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Homework Help: Quadratic formula problem

  1. Apr 11, 2007 #1


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    1. The problem statement, all variables and given/known data

    A physics student with too much free time drops a watermelon from the roof of a building height H. He hears the sound of the watermelon going "splat" after a time interval of Delta T.
    You may ignore air resistance. How high is the building? The speed of sound is Vs.

    2. Relevant equations

    Quadratic formula

    3. The attempt at a solution

    Ok T = T1 +T2 = H/Vs + sqrt(2H/g)

    (T - H/Vs)^2 = 2H/g


    T^2 - (2TH/Vs) + (H/Vs)^2 - 2H/g = 0

    I want to solve for H.
    How do I plug this into the quadratic formula so that I can solve for H? Im only used to there being 3 terms in the poly nomial (like x^2 + x + 4). Im thinking I have to combine the -(2TH/Vs) and -2H/g somehow but I dont know how!!!!! Please help!
  2. jcsd
  3. Apr 11, 2007 #2


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    Homework Helper

    Yes, you combine the two terms, and take out the H. That will leave you with three terms in the form of a quadratic equation.
  4. Apr 11, 2007 #3


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    Ok I combined them and got H (-2t/Vs - 2/g)

    So tell me if this is correct

    a = 1/Vs

    b = (-2t/Vs - 2/g)

    c = t^2

    Because when I plug that in as an answer it comes back wrong.
  5. Apr 11, 2007 #4


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    Homework Helper

    One thing I see is that a should be 1/Vs^2.
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