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**[SOLVED] Doppler Effect Problem**

**1. Homework Statement**

A submarine (sub 1) travels through water at a speed of 8.00 m/s, emitting a sonar wave at a frequency of 1400 Hz. The speed of sound in the water is 1533 m/s. A second submarine (sub 2) is located such that both submarines are traveling directly toward each other. The second submarine is moving at 9.00 m/s. While the subs are approaching each other, some of the sound from sub 1 reflects from sub 2 and returns to sub A. If this sound were to be detected by an observer on sub A, what is its frequency?

**2. Relevent equations:**

Doppler Equations:

Observed frequency = Actual frequency[(velocity of sonar + velocity of observer)/(velocity of sonar- velocity of source)]

Using the above equation, I found that the frequency observed by sub 2 was 1385 Hz. I noted that this frequency was also the frequency of the wave reflected off of sub 2. I substituted this frequency for the actual frequency in a new Doppler equation taking the velocity of sub B (the source) to be 0 m/s and found that the frequency observed by sub 1 was 1392 Hz. Would you please advise whether I'm correct?

I'm only asking because the textbook and my professor says I'm wrong.

Doppler Equations:

Observed frequency = Actual frequency[(velocity of sonar + velocity of observer)/(velocity of sonar- velocity of source)]

Using the above equation, I found that the frequency observed by sub 2 was 1385 Hz. I noted that this frequency was also the frequency of the wave reflected off of sub 2. I substituted this frequency for the actual frequency in a new Doppler equation taking the velocity of sub B (the source) to be 0 m/s and found that the frequency observed by sub 1 was 1392 Hz. Would you please advise whether I'm correct?

I'm only asking because the textbook and my professor says I'm wrong.

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