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Homework Help: Shm homework

  1. Dec 19, 2006 #1
    1. The problem statement, all variables and given/known data

    What is the maximum acceleration of a platform that oscillates with an amplitude of 2.70 cm and at a frequency of 6.40 Hz?

    2. Relevant equations

    [tex]a(t)=-\omega^2x_m\cos{(\omega t=\phi)}[/tex]

    [tex]\omega=2\pi f[/tex]

    3. The attempt at a solution
    a(t) will be maximized when a'(t)=0 (or when cosine's argument=1; it works out exactly the same).

    So I want [tex]\omega t +\phi=0 or \pi[/tex]. I can shove in (2)(pi)(f) for omega no problem, but I'm stuck with the flipping phase constant. Can I just assume that it's zero??
    Last edited: Dec 19, 2006
  2. jcsd
  3. Dec 19, 2006 #2
    Why do you care about what's in the cosine? Just set the cosine equal to one - you know that's the maximum value of the cosine function - and plug into the remaining parts of your acceleration expression.

    So you would just need to know that [tex]a_{\mathrm{max}}=\omega^2x_m[/tex] (Note that the cosine is gone because we set it to unity).
  4. Dec 19, 2006 #3
    right... :redface: thenks.
    Finals approach and my brain is fried lalalalalalala.Yes, there is a cause-and-effect going on here, although I am not telepathetic (but I do have dark hair...) AAAACK!
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