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Homework Help: Calculating Qfactor

  1. Sep 4, 2009 #1
    1. The problem statement, all variables and given/known data
    "Systems typically exhibit an exponential decrease in their average stored energy of the form <E> = E[tex]_{0}[/tex] e^(-vt) ---- If a piano key of frequency 256 Hz is struck and its oscillation energy decreases to one half of its initial value in about 1 second what is the effective Qf of the system?

    2. Relevant equations

    Qf = w/v
    <E> = E[tex]_{0}[/tex] e^(-vt)

    3. The attempt at a solution

    I need to find the energy dissipated and from the equation they gave me I put 1/2 (the energy the system has from its initial value after 1 second)

    1/2 = e^(-v)

    v = .693

    Qf = 256/.693 = 369

    I'm not quite sure if I did the dissipation energy equation correctly.
  2. jcsd
  3. Sep 4, 2009 #2
    [tex] Q=\frac{\omega}{v}=\frac{2 \pi f}{v} [/tex]. Your numerator needs to be in angular frequency. Looks fine though.
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