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Homework Help: Macromolecules (Thermodynamics)

  1. Apr 20, 2009 #1
    1. The problem statement, all variables and given/known data

    A dilute solution of macromolecules at temperature T is placed in an untracentrifuge rotating with angular velocity w. The centripetal acceleration w2r acting on a particle of mass m may then be replaced by an equivalent centrifuge force mw2r in the rotating frame of reference.
    a) Find how the relative density [tex]\rho[/tex](r) of molecules varies with their radial distance r from the axis of rotation.
    b) Show quantitatively how the molecular weight of the macromolecules can be determined if the density ratio [tex]\rho1[/tex] / [tex]\rho2[/tex]at the radii r1 and r2 is measured by optical means.

    2. Relevant equations

    F = mv2/r

    density = mass /volume

    3. The attempt at a solution

    I do not know how to even start the problem. Please help.
  2. jcsd
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