Answer
$v=2.65\times 10^{6} m/s$
Work Step by Step
By the conservation of energy;
Loss in energy = Gain in energy
Thus;
$q\Delta V=\frac{1}{2}mv^{2}$
$v=[\frac{2q\Delta V}{m}]^{1/2}$ [ Since, $\Delta V= Ed$]
$v=[\frac{2\times 1.6\times 10^{-19}\times 2 \times 10 ^{4}\times 10 ^{-3}}{9.11 \times 10^{-31} }]^{1/2}$
$v=2.65\times 10^{6} m/s$
