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Homework Help: Gravity and mass question, please help

  1. Oct 13, 2008 #1
    1Three masses are arranged in the (x, y)
    plane as shown.

    7kg at (-3,1)
    8kg at (0,0)
    9kg at (1,2)

    What is the magnitude of the result-
    ing force on the 8 kg mass at the ori-
    gin? The universal gravitational constant is
    6.6726 × 10^−11 N · m^2/kg^2 . Answer in units
    of N.

    part 2; Select the figure showing the direction of the
    resultant force on the 8 kg mass at the origin. all the mutliple choice aswers show a ray rotating a different amount around the origin

    please help, i was sick and missed 2 days of physics and dont understand even wath the question is askeing
    if you could even expain it to me it would be wonderful
  2. jcsd
  3. Oct 13, 2008 #2
    You can calculate the distances from each mass to the 8kg mass by using Pythagoras' theorem.

    Force on masses due to gravity is dependent upon each mass as well as radius.

    This is the formula: [tex] F = \frac{GMm}{r^2} [/tex]

    Use the principle of linear superposition to determine the net force.
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