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Motion
| Term | Definition |
|---|---|
| motion | a change in an object's position relative to a reference point |
| displacement | the distance and direction of an objects change in position (start and stop) |
| speed | the distance an object travels per unit of time |
| velocity | includes speed of an object and the direction of its motion |
| momentum | an object's mass and velocity |
| acceleration | the rate of change of velocity |
| force | a push or pull on an object |
| net force | the sum of all of the forces acting on an object |
| unbalanced force | the net force is not zero on an object |
| balanced force | the net force is zero on an object |
| friction | the force that opposes motion of objects in contact. |
| kinetic friction | the force between two moving objects in contact |
| static friction | the force between two objects in contact that are stationary |
| inertia | the tendency of an object to resist a change in motion |
| gravity | an attractive force between all objects that have mass |
| weight | the gravitational force exerted on an object |
| Newton's First Law of Motion | an object moves at a constant velocity unless an unbalanced force acts on it. |
| Newton's second law of motion | an objects acceleration is in the same direction as the net force on the object and is equal to the net force divided by its mass. |
| Newton's third law of motion | when one object exerts a force on a second object, the second object exerts a force on the first one that is equal in strength and opposite in direction |
| Air resistance | a force that opposes motion of objects that move through the air |
| terminal velocity | the maximum speed an object will reach when falling through a substance such as air. |
| free fall | when gravity is the only force acting on an object |
| Law of conservation of momentum | if no external forces act on a group of objects, their total momentum does not change. |