When the velocity is parallel to the acceleration, the motion is one dimensional. If in addition the acceleration is constant, simple formulas describe the motion:
In the equations, a is the acceleration, v is velocity, and x is position. To apply these equations, the usual choices must be made for the location of the origin and the plus direction. In addition, an "origin" for time must be chosen. Typically it is when the motion was first observed. That initial time is taken to be t=0, as if the observations were being timed with a stopwatch.
In the equations, v(sub 0) is the initial velocity and x(sub 0) is the initial position.