1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Doppler Effect of submarines

  1. Jan 29, 2006 #1
    I'm working on the following problem:

    Two submarines are underwater and approaching each other head-on. Sub A has a speed of 4 m/s and sub B has a speed of 18 m/s. Sub A sends out a 1010 Hz sonar wave that travels at a speed of 1522 m/s.

    The question asks two questions, but I'm stuck on the first one:

    What is the frequency of the sound detected by sub B (to the nearest Hz)?

    I was using the formula frequencyobserver = frequencysource * 1 + (vobserver / velocity of sound) / 1 - (vsource / velocity of sound). I assumed that the numerator would use the positive sign since the observer is moving towards the source. I used the minus sign in the denominator since the source is moving towards the observer. For the speed of sound I used 1522 m/s since the submarines are travelling in salt water. I then multiply my calculated numbers times 1010 and got a frequncy of 1019 Hz. However webassign is telling me this is incorrect. Any help with what I'm doing wrong?
  2. jcsd
  3. Jan 29, 2006 #2
    Maybe you pluged in wrong data. Your equation looks correct to me.

    [tex] f' = f \frac{v+v_D}{v-v_S} [/tex]

    [tex] v= 1522 m/s [/tex]

    [tex] v_D = 18 m/s [/tex]

    [tex] v_S = 4m/s [/tex]

    And my answer is f'=1024.6 Hz
  4. Jan 29, 2006 #3
    My goodness, that thing was too picky. I put in 1023 Hz the first time and it didn't accept the number. Thank you for your help.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Doppler Effect of submarines
  1. Doppler effect (Replies: 3)

  2. The Doppler Effect (Replies: 3)