A position vector is a fixed vector that locates the position of a point in space relative to another point. Consider a screw eye fixed to a wall and a cable OP attached to it. Establish a cartesian coordinate system with screw eye at the origin and the component vectors along the axes to locate point P on the cable. A position vector r directed from the origin to point P can be expressed in the cartesian vector form. For a general representation of a cartesian vector, consider a bracket fixed on a wall and a cord attached to it. Let nA and nB be the position vectors extending from the origin to points A and B. So the resultant position vector n from point A to B, can be obtained using the triangle rule and by expressing nA and nB in the cartesian vector form. i, j, and k are the unit vectors along the components of the position vector n formed by subtracting the coordinates of A from B.