| Term | Definition |
|---|---|
| force | a push or pull exerted on an object |
| newton (N) | a unit of measure that equals the force required to accelerate 1 kilogram of mass at 1 meter per second per second |
| net force | the overall force on an object when all the individual forces acting on it are added together |
| unbalanced forces | forces that produce a nonzero net force which changes and object's motion |
| balanced forces | equal forces acting on an object in opposite directions |
| friction | the force that one surface exerts on another when the two surfaces rub against each other |
| static friction | friction that acts on objects that are not moving |
| sliding friction | friction that occurs when one solid surface slides over another |
| rolling friction | friction that occurs when an object rolls over a surface |
| fluid friction | friction that occurs as an object moves through a fluid |
| gravity | the force that pulls objects toward each other |
| mass | the amount of matter in an object |
| weight | the force of gravity on an object at the surface of a planet |
| free fall | the motion of a falling object when the only force acting on it is gravity |
| air resistance | the fluid friction experienced by objects falling through the air |
| terminal velocity | the greatest velocity a falling object can achieve |
| projectile | an object that is thrown |
| inertia | the tendency of an object to resist any change in its motion |
| momentum | the product of an object's mass and velocity |
| law of conservation of momentum | the rule that in the absence of outside forces the total momentum of objects that interact does not change |
| satellite | any object that orbits around another object in space |
| centripetal force | a force that causes an object to move in a circle |
