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Homework Help: Elasticity in colloids (gels, jellies)

  1. Mar 15, 2004 #1
    I have a question on finding elasticity of colloids.

    I am using Ultrasonics testing on testing the different elasticity of gelatine with different concentrations of additives, ie, salt, sugar.

    From the ultrasonics data, I calculated the attenuation coefficient and the velocity (speed of sound) of the gelatine.

    there is an equation related to the modulus of elasticity:

    V= sqrt (C/P)

    where V is the speed of sound, C is the elastic constant and p is the density.

    however, I dont know the denisty of the sample I tested. So, is there other ways to calcuate the density with the attenuation coef and velocity? or is there another formula that can solve my problem?

    Please help....:(
  2. jcsd
  3. Mar 15, 2004 #2


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    Science Advisor

    It should be simple to calculate the density of your sample- I suspect that "additives" like salt, sugar, etc. won't noticably affect the average density so you might get away with just taking a sample of your gelatin, finding its volume and mass and dividing!

    I would recommend making up a new batch with the additives and doing the same just to be sure that the density hasn't changed significantly.
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