# Lets Cross The Axis

Classical Mechanics Level 2

An object moves in two dimensions according to

$\vec{r}(t) = (4.0t^2 - 9.0)\vec{i} + (2.0t - 5.0)\vec{j}$

where $$r$$ is in meters and $$t$$ in seconds. When does the object cross the $$x$$-axis?

×