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Homework Help: Speed of a ball launched from a spring

  1. May 26, 2008 #1
    1. The problem statement, all variables and given/known data
    The force required to compress an imperfect horizontal spring an amount x is given by F = 150x + 12x^3, where x is in meters and F in newtons.
    If the spring is compressed 2.5m, what speed will it give to a 3.5kg ball held against it and then released?
    2. Relevant equations
    Not sure all these are relevant, but...
    F = ma
    a = dv/dt
    K = mv^2 /2

    3. The attempt at a solution

    I made many attempts and the computer told me that none were right.

  2. jcsd
  3. May 26, 2008 #2


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    Staff Emeritus
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    Gold Member

    Welcome to PF cilantrone,

    Just looking at the relevant equations that you have listed, I notice that there is a vital one missing, the definition of work.
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