| A | B |
|---|
| mass | amount of matter in an object |
| weight | amount of gravitational force on an object |
| gravity | attractive force between all matter |
| Sir Isaac Newton | Scientist who defined gravity and the laws of motion in the 1600's. |
| Galileo | Scientist who tested ideas about gravity in the 1500's |
| Universal Law of Gravitation | All objects in the universe attract each other through gravitational force. The force increases with the object's mass and decreases with distance. |
| acceleration | a change in velocity over time; increases with force and decreases with mass. |
| force | a push or a pull, can be balanced or unbalanced. |
| net force | sum of all forces acting on an object |
| terminal velocity | constant velocity of a falling object when air resistance is equal to the force of gravity |
| free fall | when an object is only being pulled by gravity and no other forces are acting on it |
| orbiting | when one object travels around another in space due to the force of gravity and its own speed |
| inertia | tendency of an object to resist a change in motion |
| Newton's First Law of Motion | law of inertia - - objects tend to resist changes in motion unless acted upon by an unbalanced force. |
| Newton's Second Law of Motion | The acceleration of an object increases with the force acted upon it and decreases with mass. |
| Newton's Third Law of Motion | "Action/Reaction" -- when one object exerts a force on a second, the second object exerts an equal and opposite force back on the first. |
