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Homework Help: Finding mass using multiple integrals

  1. Dec 10, 2008 #1
    The density per unit area of a circular lamina of radius a varies as the cube of the distance from a single point on the edge. Find the mass of this lamina.

    im guessing id have to do ρdxdydz, and maybe use polar coordinates but im completely lost. Im used to the question giving me an equation for the density which this doesnt have.

    Any help would be much appreciated
    (This is an exam question i had today but failed miserably at!)
  2. jcsd
  3. Dec 10, 2008 #2


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    Homework Helper

    Hi nb89! :smile:

    i] you do have an equation for the density … it's the cube of that distance

    ii] in problems like this, choose suitable slices before integrating …

    in this case, arcs of thickness dr :smile:
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