Is the textbook wrong or am I?

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

    A vertical spring (ignore its mass), whose spring constant is 875 N/m is attached to a table and is compressed down by .160 m. (a) What upward speed can it give to a .380 kg ball when released?

    2. Relevant equations

    Conservation of Energy using 1/2 k x^2 for Uspring.

    3. The attempt at a solution

    I get 7.68 m/s for the velocity and the book gets 7.47 m/s. Wanted to see who was right and if I'm doing something wrong.
  2. jcsd
  3. LowlyPion

    LowlyPion 5,324
    Homework Helper

    "Upward" also means against gravity. You should also figure as an adjustment the m*g*h over the displacement of the acceleration.
  4. So you're saying you got the book's answer?

    I used the conservation of energy subbing values for spring and taking into account y=0 when crossing the original spring length. I'm quite sure I have the right answer and the book's is wrong but I just want to verify.
  5. LowlyPion

    LowlyPion 5,324
    Homework Helper

    I'm just saying that

    mv2/2 = kx2/2 - m*g*x
    Last edited: Oct 20, 2008
  6. You are wrong, your book is right, Pion is right: (except I would not use both "h" and "x", there is only one vertical distance in the problem)
  7. LowlyPion

    LowlyPion 5,324
    Homework Helper

    Thanks for the catch. Of course h and x are the same.

    I edited the previous post to be correct now.
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