A point is space is specified by co-ordinates along each axis. He continued with this approach and created what is known as Coordinate Geometry. Once we can uniquely define where we are, we have to distinguish between distance and displacement . The displacement has the length and direction of the minimum straight-line between the two points. Because displacement has both length and direction, two numbers are needed to describe it.
Distance only needs one number.
Examples of scalars are mass, angle and time. To distinguish between vectors and scalars, textbooks use boldface type for vectors and plainface for scalars. A vector of unit length along the x-axis is written i . A vector of unit length along the y-axis is written j . Adding displacements Displacements add in a different way from familiar quantities like mass, angle and time.