E= k|q|/d^2

The question is: the d, is it the distance from where it starts to where it stops? I ask this because I am aslo given that the acceleration is 4.5m in the first 3 micro-seconds. SO should I divide 3micro-s by 4.5 to find what the d is after 1 s?

Or did I get all this wrong?

Another thing: Can I use the definition of electric field and use : a = F/m or

a = eE/m ??? since I know the charge and the mass and the acceleration???

THanks