\textbf{184.} A particle with mass $500\,\text{mg}$ enters a uniform magnetic field of $4\,\text{mT}$ perpendicularly at a speed of $10^3\,\dfrac{\text{m}}{\text{s}}$. If the electric charge of the particle is $50\,\mu\text{C}$, what is the acceleration of the particle under the influence of the field, in meters per second squared?
\begin{itemize}
\item[(1)] $0.40$
\item[(2)] $0.04$
\item[(3)] $0.20$
\item[(4)] $0.02$
\end{itemize}