<<Units`
a=0.1 Second^(-1)
b=10^(-4) Second^(-2)

v[t_]:={2 a t Second, -1, (b t^2 Second^2)/2} Meter/Second

r0={-6,0,2} Meter
r[t_]:=r0+Integrate[v[ti],{ti,0,t}]Second

ParametricPlot3D[r[t]/Meter,{t,0,20},PlotRange->{{-20,20},{-20,20},{-20,20}}]
