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Homework Help: Gravitational force calc

  1. Mar 14, 2010 #1
    1. The problem statement, all variables and given/known data

    The mass of the sun is 332800 times that of the mass of Earth. The mass of neptune is 17 times that of the mass of the Earth. If the average orbital radius (distance from the sun) of neptune is 4503.99 x109 m, calculate the average gravitational force that neptune experiences due to the sun. Express your answer in units of 1021 N.
    (The gravitational constant is 6.67 x 10^-11 N m2/kg2 and the mass of Earth is 5.98 x10^24 kg.)


    3. The attempt at a solution

    ok so i set up the problem like this..

    (6.67 x 10^-11)(1.0166 x 10^26)(1.99 x 10^36) all over
    (4503.99 x 10^9)^2

    = 6.67 x 10^20 - which is wrong; ive used 1/3 tries on lon-capa and i kinda wanna know what im doing wrong here..

    ** to get the mass of the sun and neptune i just times them by the mass of earth (5.98 x10^24)(17) for neptune and (5.98 x10^24)(332800) for the sun
     
  2. jcsd
  3. Mar 14, 2010 #2
    the answer is given as

    something x10^21 N
     
  4. Mar 14, 2010 #3
    solved it.. thanks for no help
     
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