Space Time Structure
If the position of the particle P changes, the differential change in its position vector r is, in general, given by,
d r = d_{x} i + d_{y} j + d_{z} k (i)The instantaneous velocity and acceleration of P, in Cartesian system therefore are
= v_{x} i + v_{y} j + v_{z} k (ii) = a_{x} i + a_{y} j + a_{z} k (iii)