| A | B |
|---|
| average speed | rate of motion calculated by dividing the distance traveled by the amount of time it takes to travel that distance |
| instantaneous speed | speed of an object at any given time |
| velocity | speed of an object and its direction of motion; changes when speed changes, direction of motion changes, or both change |
| acceleration | change in velocity divided by the amount of time needed for the change to occur; takes place when an object speeds up, slows down, or changes direction |
| force | a push or a pull; SI unit is the newton |
| friction | force that resists motion between two touching surfaces and always acts opposite to the direction of motion |
| inertia | tendency to resist a change in motion |
| work | done when an applied force causes an object to move in the direction of the force |
| simple machine | device that makes work easier with only one movement; can change the size or direction of a force, and includes the wedge, screw, lever, wheel and axle, pulley, and inclined plane |
| compound machine | a combination of simple machines |
| mechanical advantage | number of times a machine multiplies the effort force you apply to it |
| pulley | an object with a groove, like a wheel, with a rope or chain running through the groove |
| lever | a rod or plank that pivots about a fixed point |
| inclined plane | a sloped surface |
