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 problem

  1. Aug 31, 2005 #1
    Hi,

    I need to solve this problem but I have no idea where to start. I made a little drawing with all the informations I have but now I'm stuck. Here's the problem:

    A submarine uses sonar waves, to identify other ships, by directing a highly directional acoustic pulse at a target, and computing the time duration between the transmission of the "ping", and the return of the echo. If a sub is a depth of 500m and receives a ping return in 5.6s, determine the direct distance to the ship.

    I'm not looking for the answer, just a little hint of what to start with. Thanks alot !

    - alex.
     
  2. jcsd
  3. Aug 31, 2005 #2

    Doc Al

    User Avatar

    Staff: Mentor

    What's the speed of sound in water? How far must the sound have traveled in 5.6s? (Don't forget that the sound makes a round trip.)
     
  4. Aug 31, 2005 #3
    Great ! Thanks. One last question, does the temperature affects anything ? Thanks !
     
  5. Aug 31, 2005 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Both pressure and temperature will affect the speed of sound. (But I'll bet you can ignore such complications.)
     
  6. Aug 31, 2005 #5
    The problem actually include the temperature, so I guess I need to include it in my formula. I google'd for it but could only find tables. If density of water is 1, what formula should I use ?

    Thanks !
     
  7. Aug 31, 2005 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Unless this problem is meant to exercise your detailed understanding of the speed of sound in a liquid (the speed depends on the bulk modulus and density, which in turn depend on pressure and temperature), I would just look up the speed of sound (in seawater... salinity counts!) at some standard temperature. That should be good enough.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook