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What is the gravity of a planet 2 times the radius and 3 times the mass of earth

  1. Oct 3, 2012 #1
    what is the gravity of a planet 2 times the radius and 3 times the mass of earth
     
  2. jcsd
  3. Oct 3, 2012 #2

    SammyS

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    Re: gravity

    Hello cmbswim89. Welcome to PF !

    Do you mean, "What is the acceleration due to gravity on the surface of a planet 2 times the radius and 3 times the mass of earth?"

    Show us what you have tried, and where you're stuck so we can help you.
     
  4. Oct 3, 2012 #3
    Re: gravity

    well the problem states a person weighs 540N on earth and asks how much he weighs on a planet 2 times the radius and 3 times the mass. i have tried putting that data into the gravitational force equation but multiplying earths mass by 3 and radius by 2 but i don't get any of the multiple choice questions i have
     
  5. Oct 4, 2012 #4

    SammyS

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    Re: gravity

    What equation are you putting the mass & radius into ?

    What do you get?
     
  6. Oct 4, 2012 #5
    Re: gravity

    F=G(3(m1))(m2)/2r2 so it looks like that with m1 as earths mass and r as earths radius and i get 793.18N
     
  7. Oct 4, 2012 #6

    SammyS

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    Re: gravity

    Are you using (2r)2 or 2(r2) in the denominator?
     
  8. Oct 4, 2012 #7
    sr^2 sorry
     
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