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Homework Help: Weight of an Object on another Planet

  1. Apr 15, 2015 #1
    1. The problem statement, all variables and given/known data
    How much would a 1 kg mass weigh on the surface of a very dense planet with the same mass as Earth, but 1/2 Earth's radius?

    2. Relevant equations
    Eg(universe) = -G[(m1m2)/d^2]
    Earth's Radius = 3,959 mi
    Earth's mass = 5.97E24 kg
    3. The attempt at a solution
    If I plugged in those number into the universe gravitational energy equation along with the 1kg mass, will I get the answer in Newtons as the weight on that planet?
    Because of the negative sign in front of that equation, the answer would be in negative? Is that possible?
  2. jcsd
  3. Apr 15, 2015 #2


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    You do not need to know the radius nor the mass of the Earth to solve this problem. Simply take the ratio of the weights.

    The minus sign simply tells you the direction of the gravitational force, positive being away from the source.
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