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Homework Help: Circular Motion

  1. Nov 22, 2004 #1
    A spacecraft leaves Earth to travel to the moon. How far from the centre of the Earth is the spacecraft when it experiences a net force of zero?

    Can anyone help me with this?

    Thanks.
     
  2. jcsd
  3. Nov 22, 2004 #2

    Galileo

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    Draw an axis. Place the centre of the Earth at x=0 and the centre of the moon at x=R.
    Then the gravitational force on a spacecraft of mass m at x between 0 and R is:

    [tex]F=F_{earth}+F_{moon}=-G\frac{M_{earth}m}{x^2}+G\frac{M_{moon}m}{(R-x)^2}[/tex]
     
  4. Nov 22, 2004 #3
    Thanks for that :)
     
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