### average speed

how fast an object is moving, is the absolute value of the slope of an object's position-time graph

### average velocity

the change in position, divided by the time during which the change occured, is the slope of an object's position-time graph

### coordinate system

a system used to describe motion that gives the zero point location of the variable being studied and the direction in which the values of the variable increase

### displacement

a change in position having both magnitude and direction; is equal to the final position minus the initial position

### instantaneous velocity

a measure of motion that tells the speed and direction of an object at a specific instant in time

### motion diagram

a series of images showing the positions of a moving object taken at regular (equal) time intervals

### particle model

a simplified version of a motion diagram in which the moving object is replaced by a series of single points

### position vs. time graph

a graph that can be used to determine an object's velocity and position, as well as where and when two objects meet, by plotting the time data on a horrizontal axis and the position data on a vertical axis

### slope of a position vs. time graph

indicates both the magnitude and direction, indicates the average velocity of the object and not its speed