A proton with kinetic energy $1.3384 \times 10^{-14 \, \text{J}$ moving horizontally from north to south, enters a uniform magnetic field $B = 2.0 \, \text{mT}$ directed eastward. Calculate:}
\textbf{(a) the speed of the proton,
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For a charged particle in a magnetic field, use $F = qvB$ to calculate force, $a = F/m$ for acceleration, and $r = \frac{mv}{qB}$ for the radius of the path.