1.1. The radius vector of the material point

Consider the motion of a material point M in a rectangular coordinate system, placing the origin of the coorodin at point O on Earth.

The position of point M relative to the reference system can be defined not only by using three Cartesian coordinates but also using one vector quantity - the radius-vector of the point M, drawn to this point from the beginning of the coordinate system (Fig. 1.1). If a - unit vectors (orts) of the axes of a rectangular Cartesian coordinate system, then

(1.1)

Vectors along the corresponding coordinate axes. Projections .