| A | B |
|---|
| acceleration | rate of change in velocity |
| force | push or pull that gives energy to an object |
| friction | force that acts in the opposite direction of motion |
| gravity | responsible for accelerating an object toward the Earth |
| inertia | property of matter that tends to resist any change in motion |
| law of universal gravitation | states that all objects in the universe attract each other by the force of gravity |
| momentum | mass of an object times its velocity |
| motion | change in position in a certain amount of time |
| newton | unit of force |
| speed | rate at which an object moves |
| velocity | rate at which an object moves in a given direction |
| law of conservation of momentum | the total momentum of any group of objects remains the same unless outside forces act on the objects |
| frame of reference | object that is assumed to be stationary and is used for comparison when motion is described |
| balanced forces | forces that are in opposite directions and are equal in size; no change in motion occurs |
| unbalanced forces | forces that are acting in the same direction that change the motion of an object |
| Newton's first law of motion | an object at rest tends to stay at rest; an object in motion tends to stay in motion unless acted upon by an unbalanced force |
| Newton's second law of motion | force = mass times acceleration |
| Newton's third law of motion | for every action, there is an equal and opposite reaction |
| weight | a measure of the force of gravity on an object |
