"The study of the motion of particles is based upon axioms and laws of nature gained from experience, first formulated by Isaac Newton. Newton's laws were first published in his treatise Philosophiae Naturalis Principia Mathematica in 1687. Although he was in his forties when this treatise was published, Newton had formulated most of the axioms earlier and, by the age of 23, had developed calculus and the binomial theorem. Newton's first two laws deal with the motion of a single particle, while the second two laws deal with the interaction between two particles." p128

CONSTANT
SOMETHING THAT DOES NOT CHANGE FOR THE SYSTEM

FRAME OF REFERENCE
A MEASURING REFERENCE SYSTEM THAT IS USED TO SPECIFY THE POSITION OF OBJECTS

FREE FALL
THE STATE OF FALLING UNDER THE FORCE OF GRAVITY WITH NO AIR FRICTION IMPEDING MOTION

GRAVITATIONAL CONSTANT

GRAVITATIONAL CONSTANT
THE CONSTANT THAT APPEARS IN NEWTON'S LAW OF UNIVERSAL GRAVITATION. IT IS WTITTEN THE SYMBOL "G"

INERTIA
A PROPERTY OF A BODY THAT RESISTS ANY CHANGE IN MOTION. FOR TRANSLATION MOTION, MASS IS A MEASURE OF THE BODY INERTIA. IT IS HARD TO CHANGE THE STATE OF MOTION OF A HIGH MASS OBJECT. FOR ROTATION, THE MOMENT OF INERTIA OF A BODY IS A MEASURE OF BODY INERTIA.

INERTIAL FRAME OF REFERENCE
A MEASUREMENT OR SYSTEM OF REFERENCE THAT TRAVELS AT CONSTANT VELOCITY