| A | B |
|---|
| Name | Definition |
| force | an influence tending to change the motion of an object or produce motion in a stationary object |
| contact force | a force that is exerted only when two objects are touching |
| noncontact force | a force that one object exerts on another when they are not touching |
| net force | combination of all the forces acting on an object |
| unbalanced force | forces that combine to form a net force that is not zero |
| balanced force | forces that combine to form a net force that is zero |
| Newton’s first law of motion | if the net force on an object is zero, an object at rest remains at rest, or, if the object is moving, it continues to move in a straight line with constant speed |
| vector | a quantity with both size and direction |
| gravity | an attractive force that exists between all objects that have mass |
| law of universal gravitation | all objects are attracted to each other with a force that depends on the masses of the objects and the distance between them |
| weight | the gravitational force exerted on an object |
| friction | a force that opposes the movement between two surfaces in contact |
| elastic force | the force exerted by a material when it is stretched or compressed |
| tension force | a pulling force applied to an object that can make the object stretch |
| compression force | a squeezing force applied to an object that can make an object shrink |
| normal force | a force exerted by an object that is perpendicular to the surface of the object |
| velocity | the speed and direction in which an object is traveling |
| centripetal force | in circular motion a force that acts perpendicular to the direction of motion toward the center of the circle |
| Newton’s second law of motion | acceleration of an object equals the net force divided by the objects mass |
| Newton’s third law of motion | when one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object |
| acceleration | the rate of change of velocity with time |
