Distance: Total length of travel, from beginning to end. The distance is always positive.

SI Units: meter, m

Displacement: Displacement, , is the change in position:

SI Units: meter, m

Average Speed:

Average speed is never negative.

SI Units: meters per second, m/s

Average Velocity:

SI Units: meters per second, m/s

Graphical Interpretation of Velocity: In an x-versus-t plot, the average velocity is the slope of a line connecting two points.

Instantaneous Velocity: The velocity at an instant of time is the limit of the average velocity over shorter and shorter intervals.

Graphical Interpretation of Instantaneous Velocity: In an x-versus-t plot, the instantaneous velocity at a given time is equal to the slope of the tangent line at that time.

Constant Velocity: When velocity is constant, the Instantaneous Velocity is equal to the average velocity.

Average Acceleration:

SI Units: meters per second,

Instantaneous Acceleration: Instantaneous Acceleration is the limit of the average limit of the average acceleration as the time interval goes to zero.

Graphical Interpretation of Instantaneous Acceleration: In a v-versus-t plot, the instantaneous acceleration is equal to the slope of the tangent line at a given time.

Constant Acceleration: When acceleration is constant, the instantaneous acceleration is equal to the average acceleration.

Deceleration: An object whose speed is decreasing is said to be