ISCI 1A24 Lecture Notes - Lecture 4: Orbital Period, Ellipse, Inverse-Square Law
17 Sep 2017
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Orbit: continually falling to the ground, you are in free fall, this is what satellites do. Force keeping an object in orbit: gravity keeps the object in orbit, f = mg but g can change on different planets . Newton"s general law of gravity: reasoned that gravity might be a universal force between any two masses. The strength of the force of gravity must be: proportional to each mass, m1, m2, proportional to 1/r2 where r is the distance between them (inverse-square law) Putting this in equation form; fg is proportional to m1*m2/r2. *g is the universal constant = 6. 6784 * 10^-11 m3/kgs2. Newton could immediately use this concept toa accurately explain the motions of the. A revolutionary step in science: the moon (or any satellite) is in free fall around the earth, at the distance r of the moon : g = g m / r2 (much smaller than at earth)
