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Homework Help: Gravitational potential energy

  1. Nov 5, 2007 #1
    The answer is c, but I can't figure out what is the reason, can somebody kindly explain it?
    http://tinyurl.com/32322t
     
    Last edited: Nov 5, 2007
  2. jcsd
  3. Nov 5, 2007 #2
    What do you think about gravitational potential energy of a cubical block?
     
  4. Nov 5, 2007 #3
    I am thinking about centre mass...
    So what I am figuring is
    3m*g*(3/2 l)=9/2mgl...(3/2 l because the centre of mass is at that height)
    Is it correct?
     
  5. Nov 5, 2007 #4
    perfect.
     
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