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Changing pitch in frequency ratio?

  1. Jan 1, 2015 #1
    1. The problem statement, all variables and given/known data
    Stupid Problem.JPG

    2. Relevant equations

    v=fΛ

    v=√(T/μ)

    3. The attempt at a solution
    I know I'm supposed to make an attempt, but I can make heads nor tails of this. Are they changed in a constant ratioo? Does the tension come into play?

    The answer given is 0.16m
     
    Last edited: Jan 1, 2015
  2. jcsd
  3. Jan 1, 2015 #2

    berkeman

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    What's weird too is that they are saying the frequency goes down, but decreasing string length should make the frequency go up...
     
  4. Jan 1, 2015 #3

    haruspex

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    Well, it says the ratio 4/5, which maybe should be read 4:5. It doesn't say "to 4/5".
    Mickey, tension doesn't come into it because the tension isn't changing. You quote two equations, one of which is relevant, and gives the right answer.
     
  5. Jan 1, 2015 #4
    Ohh, the only way I was picturing it was the strings being slackened or maybe a reversal of elastic elongation. :P Too much thought into a simple question.
     
  6. Jan 1, 2015 #5

    haruspex

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    Okay! Yes, it's annoying when you get locked into a misreading like that.
     
  7. Jan 1, 2015 #6
    Thanks!

    And by the way, a very happy new year to you haru! :D
    May it bring you many new experiences.
     
  8. Jan 1, 2015 #7
    For strings the frequency is given by
    f=1/2L sqroot(t/m)

    Now f is inversely proportional to length of string

    Use this relation to find the answer
     
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