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frame of reference

a system of objects that are not moving with respect to one another

relative motion

movement in relation to a frame of reference

distance

the length of the path between two points

vector

a quantity that has magnitude and direction

resultant vector

the vector sum of two or more vectors

speed

the ratio of the distance an object moves to the amount of time the object moves

average speed

the total distance traveled divided by the time it takes to travel that distance

instantaneous speed

the rate of which an object is moving at a given moment in time

velocity

the speed and direction in which an object is moving

acceleration

the rate at which velocity changes

free fall

the movement of an object towards Earth solely because of gravity

constant acceleration

a steady change in velocity

linear graph

the displayed data form straight-line parts

nonlinear graph

a curve connects the data points that are plotted