Answer
See below:
Work Step by Step
The magnitude of the linear combination of the vector is calculated from,
$\left\| \mathbf{v} \right\|=\sqrt{{{a}^{2}}+{{b}^{2}}}$
Where, a is the horizontal component of $\mathbf{v}$ and b is the vertical component of $\mathbf{v}$.
$\begin{align}
& \left\| \mathbf{v} \right\|=\sqrt{{{0}^{2}}+{{(-5)}^{2}}} \\
& =\sqrt{0+25} \\
& =\sqrt{25} \\
& =5
\end{align}$
Thus, the magnitude of the vector is $5$.
