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Homework Help: Newtons law of gravity problem

  1. Jun 24, 2014 #1
    1. The problem statement, all variables and given/known data
    Two identical rocks of mass 2 kg drift through space far from any planet or star. If they pass one another at a separation of 30 cm, what is the magnitude of the gravitational force of one rock on the other at this instant.

    2. Relevant equations
    F = G (m1m2/r2)

    3. The attempt at a solution
    (4/.32)(6.673 x 10-11) = F
    (4/.09)(6.673 x 10-11 = F
    44.444444444444(6.673 x 10-11 = F
    F = 3.804 x 10-8 N
    the actual answer is F = 2.96 x 103 N
  2. jcsd
  3. Jun 24, 2014 #2


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    Staff: Mentor

    The "actual answer" is not correct, but it is the order of magnitude that is wrong not the mantissa of the number. Perhaps you misquoted the power of ten?

    Regarding your solution attempt, your formula is fine but your math is not right. Recheck your calculation.
  4. Jun 25, 2014 #3
    OK I see my mistake and the answer I put was a typo it is actually 2.96 x 10-9 N
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