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Homework Help: Springs & Energy

  1. Dec 10, 2014 #1
    1. The problem statement, all variables and given/known data
    Hello, I'm having an issue with a question I have all the numbers and everything but I cant quite get the answer correctly and its very frustrating..

    A mass, m is held at UEP of a vertical spring constant k & allowed to fall. Calculate:
    a) The maximum stretch(max bottom)
    b) The amplitude of vibration

    2. Relevant equations
    PEg + PEe + KE= PEg' +PEe'+ KE'
    h = xo = mg/k

    3. The attempt at a solution
    I've solved the amplitude of vibration already im just stuck at part a) I really do not know how start please help thanks
  2. jcsd
  3. Dec 10, 2014 #2


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    You've quoted the right equations - just fill in the blanks: in terms of the desired unknown, what are the loss in gravitational PE, the gain in spring PE, and the change in KE?
  4. Dec 11, 2014 #3
    about maximum stretch
    I'm not sure but I think I think that depends on the spring ,,
    If it is in equilibrium after falling we will use the laws of conservation of energy ,
    If it is not "say it is oscillating" we shall use newton second law , because in oscillation , we can't specify the final and initial positions of the string [it would go back farther than it's initial position when it's allowed to fall]

    I'm I right ??
  5. Dec 11, 2014 #4


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    No, it's not the stretch at equilibrium we want, it's the maximum stretch, and that occurs once in each oscillation.
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