What is the speed at a great distance from the alpha particle

[abm77]

Homework Statement

An alpha particle has a charge of 2e and is fixed at the origin. A proton is located 2.00x10^-8 m from the alpha particle along the x-axis. When the proton is released, what is its speed at a great distance from the alpha particle

q = 2e
r = 2.00x10^-8
v = ?

Homework Equations

ɛ = kq / r
ɛ = ΔV / r
ΔE = qΔV
E = kq1q2 / r

The Attempt at a Solution

I have no idea how to start this one. As every way I can think of doing it results in missing information that is needed to solve for v. For example when I tried to solve for ɛ and then use it to solve for ΔV, and use that to solve for ΔE, I get stuck with E_E = E_K but no mass to solve for v.

 

[abm77]

Fixed formatting problem

 

[haruspex]

What is the PE of the system initially? What is its final PE? Also consider momentum.