The motion in which all the particles of a body move through the same distance in the same time is called translatory motion. There are two types of translatory motions: rectilinear motion; curvilinear motion. Since linear motion is a motion in a single dimension, the distance traveled by an object in particular direction is the same as displacement. The SI unit of displacement is the metre. If x 1 is the initial position of an object and x 2 is the final position, then mathematically the displacement is given by: Δ Δ x = x 2 − − x 1