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Homework Help: Velocity of longitudinal waves in a solid.

  1. Jan 6, 2010 #1
    1. The problem statement, all variables and given/known data
    Our lecturer gave us a general equation for velocity of waves; (where [itex]c=[/itex] wave velocity)
    [tex]c= \sqrt{\frac{\textrm{springiness}}{\textrm{massiness}}}[/tex]
    (Excuse the terms, I'd personally rather have been given the equations here..)

    So for transverse waves on a string/wire (where [itex]T=[/itex] Tension and [itex]\mu=[/itex] mass per unit length)
    [tex]c= \sqrt{\frac{T}{\mu}}[/tex]
    and for longitudinal waves in a gas (where[itex]B_{ad}=[/itex] the adiabatic bulk modulus and [itex]\rho=[/itex] density)
    [tex]c= \sqrt{\frac{B_{ad}}{\rho}}[/tex]

    Where I am stuck is longitudinal waves in a solid, I'm assuming massiness = [itex]\rho[/itex] but am unsure about springiness.

    2. Relevant equations

    3. The attempt at a solution
    So for longitudinal waves in a solid; solving for the dimensions of springiness appears to show that springiness is in Newtons but how does Force correlate to a wave through a solid, or am I missing the point completely?
  2. jcsd
  3. Jan 6, 2010 #2


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    Homework Helper

    hmm, I think you made a mistake in that unit calculation. I get Pascals (N/m^2), a unit of pressure... but I'm not sure what physical quantity that corresponds to, since solids don't really have pressure in the same sense as gasses. This is a particular area of physics in which my knowledge is sadly lacking.

    Isn't there a bulk modulus for solids?
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