| A | B |
|---|
| inertia | the tendency of all objects to resist any change in motion |
| friction | a force that opposes motion between two surfaces that are touching |
| gravity | a force of attraction between objects that is due to their masses |
| weight | a measure of the gravitational force exerted on an object, usually by the Earth |
| mass | the amount of matter that something is made of |
| acceleration | the rate at which velocity changes; an object accelerates if its speed changes, if its direction changes, or if both its speed and its direction change |
| speed | the rate at which an object moves; speed depends on the distance traveled and the time taken to travel that distance |
| motion | an object's change in position over time when compared with a reference point |
| frame of reference | an object that appears to stay in place in relation to an object being observed for motion |
| velocity | the speed of an object in a particular direction |
| force | a push or a pull; all forces have both size and direction |
