| A | B |
| gravity | the force of attraction between masses that is due to their masses |
| motion | an objects change in position realative to a reference point |
| acceleration | the rate at which velocity changes over time |
| velocity | the speed of an object in a particular direction |
| air resistance | the force that opposes teh motion of objects through air |
| terminal velocity | the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity |
| free fall | the motion of a body when only the force of gravity is acting on the body |
| orbiting | when one object travels arounf another object in space |
| centripetal force | the unbalanced force that causes objects to move in a circular path |
| projectile motion | the curved path that an object follows when thrown, launched, or otherwise projected near the Earth's surface |
| horizontal motion | the force that makes an object move forward |
| vertical motion | motion that is perpendicular to the ground |