| A | B |
|---|
| force | a push or a pull |
| gravity | the force of attraction that exists between any two objects |
| mass | the amount of matter in an object |
| weight | a measure of the pull of gravity on an object's mass |
| newton | in the metric system, the unit used to measure force or weight |
| net force | the combination of all the forces acting on an object |
| balanced forces | equal forces acting in opposite directions |
| relative motion | the change in position of one object compared to the position of another |
| frame of reference | the object an observer uses to detect motion |
| speed | the distance an object moves in a certain period of time |
| instantaneous speed | the speed at any given point |
| speedometer | a device that shows instantaneous speed |
| velocity | a measure of both the speed and direction of a moving object |
| acceleration | the change in velocity during a particular time period |
| law | a statement that describes events or relationships that exit in nature |
| inertia | the resistance of an object to change in its state of motion |
| friction | a force between surfaces that resists the movement of one surface past the other surface |
| air resistance | the friction from air molecules hitting an object as the object moves through the air |
| Newton's First Law of Motion | All objects resist changes in motion. |
| Newton's Second Law of Motion | An object's acceleration depends on the mass of the object and the size and direction of the force acting on it. |
| Newton's Third Law of Motion | When one object exerts a force upon a second object, the second object exerts an equal and opposite force upon the first object. |
