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Homework Help: Calculate the distance of the ship from the island

  1. Dec 17, 2008 #1
    1. The problem statement, all variables and given/known data
    This is a pretty challenging question... if someone could solve it and confirm my answer I would appreciate it.

    The survivor of a shipwreck lands on an island which is 3000 m from a vertical cliff.
    He sees a ship anchored between the island and the cliff.A blast from the ship's horn is heard twice with a time lapse of 4 seconds.Calculate the distance s of the ship from the island.(Assume that the speed of sound is 330 m/s )

    2. Relevant equations

    3. The attempt at a solution

    I'm getting 840 m.... if someone has a difference answer please let me know how you did it.
    And try to make it as simple as possible.. just a HS question
  2. jcsd
  3. Dec 17, 2008 #2


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    Homework Helper

    Welcome to PF.

    Perhaps you can explain how you arrived at that number?
  4. Dec 17, 2008 #3
    Well actually now I'm starting to believe that isn't correct anymore.
    This is how I am doing it now.

    6000-s over 330 - s over 330 = 4

    With this I'm arriving at a different solution, which I think is correct.
  5. Dec 17, 2008 #4
    Draw a picture.

    You said the survivor hears the horn twice. If the sound was heard twice, how did this happen?

    On your diagram, draw the path that the sound must take for both the first and the second blasts.

    Obviously the second blast had to travel further if it got there later. How much further did this second blast need to travel??
  6. Dec 17, 2008 #5


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    If you were standing on the boat, and you rang the bell, when would you hear the echo? At 330m/s how far away from you would the cliff be at that point?
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