| A | B |
|---|
| force | A push or pull exerted on an object. |
| newton | 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 an 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. |
| 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. |
| 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. |
