How Does a Proton's Velocity Change in a Uniform Electric Field?

[Haniszmi]

Homework Statement

1. A uniform electric field is directed towards the east with a magnitude of 10 N/C. A proton, moving with a speed of 10^5 m /s, enters the field traveling parallel to it. The proton covers a distance of 4 cm while in the field. Find the proton’s final velocity as it leaves the field.

Homework Equations

F=(k)(q1)(q2)/r, F=mv^2/r, Ac=v^2/r

The Attempt at a Solution

I don't understand how to attempt this problem. Confused about the 4cm, not sure if where to use it. How does the proton's velocity change when it enters an electric field?

 

[LowlyPion]

1 Newton / coulomb = 1 volts / meter

And W = q*ΔV

If you know how far it went in the field (.04 m) * 10 v/m that's how much work was exerted on increasing its kinetic energy isn't it since it was || to its direction of motion?