| A | B |
|---|
| reference point | object that appears to stay in place; used to measure distance when measuring motion. |
| speed | distance/time |
| average speed | total distance/total time |
| motion | an object's change in position relative to a reference point |
| velocity | speed of an object in a particular direction |
| force | a push or a pull; all forces have size and direction. |
| Newton | SI unit of force and weight; 100 g = 1 N |
| net force | combination of all the forces acting on an object |
| spring scale/force meter | tool used to measure force and weight |
| balanced forces | when forces on an object create a net force of 0N; no change in motion produced. |
| unbalanced forces | when the net force on an object is not 0N; produce a change in motion. |
| gravity | downward force that gives objects weight; or a force of attraction between objects due to their masses |
| normal force | "reaction" force of an object when an outside force is applied. |
| air resistance | the frictional force of air that can work against motion |
| orbit | circular path of an object (like the moon) constantly "falling" toward another larger object, pulled by its gravitational field |
| centripetal acceleration | acceleration due to the constant change of direction in circular motion |
| mass | amount of matter in an object, measured in grams on a balance |
| weight | amount of gravitational force on on object, measured in Newtons on a spring scale |
| Newton's Law of Universal Gravitation | states that gravity is a universal force that increases with mass and decreases with distance |
