Applying Newton's Law of Gravitation
When using Newton's Law of Gravitation, keep in mind that gravity, or G, always = 6.67 x 10-11 N • m 2 /kg 2
force=( a constant x mass1 x mass2 ) / (separation distance) or F= Gm1m2 / r2
So if two objects of 1.0 kg and 2.0 kg are 1.0 m apart, then the formula works like this.
F = (6.67 x 10-11 N • m2 / kg2) (1.0 kg) (2.0 kg) / (1.0 m)2
Cancel out the like terms that cancel each other out. (1.0 kg x 2.0 kg= 2.0 kg2 ), which cancels out the kg2 on the bottom of the fraction as well as the to the top of it. The m2 on the top and bottom also cancel each other out. So, you do the actual math and come with the answer of 1.3 x 10-10N
If the portion of the equation that has to do with powers-of-ten or significant terms confuses you, see this study guide on significant numbers and this one on scientific notation. Also, be sure to consult your teacher for clarification on any portion that you are having difficulty with. Even the teachers who seem the most rigid are usually willing to lend some time to further explanation for those that are having problems understanding their studies.