From Mechanics

\displaystyle \mathbf{a}=\frac{d\mathbf{v}}{dt}=6\mathbf{j}\ \text{m}{{\text{s}}^{-2}}

This is a constant vector with magnitude \displaystyle 6\ \text{m}{{\text{s}}^{-2}} and points vertically upwards (\displaystyle \mathbf{j} direction).