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Wave speed and length

  1. Feb 3, 2014 #1
    1. The problem statement, all variables and given/known data

    A long string with a mass/length of 500g/m is placed under a tension of 400N. The string is then vibrated up and down with a period of .425sec.

    What is the wave speed?

    What is the wavelength of the resulting wave?

    I have no idea where to beginI would really like to learn this. It's been 20+ years since I have taken a Physics course.
    Thank you!


    2. Relevant equations



    3. The attempt at a solution

    I have no idea where to begin other than this formula:

    v=λ/T

    I would really like to learn this. It's been 20+ years since I have taken a Physics course.
    Thank you!
     
  2. jcsd
  3. Feb 3, 2014 #2

    lightgrav

    User Avatar
    Homework Helper

    what resource are you using? (textbook, on-line notes, ??)
    ...(here are some very brief notes : http://www.science.marshall.edu/foltzc/211t9.htm )

    generally to get a speed, you square root a (Force term divided by an inertia density).
    tweak the density so that the units come out right for speed.

    sqrt[T/(m/L)].
     
  4. Feb 3, 2014 #3
    I did use v=sqrt[T/(m/L)]

    so I got v=sqrt[400N/(500g/m)] = .029

    Am I on the right track???
     
  5. Feb 3, 2014 #4
    Changed my g to kg. Thank you so so much for confirming.
     
  6. Feb 3, 2014 #5
    No. You have made error in calculating square root.
     
  7. Feb 4, 2014 #6

    lightgrav

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    Homework Helper

    right track, but off by a UNITS error ... recall that Newton is composed of kilo-gram, not gram. (N=kg m/s²)
    Always include the units that any numerical value multiplies; kg should cancel inside the sqrt.
     
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