| A | B |
|---|
| terminal velocity | the constant velocity of a falling object when the size of the upward force of air resistance matches the size of the downward force of gravity |
| free fall | the condition an object is in when gravity is the only force acting on it |
| projectile motion | the curved path an object follows when thrown or propelled near the surface of the Earth |
| inertia | the tendency of all objects to resist any change in motion |
| momentum | a property of a moving object that depends on the object's mass and velocity |
| friction | a force that opposes motion between two surfaces that are touching |
| gravity | a force of attraction between objects that is due to their masses |
| weight | a measure of the gravitational force exerted on an object, usually by the Earth |
| mass | the amount of matter that something is made of |
| acceleration | the rate at which velocity changes; an object accelerates if its speed changes, if its direction changes, or if both its speed and its direction change |
| speed | the rate at which an object moves; speed depends on the distance traveled and the time taken to travel that distance |
| velocity | the speed of an object in a particular direction |
| force | a push or a pull; all forces have both size and direction |
| Law of Conservation of Momentum | when objects collide, the total amount of momentum stays the same |
