Answer
$\sqrt{\frac{k{{Q}_{1}}{{Q}_{2}}}{N}}$.
Work Step by Step
$N=\frac{k{{Q}_{1}}{{Q}_{2}}}{{{s}^{2}}}$
Multiply $\left( {{s}^{2}} \right)$ on both sides of the equation.
$\begin{align}
& N\times {{s}^{2}}=\frac{k{{Q}_{1}}{{Q}_{2}}}{{{s}^{2}}}\times {{s}^{2}} \\
& N{{s}^{2}}=k{{Q}_{1}}{{Q}_{2}}
\end{align}$
Then, divide by $N$ on both sides of the equation,
$\begin{align}
& N{{s}^{2}}=k{{Q}_{1}}{{Q}_{2}} \\
& \frac{N{{s}^{2}}}{N}=\frac{k{{Q}_{1}}{{Q}_{2}}}{N} \\
& {{s}^{2}}=\frac{k{{Q}_{1}}{{Q}_{2}}}{N}
\end{align}$
Taking square roots on both sides of the equation,
$\begin{align}
& \sqrt{{{s}^{2}}}=\sqrt{\frac{k{{Q}_{1}}{{Q}_{2}}}{N}} \\
& s=\sqrt{\frac{k{{Q}_{1}}{{Q}_{2}}}{N}}
\end{align}$
Thus, the value is $s=\sqrt{\frac{k{{Q}_{1}}{{Q}_{2}}}{N}}$.
