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Homework Help: Universal Gravitation questions

  1. Oct 3, 2005 #1
    1) if something is 5 earth radii above the earth's surface and you know its mass, how would you figure out force of gravity on it?

    2)and given the radius and mass of a planet how would you be able to figure out the acceleration due to gravity on it?
  2. jcsd
  3. Oct 3, 2005 #2
    a_{grav} = \frac{GM}{r^2}

    where G is the gravitational constant, M is the mass of the planet, and r is the distance from the center of the planet.
  4. Oct 3, 2005 #3
    that won't work for the first question...the object is a spaceship and there is nowhere in that equation to plug in its mass...
  5. Oct 3, 2005 #4
    nevermind i figured it out myself...thanks
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