1.6 Motion in One Dimension

An object’s motion can be described in terms of three fundamental quantities: its position $\vec{r}$, velocity $\vec{v}$, and acceleration $\vec{a}$. These are vectors, but for motion in one dimension, the vectors are restricted to point only “forward” or “backward.” Consequently, we can describe one-dimensional motion with the simpler quantities x, $v_x$, and $a_x$ (or y, $v_y$, and $a_y$). However, we need to give each of these quantities an explicit sign, positive or negative, to indicate whether the position, velocity, or acceleration vector points forward or backward.