ABSTRACT
Chapter 4 taught us some basic knowledge of motion along a straight line. This chapter generalizes the concept of motion and introduces some fundamental quantities necessary for its description.
What is motion? Vaguely speaking, it is the change in the state of an object. More precisely, it is the change in the position of an object with time. Still more precisely, we must speak of the motion of an object relative to an observer, although the “object” could be a person, and the “observer” a thing.
