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Homework Help: Longitudinal Waves - are they very different?

  1. Jan 24, 2013 #1
    1. The problem statement, all variables and given/known data

    A continuous sinusoidal longitudinal wave is sent along a coil spring from a vibrating source attached to it. The frequency of the source is 25vib/sec, and the distance between successive rarefactions in the spring is 24cm.

    a) Find the wave speed

    b) if the max longitudinal displacement of a particle in the spring is 3.0cm, and the wave moves in the -x direction, write the equation for the wave. Let the source be at x = 0, and displacement at x = 0 and t = 0 be zero.

    2. Relevant equations

    v = λf

    k = 2∏/λ

    ω = 2∏f

    D(x,t) = Asin(kx - ωt)

    3. The attempt at a solution

    Just looking for some clarification on everything here - the fact that it is a longitudinal wave kind of freaks me out a bit, but it should be able to be modeled the same as a transverse wave right?

    v = λf = 0.24*25 = 6m/s

    then to model the wave...

    Amplitude should be the maximum displacement of a particle, 0.03m

    k = 2∏/λ = 2∏/0.24
    ω = 2∏f = 50∏

    D(x,t) = Asin(kx+ωt) = 0.03sin(2∏x/0.24 + 50∏t)

    Is this equation correct for this longitudinal wave?
  2. jcsd
  3. Jan 24, 2013 #2


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    Science Advisor
    Homework Helper
    Gold Member

    Yes, that all looks correct. (Sound waves are longitudinal too, as are pressure waves in solids.)
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