# The potential difference necessary to accelerate an He+ ion ?

The potential difference necessary to accelerate an He+ ion....?

## Homework Statement

"What potential difference is needed to accelerate a He+ ion (charge +e, mass 4u) from rest to a speed of 1.2×10^6 m/s?"

## Homework Equations

K_f + q*V_f = K_i + q*V_i

## The Attempt at a Solution

I figure that:

q = 1.6*10^-19 for the charge of an electron I believe...?

I started off thinking these were somehow true:

V_f = (1/2) m*vf^2

V_i = (1/2) m*vi^2

but now I realize that's just silly, and they both equal K....which is the kinetic energy, sure...but I still have *no* idea what the V's are going to be!

I'm honestly kind of banging my head against the book here...it's not really teaching me what I need to do this problem in any reasonably understandable way. Can anyone help out with this?

gneill
Mentor

What are the units of (electrical) potential difference? Volts, right? But the Volt is a "compound" unit comprising [Joules]/[Coulomb].

So a charge q accelerating though potential difference V will acquire kinetic energy qV:

ΔKE = q*ΔV

You're absolutely right :D Got it, ty!