http://physicsforums.com/archive/index.php/t-101357.html
(See Number 1)
Incase the above doesn't make too much sense:
Easiest way is to find the acceleration of the object, then use kinematics to solve for v(final). We know that F = ma = E * q. Notice the units when we divide "q" by "m" = C/kg. So the question is, how can we derive those units from the given?
Since we know the charge density (C/m) and the mass density (kg/m), we can come up with C/kg by (charge density) / (mass density) = C/kg. Therefore, acceleration = 100V/m * (4e-5 / 1e-1 ) ==> 4e-2 m/s^2.
Finally, use the kinematic equation v(f)^2 = v(i)^2 + 2(a)(x). So, v(f) = ( 2 x 4e-2 x 2)^0.5 ==> 0.4 m/s answer.
EDIT: I think.