| A | B |
|---|
| speed | distance traveled divided by the time interval during which the motion occurred |
| velocity | quantity describing both speed and direction |
| momentum | a quantity defined as the product of an object's mass and its velocity |
| acceleration | change in velocity divided by the time interval in which the change occured |
| force | the cause of acceleration, or change in an object's velocity |
| balanced forces | forces acting on an object that combine to produce a net force equal to zero |
| unbalanced forces | forces acting on an object that combine to produce a net nonzero force |
| friction | the force between two objects in contact that opposes the motion of either object |
| gravity | the force of attraction between two particles of matter due to their mass |
| inertia | the tendency of an object to remain at reast or in motion with a constant velocity |
| free fall | the motion of a body when only the force of gravity is acting on it |
| terminal velocity | the maximum velocity reached by a falling object that occurs when the resistance of the medium is equal to the force due to gravity |
