NEET Physics Vectors MCQ Question

The acceleration vector $\mathbf{a}(t)$ is the second derivative of the position vector $\mathbf{r}(t)$. Differentiating twice, we get $\mathbf{a}(t) = 0 \hat{i} + 0.4 \hat{j} + 0 \hat{k}$, with magnitude $\sqrt{0^2 + 0.4^2 + 0^2} = 0.4 \text{ m/s}^2$.