Kinematics is the study of motion of bodies without considering the cause of the motion i.e., forces. Newtonian mechanics are valid for primary inertial system or astronomical frame of reference. The primary inertial frame of reference is an imaginary set of rectangular axes assumed to have no translation or rotation in space. Space is the geometric region occupied by bodies. The position in space is described with reference to these rectangular axes. We can describe the motion of a particle in (i)· x, y, z (ii) r, e, z and (iii) R, θ, ϕ coordinates. x, y, z coordinates are called rectangular coordinates or cartesian coordinates. r, θ, z is cylindrical coordinates, and R, θ, ϕ is spherical coordinates.
The motion of P can also be described by measurements along the tangent t and normal n to the path at point P. The direction of n lies in the local plane which also contains A, P, B points. This local plane is also called osculating plane (Refer Fig. 1.1).