1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Submarine sonar doppler problem

  1. Oct 22, 2011 #1
    1. The problem statement, all variables and given/known data

    A stationary destroyer is equipped with sonar that sends out pulses of sound at 49.0 MHz. Reflected pulses are received from a submarine directly below with a time delay of 60.0 ms at a frequency of 48.966 MHz. If the speed of sound in seawater is 1.58 km/s, what is the depth of the submarine? What is the magnitude of the submarine's vertical speed?

    r or Vs = 1.58 km/s
    t = .06s

    2. Relevant equations

    d = rt
    fL = fS(Vs + VL)/(Vs + VSource)

    3. The attempt at a solution

    I found the first part simply by using d = rt. And because that is the distance of the sonar wave to the submarine and back to the destroyer I divided the answer by 2 and got the answer of 47.4 meters.

    For the second part, I am fairly certain this is doppler problem and when I solved for VL I got the answer of 1.096 m/s which was wrong. Any hints for how to go about solving for the vertical velocity of the submarine?
  2. jcsd
  3. Oct 22, 2011 #2


    User Avatar
    Homework Helper

    I got the same answer. I see only 3 digit accuracy in the given speed of sound; answer should be rounded. Perhaps you need to round it off to 1.1 to get it correct. The accuracy of the frequency is in question. 49.0 suggests 3 digits but 2 of these are lost in subtraction so if 49.0 is properly stated there is no more than 1 digit accuracy.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook