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Homework Help: Free fall and distance

  1. Jul 25, 2017 #1
    1. The problem statement, all variables and given/known data
    A stone falls from top of a well, 10 seconds later sound of water splash reaches the top of the well. How deep is the well?

    g=9.82m/s2, vsound=340m/s , t=10s

    2. Relevant equations

    s=vt , v=a0+at , s=v0t+1/2at2

    3. The attempt at a solution
    I'm stuck. I know the distance of the soundwaves traveling from the bottom to the top of the well is given by s=vt. And the distance the rock travels is given by s=v0t+1/2at2.

    Do i try figure out for how long the rock travels before hitting the bottom?, Or are equations supposed to be merged? Please point me in the right direction :)
  2. jcsd
  3. Jul 25, 2017 #2
    You already have s=v0t+1/2at^2
    In this case, the initial velocity is 0, so the distance is s=1/2at^2.
    For the sound return, s=340m t.
    So you need your two s's to be equal and your two t's to add to 10 seconds.
  4. Jul 25, 2017 #3


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    Use t in one of the equation for motion, and (10 - t) in the one for sound. Set the distances equal to each other. Once you have t, you can find the distance in the usual fashion.
  5. Jul 26, 2017 #4
    Thank you! Excellent help gentlemen, i fully understand now.
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