Answer:
To describe motion accurately and completely, a frame of reference is necessary. frame of reference ( or reference frame) consists of an abstract coordinate system and the set of physical reference points that uniquely fix ( locate and orient ) the coordinate system and standardize measurements within that frame.
Step-by-step explanation:
The different observations occur because the two observers are in different frames of reference. A frame of reference is a set of coordinates that can be used to determine positions and velocities of objects in that frame; different frames of reference move relative to one another.