An object moves in two dimensions according to
\vec{r}(t)=\left(4.0 t^{2}-9.0\right) \hat{i}+(2.0 t-5.0) \hat{j}
where r is in meters and t in seconds. When does the object cross the x-axis?
Answer Choices
A. 0.0 \mathrm{~s}
B. 0.4 \mathrm{~s}
C. 0.6 \mathrm{~s}
D. 1.5 \mathrm{~s}
E. 2.5 \mathrm{~s}