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Homework Help: Finding distance using sound

  1. Oct 3, 2005 #1
    here is the question

    Cliff Height. You are climbing in the High Sierra where you suddenly find yourself at the edge of a fog-shrouded cliff. To find the height of this cliff, you drop a rock from the top and 10.0 s later hear the sound of it hitting the ground at the foot of the cliff.

    Ignoring air resistance, how high is the cliff if the speed of sound is 330 m/s

    ok i did the problem and i just wanted at least to people to check my work.

    h = .5gt2

    time for sound to reach the person
    ts = h/vsound

    since the total time is ten seconds then i can solve both equations for time
    time for rock to hit ground
    t = sqrt(2h/g)
    time for sound to travel up to the person
    t = h/vsound

    then ttotal = sqrt(2h/g) + h/vsound

    then i can solve for h.

    I got -1086.9m and -14130.43m

    can at least two people confirm that. The reason i am asking is because I am doing my homework online and i have one more try to get it right, so i want to make sure I got it right.

  2. jcsd
  3. Oct 3, 2005 #2


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    Homework Helper

    Check your arithmetic for the quadratic.

    The answer is closer to 380 m - which you can check by substituting it into the expression you already had - ttotal = sqrt(2h/g) + h/vsound - it's correct.
    Last edited: Oct 3, 2005
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