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Homework Help: Sound Waves of earthquake

  1. Nov 27, 2006 #1
    When an earthquake occurs, two types of sound waves are generated and travel through the earth. The primary, or P, wave has a speed of about 8.0 km/s and the secondary, or S, wave has a speed of about 4.5 km/s. A seismograph, located some distance away, records the arrival of the P wave and then, 88.7 s later, records the arrival of the S wave. Assuming that the waves travel in a straight line, how far (in terms of m) is the seismograph from the earthquake?

    I really don't know how to approach this problem

    We skipped around chapter wise and I think I'm missing some important information from previous chapters regarding this problem.

    The only logical equation that I think might be applicable to this problem is v = sqrt(ykT/M). Are there some crucial givens that I'm over looking?

    I really just need some hints as to how to approach this problem

    Thanks a lot
  2. jcsd
  3. Nov 27, 2006 #2


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    The waves both travel the same distance, but in different times. Write the equations relating the time to the distance for each wave and solve each one for t. Subtract to get an equation for the time difference.
  4. Nov 27, 2006 #3
    Perhaps a simple kinematics equations approach is what you are looking for. No use in complicating things. Thats all it really is.
  5. Nov 28, 2006 #4
    I got it :)
    Last edited: Nov 28, 2006
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