 #1
PSN03
 100
 9
 Homework Statement:
 A source and an observer are situated on two perpendicular tracks as shown in the figure the observer is at rest and source is moving with a speed 50m/s the source emits sound waves of frequency 90Hz which travel in the medium with velocity 200m/s the frequency of sound heard by observer when the source crosses the origin is
 Relevant Equations:

By dopler's equation we know that
f'=f(v±vo/v±vs)
Where
f'= new frequency
vo=velocity of observer
vs=velocity of source
v=velocity of sound
My thought process was this,
They are asking us to find the frequency of sound received by observer when the source reaches at origin. According to me when the source reaches origin there would be no component of source's velocity in the direction of observer, hence vs=0
vo=0 since the observer is stationary
Therefore by the formula I should get the answer as
f'=f(v±0/v±0)
=f
Hence no change in frequency should be observed. But my answer is wrong.
Lease tell me where am I going wrong?
They are asking us to find the frequency of sound received by observer when the source reaches at origin. According to me when the source reaches origin there would be no component of source's velocity in the direction of observer, hence vs=0
vo=0 since the observer is stationary
Therefore by the formula I should get the answer as
f'=f(v±0/v±0)
=f
Hence no change in frequency should be observed. But my answer is wrong.
Lease tell me where am I going wrong?