Particle in 3-D

A particle moves in a $3$ -dimensional space so that its acceleration vector at any time $t>0$ is $\boldsymbol{a}(t) = \boldsymbol{i} + 2\ \boldsymbol{j}$ and its initial velocity is $\boldsymbol{v}(0) = \boldsymbol{k}$ . If $S$ is the speed of the particle at $t = 2$ , what is the value of $S^2$ ?