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Homework Help: Centre of gravity of this system of particles

  1. Feb 3, 2010 #1
    1. The problem statement, all variables and given/known data

    Find the centre of gravity of this system of particles



    2. Relevant equations

    attached image showing diagram

    http://www.zshare.net/image/7209360586277b98/ [Broken]





    3. The attempt at a solution

    Taking moments about a, 4*0+6*30 = 184 then not sure

    Any help is greatly appreciated

    Thanks in advance
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 3, 2010 #2

    HallsofIvy

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    Science Advisor

    Don't worry about moments- take a "weighted" average of the components. Taking the 4 kg mass on the left to be at (0, 0), the 6 kg mass is at (30, 0) and the 8 kg mass at (30, -14). The x-coordinate of the center of mass will be at
    [tex]\frac{4(0)+ 6(30)+ 8(30)}{4+ 6+ 8}[/tex]
    and the y-coordinate will be
    [tex]\frac{4(0)+ 6(0)+ 8(-14)}{4+ 6+ 8}[/tex]
     
  4. Feb 3, 2010 #3
    Thanks for the reply, ok so I get 23.33 for x and -6.22 for y,

    Providing I have calculated the sums correctly,
    the minus is throwing me off in locating the centre?

    Thanks again!
     
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