If a particle is located at p1,with coordinate x1, at time t1 and moves so that it occupies a difference position P2 at a later time t2,with coordinate x2 , then the average velocity vav of the particle over that time period is defined as the relative displacement vector (x2-x1), divided by the time elapsed, t2-t1
vav= (x2-x1)/(t2-t1)
Next: 2.3 Instantaneous Velocity