179. Four charged particles are placed at the corners of a square with side $20\,\text{cm}$ as shown in the figure below. If the net electric force on $q_2$ in SI units is $\vec{F} = -9\hat{i}$, how many microcoulombs is $q_2$? $$\left(k = 9\times10^9\,\frac{\text{N}\cdot\text{m}^2}{\text{C}^2}\right)$$ [Figure: Square with charges at corners: $q_1 = 4\,\mu\text{C}$ (top left), $q_2 = -4\,\mu\text{C}$ (top right), $q_3$ (bottom left), $q_4 = -4\,\mu\text{C}$ (bottom right), with coordinate axes $x$ and $y$ shown]
[(1)] $-8\sqrt{2}$
[(2)] $-4$
[(3)] $4$
[(4)] $8\sqrt{2}$
\textbf{179.} Four charged particles are placed at the corners of a square with side $20\,\text{cm}$ as shown in the figure below. If the net electric force on $q_2$ in SI units is $\vec{F} = -9\hat{i}$, how many microcoulombs is $q_2$?
$$\left(k = 9\times10^9\,\frac{\text{N}\cdot\text{m}^2}{\text{C}^2}\right)$$
\textit{[Figure: Square with charges at corners: $q_1 = 4\,\mu\text{C}$ (top left), $q_2 = -4\,\mu\text{C}$ (top right), $q_3$ (bottom left), $q_4 = -4\,\mu\text{C}$ (bottom right), with coordinate axes $x$ and $y$ shown]}
\begin{itemize}
\item[(1)] $-8\sqrt{2}$
\item[(2)] $-4$
\item[(3)] $4$
\item[(4)] $8\sqrt{2}$
\end{itemize}