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Homework Help: Application of double integrals: density

  1. Apr 14, 2010 #1
    1. The problem statement, all variables and given/known data

    The boundary of a lamina consists of the semicircles y = sqrt(1-x^2) and y = sqrt(4-x^2) together with the portion of the x-axis that join them. Find the center of mass of the lamina if the density at any point is proportional to its distance from the origin

    2. Relevant equations

    3. The attempt at a solution

    I have a hard time getting y and x boundaries, plus the function thats going to be integraded..
    I understand that the function found be the distance from (0,0).. but how can I express that mathematically? I'm thinking that it could be simply sqrt(x^2+y^2), since x and y for a right trinagle, with hypotenuse being the distance to the point..

    But with the boundaries - I'm completely lost.. help! :(
  2. jcsd
  3. Apr 14, 2010 #2
    Ok, never mind. I got it :) Forgot about the polar coordinates..
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