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Gravitational pull on two objects

  1. Feb 21, 2009 #1
    If three balls (all weighing 2.0kg) are lined in a row, what is the magnitude of the net gravitational force on mass A due to masses B and C in the figure. B is 10cm from A, and C is 50 cm from A (and of course C is 40 cm from B)
    (here's a 'diagram')
    (A)----(B)----------------------------C
    I've been using the equation G*(m1m2/Rsq) and been adding the gravitational pull from a & b and a & c but for some reason that's wrong. So where do I need to fine tune my equation?
     
  2. jcsd
  3. Feb 21, 2009 #2

    D H

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    What answer do you get? What do you expect to get (i.e., why do you think you are wrong)? Show your work, please.
     
  4. Feb 21, 2009 #3
    I'm expecting to get 3.00×10-9 due to, the fact that G*(2kg*2kg)/.1m + G*(2kg*2kg)/.5m = 3.00×10-9
     
  5. Feb 21, 2009 #4

    D H

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    You aren't using Newton's formula for gravitation. Look the equation, then look at what you are doing.
     
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