1. Chapter 9 Section 1
Describing Motion

2. Motion
An object is in motion if its distance from another object is changing.
A reference point is a place or object used for comparison to determine if something is in motion.
Common reference points are nonmoving objects example a tree, a building…moving objects can be reference points too such as airplane or train.
An object is in motion if it changes position relative to a reference point.

3. Distance and Displacement
Distance is the length of the path between two points.
Displacement is the length and direction that an object has moved from its starting point.
Distance is the total length of the actual path between two points. Displacement is the length and direction of a straight line between starting and ending points.
A quantity that consists of both a magnitude and a direction is a vector. Displacement is a vector the distance is not.