Given:
Charge of the particle = q
Velocity of projection = u
Electric field intensity = E
Mass of the particle = m
We know that the force experience by a charged particle in an electric field is qE.
Acceleration produced, a = (Negative because the particle is thrown against the electric field)
Let the distance covered by the particle be s.
Then v2 = u2 + 2as
[Here, a = deceleration, v = final velocity]
Here, 0 = u2 − 2as