Magnetism and Magnetic Fields- Determining mass of ion

[alyssadlt85]

Homework Statement

An ion of mass m and charge q is accelerated from rest through a voltage of ΔV. It then enters a magnetic field. Determine the mass of the ion in terms of the measurable quantities: q, ΔV, (B^→) , and x.

Homework Equations

The Attempt at a Solution

m = q(B^2)(x^2)/(8ΔV)
this is where i am:

F=ma
F - qV x B
ma =qVB

Ui+Ki=Uf+Kf
Ui=Uf+Kf
Ui-Uf=1/2mv^2
ΔU= 1/2mv^2
ΔVq= 1/2 mv^2

 

[rude man]

what is x?
what does "B^→" mean?