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Homework Help: Simple Harmonic Motion

  1. Nov 9, 2008 #1
    Simple Harmonic Motion- Spring problem

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

    A 12.5 kg mass is suspended on a 1e^5 N/m spring. The mass oscillates up and down from the equilibrium position
    [tex]y(t)= Asin(wt+\phi)[/tex]

    Find the amplitude of the oscillating mass

    Initial position- 4.9 cm
    Initial velocity= +8.64 m/s
    Time= 0

    2. Relevant equations
    No idea, see below

    3. The attempt at a solution
    Ok, I found the frequency, which is 89.44 1/s. But, I don't know how to figure out the amplitude of this thing with the information given. I've looked, and I can't find a formula to use. If someone could show me what formula I'm supposed to use, it would be greatly appreciated.
    Last edited: Nov 9, 2008
  2. jcsd
  3. Nov 9, 2008 #2
    Ok, I figured out the amplitude and the phi. But, here's the latest part of the question

    Calculate teh position @ t=.0149 seconds

    If A=10.83 cm
    w= 89.44 (1/s)
    Phi= 26.895 degrees

    Plugging that into the equation, I get 6.993, yet the system says it's wrong. It also says to answer in cm, but I'm not seeing any discrepencies here. >.>
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