force on charged particle will be F= (const)(q1*q2)/(r^2)

for simplification = q1*q2*const =1 , and also mass of particle will be equal to one .

so acceleration = 1/(r^2)

r is distance between 2 particles, Another simplification is to assume r = X which is displacemnt of chrged particle(assuming fixed particle at fixed cordinates of(0,0,0) .

so equation is accelration=1/(x^2)

where x= velocity*time , velocity = initial velocity + acceleration *time.

so how can i get displacment in variable of time ?

Problem is that X is affected by v , v is affected by a , and a is affected by X. so its a loop.