| A | B |
|---|
| force | a push or a pull |
| newton | SI unit that measures the strength of a force |
| net force | combination of all forces acting on an object at the same time |
| unbalanced forces | forces that have a net force greater than zero; cause acceleration |
| balanced forces | equal but opposite forces acting on an object; net force of zero; no change in motion |
| friction | force that 2 materials exert on each other when they rub against each other |
| static friction | acts on objects that are not moving |
| sliding friction | occurs when one solid slides over another |
| rolling friction | occurs when an objects rolls over a surface |
| fluid friction | occurs as an object moves through a fluid (gas or liquid) |
| gravity | force that pulls objects toward each other |
| mass | measure of the amount of matter in an object |
| weight | measure of the force of gravity on an object |
| free fall | motion of a falling object when the only force acting on it is gravity |
| air resistance | fluid friction experienced by a object falling through air |
| terminal velocity | greatest velocity a falling object reaches |
| projectile | a thrown object |
| inertia | tendency of an object to resist a change in motion |
| momentum | mass times velocity |
| law of conservation of momentum | in the absence of outside forces the total momentum of objects that interact does not change |
| satellite | any object that orbits another object in space |
| centripetal force | any force that causes an object to move in a circular path |
