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Force components between two bodies

  1. Feb 3, 2012 #1
    I am making an n-body simulator, but I'm stuck. How can I find the components of the Force acting between two bodies such as the Earth and the Sun. I know it's-

    F * Cos(theta) and F * Sin(theta) but if I don't know the angle how can I find the components?

    I'm using the diagram on this website but I'm still baffled.
  2. jcsd
  3. Feb 3, 2012 #2

    Simon Bridge

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    You can't.

    If you can encode the locations of each body, then you know the angle.
    Exploit your coordinate system.
  4. Feb 3, 2012 #3
    I don't know what language you're using, but a lot of them have an easy,built in method of putting two points into a method/function, and getting out the angle between them. Things like Java should have a class for that, it might me contained in the regular "Math" class but I'm not sure.

    You could also find the sines and cosines of the angles YOURSELF with your coordinates easily. Find the distance between your two points using the pythagorean theorem/distance formula, call it d
    Say the difference in height is h, and the difference in width is w
    (d2 = h2+w2)

    sinθ = h/d
    cosθ = w/d
  5. Feb 3, 2012 #4
    Thanks, in my search for a complex answer I forgot that I knew the positions of both of them and could easily find the angle.
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