## Find the speed of the charge

For this question, I have solved letters a, b and c. I'm stuck at letter d.

1. The problem statement, all variables and given/known data
Two point charges ql = +2.40 nC and q2 = -6.50 nC are 0.100 m apart. Point A is midway between them; point B is 0.050 m from ql and 0.060 m from q2 (Fig). Take the electric potential to be zero at infinity. Find
(a) The potential at point A;
(b) The potential at point B;
(c) The work done by the electric field on a charge of 2.50 nC that travels from point B to point A.
(d) The speed of the 2.50 nC when it reaches point A, if it starts from rest at point B

2. Relevant equations

KE = 1/2 m v2 ?

3. The attempt at a solution
I have solved a, b and c

a) VA = -737 V
b) VB = -704 V
c) WB->A = +8.2 x 10-8 J

Now I'm stuck at letter D, how do i find the speed? I assume that I might need the equation of KE = 1/2 m v2.. But I dont know how to do it.

What I did was to put +8.2 x 10-8 J as my KE. However, I do not have a mass, so how do I do this?
 Recognitions: Gold Member Homework Help Science Advisor Staff Emeritus Your method is fine. You can't solve this problem without having the mass of the charge.
 Oh you mean that the problem is missing the mass? If that's so then I cannot solve this.