
=0.626 m
b)
frquency behind the train,
fo=fs*(vs/(vs+vo))
fo=500*(344/(344+31))
fo=458.66 Hz
and
wavelength, lambda=vs/fo
=344/(458.66)
=0.75 m
c)
fo=549.52 Hz
d)
fo=458.66 Hz
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