Everything in motion is determined by a starting point.The starting point is relatve in all math.All the atom in an object move at the same speed when in motion.
We measure distance by definite intervals away from a starting point.If an object moving from point (A) has to move to a point (B) (10 metres away)then we measure the velocity by observing the time spent for the object to move through an interval of measurement (say a metre).If the object takes 5 seconds to move from starting point (A) to the one meter interval, we say it moves 1m/second.If there is nothing to slow it down it will move 10 metres in 50 seconds or v=10m/s.
To measure its acceleration we have to see if the interval of time from two definite intervals has increased.Say the object moved from interval 7 to interval 8 in 4.99 seconds.We say it is accelrating 0.01 metres per second or a=0.01m/s.
At least I think thats right.