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Simple harmonic motion energy conservation problem

  1. Mar 26, 2013 #1
    1. The problem statement, all variables and given/known data
    A mass m hanging on a spring oscillates vertically. If the equilibrium point of the oscillation is a distance d below the relaxed length of the spring and if the amplitude of the oscillation is A, what is the maximum kinetic energy of the oscillation?


    2. Relevant equations



    3. The attempt at a solution
    I did this:
    mg=kd [itex]\rightarrow[/itex] k=[itex]\frac{mg}{d}[/itex]
    [itex]\Delta[/itex]E=[itex]\frac{1}{2}[/itex]k[itex](A+d)^{2}[/itex]-[itex]\frac{1}{2}[/itex]k[itex]d^{2}[/itex]=[itex]\frac{1}{2}[/itex][itex]\frac{mg}{d}[/itex]([itex]A^{2}[/itex]+2Ad)
    which wasn't the answer, but i don't know where i went wrong.
    if anyone could point out the problem, i'd really appreciate your help
     
    Last edited: Mar 26, 2013
  2. jcsd
  3. Mar 26, 2013 #2

    TSny

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    There's another form of potential energy that needs to be taken into account.
     
  4. Mar 26, 2013 #3
    which is?
     
  5. Mar 26, 2013 #4

    TSny

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    Note that the mass is moving vertically. Think about all of the forces acting on the mass.
     
  6. Mar 28, 2013 #5
    Thank you very much, TSny, for your help, I get it now.
    and this question wasn't supposed to have been posted here, sorry for the mix up.
     
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