The potential difference necessary to accelerate an He+ ion ?

  • #1
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?
 

Answers and Replies

  • #2
gneill
Mentor
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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
 
  • #3


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

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