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Homework Help: Universal Gravitation Problem

  1. Jan 19, 2015 #1
    1. The problem statement, all variables and given/known data

    Three point particles are fixed in place in the xy plane. The three partiles sit on the
    corners of an equilateral triangle with sides of length a = 2.50 mm. Particle 1 has a mass m1 = 12.0 kg,
    particle 2 has a mass m2 = 18.0 kg, and particle 3 has a mass m3 = 15.0 kg.

    1. What is the magnitude and direction of the net gravitational force exerted on particle 1 by the other
    two particles?

    2. Relevant equations



    3. The attempt at a solution
    I'm trying to use the above equation and separate them by its x and y components. But I feel that because its an equilateral triangle I need to somehow make it into a right triangles so that the radius from mass 1 of both particles will be 30 degrees from mass 1 if I make mass 1 the origin.

    How do I attack this problem?
  2. jcsd
  3. Jan 19, 2015 #2


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    Staff: Mentor

    You have 2 forces acting on particle #1. You know these 2 forces act with an angle of how many degrees between them?

    Draw the diagram.
  4. Jan 19, 2015 #3


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    Homework Helper

    probably easiest to add the components ... it is the same thing as splitting the equilateral into 2 right triangles.
    put mass 1 at the tip of the A , there's only 1 component.
  5. Jan 20, 2015 #4
    Sorry, I forgot to mention I did. I drew what forces acted on mass 1 as well.
  6. Jan 20, 2015 #5
    Where I am drawing a mental blank is if I divide it into two right trianges I get that a sides are the hypotenuse and the opposite angle of mass 1 is !/2a but the how do I find the adjacent side to mass 1?

    Attached Files:

    • hw1.pdf
      File size:
      168.8 KB
  7. Jan 20, 2015 #6


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    Staff: Mentor

    Doesn't Pythagoras help you with right triangles?
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