From Mechanics

We have \displaystyle \mathbf{a}=4\mathbf{i}– 8\mathbf{j},\ \ \displaystyle \mathbf{u}=4\mathbf{i}– 8\mathbf{j}\ \ and \displaystyle \ \ \mathbf{ r}_{0}=6\mathbf{i}+2\mathbf{j}.

The most suitable equation to use is \displaystyle \mathbf{v}=\mathbf{u}+\mathbf{a}t\ \.

Substituting the above values gives a vector eqaution for \displaystyle t.

\displaystyle 4\textrm{.}8\mathbf{i}-6\textrm{.}8\mathbf{j}=4\mathbf{i}– 8\mathbf{j}+(4\mathbf{i}– 8\mathbf{j})t\ \