Ok so, both, the particle and the sheet, are positively charged therefore the electric forces are repulsive. So on the particle it's weight is mg(down) and the electric force on it is qE(up)!
But does this allow us to switch to a negative sign while working with Energies?
Hey I understood the gravity was missing. But I still don't get how you arrived to this formula from the energy conservation. a and b refer to the initial and final positions.
If Ka+Uag+Uael=Kb+Ubg+Ubel and Ka=0 (at rest) and Ug=mgh and Uel=qEh
Then mgha + qEha = 0.5mv^2 + mghb + qEhb
Then v^2 =...