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Homework Help: Wave movement

  1. Apr 13, 2009 #1
    1. The problem statement, all variables and given/known data
    A hiker shouts toward a vertical cliff 735 m away. The echo is heard 4.00 s later.
    (a) What is the speed of sound of the hiker's voice in air?
    [] m/s
    (b) The wavelength of the sound is 0.732 m. What is its frequency?
    [] Hz
    (c) What is the period of the wave?
    [] ms

    (taken from webassign)

    2. Relevant equations

    I would have thought it was V=d/s, but it doesn't work that way with this wave problem. Do I need to know the speed of sound?

    3. The attempt at a solution

    I took 735/4 but it told me it was the wrong answer. I'm pretty sure I could figure out the rest of the problem if I could find velocity, so any help with that?

    While I'm at it though
    1. The problem statement, all variables and given/known data
    Water waves in a shallow dish are 5.5 cm long. At one point, the water moves up and down at a rate of 5.5 oscillations per second.
    (a) What is the speed of the water waves?
    [] m/s
    (b) What is the period of the water waves?
    [] s

    Similar to the last problem, but I'm really clueless for this one.

    I have until midnight to get these problems finished, so quick help would be appreciated. I don't even need the answer necissarily, just a way of solving it. Thanks
  2. jcsd
  3. Apr 13, 2009 #2
    For him to have heard the echo, the sound has to hit the wall and then come back and hit him... so... maybe 4seconds isn't the time you should be using...
    Last edited: Apr 13, 2009
  4. Apr 13, 2009 #3
    The distance travelled by the wave is not 735 meters. That is the distance to the cliff. From this, find how far the wave travels during the four seconds that it takes for the shout to return to the hiker.
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