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Homework Help: Standing waves and tension

  1. Apr 20, 2015 #1
    1. The problem statement, all variables and given/known data
    A string is held under tension, with both ends fixed, and has a fundamental frequency of 250 Hz. If the tension is doubled, what will the new frequency of the fundamental mode be?

    2. Relevant equations

    3. The attempt at a solution
    I don't know how tension can affect the equation v=ƒλ. I re-read the chapter twice still couldn't find it.

    (Ans: 354 Hz)
  2. jcsd
  3. Apr 20, 2015 #2


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    Hello Sushi, welcome to PF :smile: !

    Perhaps you can google "vibrating string" ?
  4. Apr 20, 2015 #3
    According to my physics book, the tension affects the speed of sound in the string.
    A useful equation is: v = (F/(ρ⋅A))^(1/2)
    where F = tension
    ρ = density of string
    A = cross section area of string :)
  5. Apr 20, 2015 #4


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    Looks good to me ! Even better: it matches what one finds, e.g. here

    Hey, wait a minute ! We're supposed to help folks find the answers by themselves, not just dump them on a plate !
  6. Apr 21, 2015 #5
    I'm sorry, but my jugment was simply that revealing a, for the asker unknown, equation was a way to help him/her in solving the actual problem.
    In my opinion it might be hard to know what to search for without knowing what you look for. And physics is after all about problem solving and not google-searching skills, at least it is for me.

    However, I'm sorry and will do my best to avoid helping people like this in the future! :)
  7. Apr 21, 2015 #6
    What is the derivation of it?
    Simply putting values in a formula is not physics.
    Although it is OP duty to ask meaning of an equation,
    But interest is developed in young guys when one explains them in a proper way.
  8. Apr 22, 2015 #7
    Thank you all, I know how to solve it now ^^

    It's just funny I don't see this formula in the textbook.
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