Question:
Suppose
$\vec{a}$ is a vector of magnitude $4.5$ unit due north. What is the vector
(a) $3 \vec{a}$
(b) $-4 \vec{a}$ ?
Solution:
$a=4.5 \mathbf{n}$, where $\mathbf{n}$ is unit vector in north direction
(a) $3 a=4.5 \times 3 n=13.5$ in north direction
(b) $-4 a=4.5 X-4 n=18$ in south direction