At 8 seconds the problem has been reduced to a linear equation. $X_1 = X + Vt + {1 \over 2} a t^2$ where $X = 1.9m, V = 1.7 {m \over s}, a = 0 {m \over s^2}$ Then this equation becomes... $X(t) = 1.9 + 1.7t$ Before the 8 second mark none of them seem to be linear or parabolic. This is just speculation though. I believe this because it seems that the velocity and acceleration are irregular functions of time, the functions wouldn't fit a linear curve or the perfect definition of a parabolic conic section. With out the explicit functions I couldn't know for sure whether this is the case though