| A | B |
|---|
| motion | The state in which one object's distance from another is changing. |
| reference point | A place or an object used for comparison to determine if an object is in motion. |
| distance | The length of the path between two points. |
| international system of units | A system of measurment based on multiples of ten and on established measures of mass, length, and time. |
| speed | The distance an object travels per unit of time. |
| average speed | The overall rate of speed at which an object moves: calculated by dividing the total distance an object travels by the total time |
| instantaneous speed | The speed of an object at one instant in time. |
| velocity | Speed in a given direction. |
| slope | The steepness of a graph line; the ration of the vertical change (the rise) to the horizontal change (the run) |
| acceleration | The rate at which velocity changes. |
| force | A push or a pull exerted on an object. |
| newton | A unit of measure that equals the force required to accelerate 1 kilogram of mass at 1 meter per second per second. |
| net force | The overall force on an object when all the individual forces acting on it are added together. |
| friction | the force that two surfaces exert on each other when they rub against each other. |
| sliding friction | Friction that occurs when one solid surface slides over another. |
| static friction | Friction that acts between objects that are not moving. |
| fluid friction | Friction that occurs as an object moves through a fluid. |
| rolling friction | Friction that occurs when an object rolls over a surface. |
| gravity | The attractive force between objects; the force that moves objects downhill. |
| mass | The amount of matter in an object. |
| weight | A measure of the force of gravity acting on an object. |
| inertia | The tendancy of an object to resist a change in motion. |
| momentum | The product of an object's mass and velocity. |
| law of conservation of momentum | The rule that in the absence of outside forces the total momentum of objects that interact does not change. |
