Ek physics 750

[yingao88]

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The source of a sound wave is stationary. The observer is moving toward the source. There is a steady wind blowing from observer to the source. How does the wind change the observed frequency?

A. Wind magnifies Doppler effect n increase frequency
B. minimize Doppler effect n increase frequency
C. Wind magnifies Doppler effect and decrease frequency
D. Wind minimize Doppler effect and decreases the frequency.

 

[sdm33]

I am guessing wind will Wind minimize Doppler effect and decreases the frequency, because it is opposing the freq coming from the source.

 

[brood910]

No, it is D.

We have to remove the effects of wind to keep the point of reference.
In other words, we have to add the V of the wind in OPPOSITE direction to both source and observer.

The opposite direction of O to S => we gotta subtract on both numerator and denominator.

Since the source is stationary, we already know that numerator is bigger. This means the denominator will experience a bigger change when we subtract the wind speed => ratio gets bigger => f increases.

 

[sdm33]

are you saying the answer is D. Wind minimize Doppler effect and decreases the frequency.

 

[yingao88]

D makes sense to me but the answer from the back of the book says it is A. And I don't have a clue on what they saying.

 

[Postictal Raiden]

In the absence of the wind, the frequency must increase since the observer approaches the source. However, wind is blowing in the opposite direction to the direction of the frequency emitted by the source. Therefore, the wind must decrease the frequency.

I think it's D and EK solution is wrong.

 

[sazerac]

No, the wind decreases the wavelength. The waves will be smooshed together. And therefore the frequency will increase even more.

The book is correct.

 

[sdm33]

well if the wind on the same direction then it will decreases the wavelength. The waves will be smooshed together. And therefore the frequency will increase even more.

 

[Temperature101]

This question is weird... I miss all of them with wind being added to the doppler equation...Can someone clearly explain the effect of wind to the doppler equation?