Two train whistles, A and B, each have a frequency of 392 Hz. A is stationary and B is moving toward the right?

Question

—(away from A) at a speed of 35.0m/s. A listener is between the two whistles and is moving toward the right with a speed of 15.0m/s. No wind is blowing. a) What is the frequency from A as heard by the listener? b) What is the frequency from B as heard by the listener? c) What is the beat frequency detected by the listener?note:(there are no question mark”?” in the right (away from A) is the continuations ty…)

Bernhard White · Accepted Answer

this is doppler effect.observed frequency=f=((v+vl)/(v+vs))*fov=velocity of wave in medium=343m/s vl=velocity of listener(+ if listener moving towards the source and – if moving away from source)vs=velocity of source(+if source moving away from observer and – if source moving towards observer)a)v=343,vl= -15vs=0f0=392fa can be found.b)v=343vl=15vs=35f0=392fb can be found.c)beat frequency=fa-fb

Bernhard White · Answer

with respect to A the listener is opening the distance at 15 m/sF = Fo ( V / ( V + Vl )where V is speed of sound and Vl is relative speed of listenerF = 392 ( 343 / (343+15) = 375.6with respect to B the source is moving away from the listener at 20 m/sF = Fo ( ( V – Vs ) / Vwhere Vs is the speed of the sourceF = 392 ( (343-20) / 343 ) = 369.1 the difference gives 6.5 beats/sec

Bernhard White · Answer

B

Jonathon Rolfson

Two train whistles, A and B, each have a frequency of 392 Hz. A is stationary and B is moving toward the right?

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