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Change guitar string tension and vibration

  1. Feb 8, 2012 #1
    Change in guitar string tension - Please help?

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

    A particular guitar string is supposed to vibrate at 220 Hz, but it is measured to actually vibrate at 225 Hz. By what percentage should the tension in the string be changed to get the frequency to the correct value? Do not enter units.


    2. Relevant equations

    f= (1/2L)√(T/μ)

    I solved for 1/2L and got
    f1/(√T1) = f2/(√T2)
    f1/(√T) = f2/(√kT)

    Cancel the √T's, and you're left with
    f1/f2 = 1/√k


    3. The attempt at a solution

    I took
    f1 = 225 Hz
    f2 = 220 Hz

    k = (f2/f1)^2
    k = (220/225)^2
    k = 0.956049

    1-k = 0.04395
    Meaning you'd have to change the string by 4.395%

    But this is not the right answer.

    So far, I've tried the following and none of them have been correct.
    4.40
    4.60
    4.80
    4.39

    Can anyone please instruct me on what I'm doing wrong?
     
    Last edited: Feb 8, 2012
  2. jcsd
  3. Feb 8, 2012 #2

    vela

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    Did you try it with a negative sign?
     
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