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Homework Help: The z coordinate of the center of mass of the box

  1. Feb 21, 2008 #1
    1. The problem statement, all variables and given/known data
    A cubical box has been constructed from uniform metal plate of negligible thickness. The box is open at the top and has edge length L = 97 cm. Find (a) the x coordinate, (b) the y coordinate, and (c) the z coordinate of the center of mass of the box.

    2. Relevant equations

    3. The attempt at a solution
    I could not figure out what to do with a three dimensional object since we are not given a mass.
  2. jcsd
  3. Feb 22, 2008 #2

    Shooting Star

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    Assume some [itex]\sigma[/itex] as the two dimensional mass density, that is, mass per unit area of the faces. Multiplying [itex]\sigma[/itex] by area, you'll get the mass. I think you know where the CM of a rectangle is. Now, apply the formula you know.
  4. Feb 22, 2008 #3


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    If you assume that the mass of one side is M then the com of the four upright sides will correspond to a "particle" of mass 4M in the middle of the box. You now need to combine this with a "particle" of mass M in the middle of the bottom to get the overall com.
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