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Trying to solve newtons equation.....

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I tried doing this equation. http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation


Using the Earth Moon system.


So I did it and got this number, 1.961512E247.


From these numbers, G= the gravitational constant, M earths mass, M2 Moons mass, and r^2 as the distance between the earth and the moon, which is 348, 403 km. I divided this all and got that humongous number.


Is it wrong? Am I doing something wrong?



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There are two common mistakes high school students and freshmen make in solving these kinds of problems. Since your exponent is way off its hard to tell. These mistakes are

  • Not using the correct value for G, the Earth's mass, etc. G is 6.673×10-11 m3/kg/s2. Note well: G has units. It is a physical constant. Solar system astronomers might well use 1.488×10-34 AU^3/kg/day^2.
  • Treating physical constants such as G and physical values such as the Earth's mass and the Earth-Moon distance as numbers. Don't do that! The number one sign that students are doing that is stating the result without units. Always carry the units along with you in your calculations.

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