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Need help with wave

  1. Jun 18, 2012 #1
    The 3rd harmonic on a piano string occurs when a 45.0 cm wave is produced. How long is the string.

    This question is really confusing can i get some leads to help me out please and thank u
     
  2. jcsd
  3. Jun 19, 2012 #2

    CWatters

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    Make three drawings showing a string vibrating at the first, second and third harmonic.
    Hint: Third harmonic has three antinodes.

    http://en.wikipedia.org/wiki/Vibrating_string

    Mark the wave length on the drawing of the third harmonic.
    http://en.wikipedia.org/wiki/Wavelength

    The question is presumably telling you that one wavelength is 45cm.

    Apply basic maths to calculate the length of the string.

    I'll let you work it out but I make the answer a number between 60cm and 70cm.
     
    Last edited: Jun 19, 2012
  4. Jun 19, 2012 #3

    CWatters

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  5. Jun 19, 2012 #4
    OK i understand but i still don't no what formula to use.
     
  6. Jun 24, 2012 #5

    CWatters

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    No formula is required. Scale from the drawing.

    One wave length = two half wave lengths = 45cm

    So three half wave lengths = 3/2 * 45cm = 67.5cm
     
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