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Homework Help: Simple Harmonc Motion

  1. Oct 18, 2005 #1
    the question is
    An object is undergoing simple harmonic motion with period T_1 and amplitude A. At t = 0 the object is at x = 0. How far is the object from the equilibrium position at time t?

    well i come up with:
    A*cos((2*pi/T_1)*t)

    but i get that theres something wrong with my trigonometry, i cant figure out what im doing wrong
     
  2. jcsd
  3. Oct 18, 2005 #2

    ZapperZ

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    Hint: if you substitute t=0, do you get x=0 with that cosine function?

    Zz.
     
    Last edited by a moderator: May 19, 2013
  4. Oct 18, 2005 #3
    Well as the object is at the equilibrium position at t = 0 there's no phase shift and the displacement is modelled as x = Asin(wt)

    The period (let's just call it T for now) = 2pi/w, therefore w = 2pi/T

    The equation for the displacement at time t then comes to x = Asin(2*pi*t/T), so unless I'm mistaken you just misread the initial conditions (if you wanted to make it into a cos expression you could give it a phase shift of pi/2).

    Cheers,
    Just some guy
     
  5. Oct 18, 2005 #4
    OMG thanks so much, i noticed the mistake, hehe, its pretty late, should be sleeping not prepping for my upcoming middies..
    Thanks guys for quick replies!
     
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