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Frequencies on a violin string

  1. Jun 14, 2010 #1
    A violin string has a length of 0.350 m and is tuned to concert G, with fG = 392 Hz.
    Where must the violinist place her finger to play concert A, with fA = 420 Hz?

    If this position is to remain correct to half the width of a finger (that is, to within 0.600 cm), what is the maximum allowable percentage change in the string tension?

    Ok so I already figured out the first question, the position to play concert A is 32.6666... cm from the bridge. I obtained this answer from dividing the equations, canceling, and solving.
    It is the algebra of the second part that is giving me trouble, and I am not sure how to approach it. I am sure it too has to be done by dividing two equations for the frequencies and ending up with with a ratio of the two tensions. I just can't seem to get it.

    I really need the answer by 5:00PM Central time, don't know if anyone will be able to solve it, but I'd appreciate any help.
     
  2. jcsd
  3. Jun 14, 2010 #2

    uart

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    So this is homework then?

    Anyway start by figuring out :

    1. What percentage change 0.6cm corresponds to at 32.67cm. Then

    2. Figure out how (what function of) does the frequency vary with tension.

    3. Find the percentage change in tension corresponding to the same percentage change you just calculated in part 1.

    Hint : Frequency is NOT a linear function of tension.
     
  4. Jun 14, 2010 #3
    Thank you for the quick reply. That's the direction I was going in, was just having some trouble. Got it now. And yes, it is sort of homework I guess. More like some general problems to help out with a project.
     
  5. Jun 14, 2010 #4

    uart

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    Hi Corey. Did you get that the frequency is proportional to the square root of tension? That's important in this problem.
     
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