# Homework Help: Minium Electric Potential

1. Aug 3, 2010

### coreluccio

1. The problem statement, all variables and given/known data

A plutonium-239 nucleus, initially at rest, undergoes alpha decay to produce a uranium-235 nucleus. The uranium-235 nucleus has a mass of 3.90 * 10-25 kg, and moves away from the location of the decay with a speed of 2.62 * 105 m/s.

Determine the minimum electric potential difference that is required to bring the alpha particle to rest.

2. Relevant equations

3. The attempt at a solution

mu-235 = 3.90 * 10-25 kg
vu-235 = 2.62 * 105 m/s
map = 6.65 * 10-27 kg
qap = +2e = +2(1.60 * 10-19 C) = +3.20 * 10-19 C

|pu-235| = |pap|
mu-235vu-235 = mapvap
vap = mu-235vu-235/map
vap = (3.90 * 10-25 kg)(2.62 * 105 m/s)/(6.65 * 10-27 kg)
vap = 1.536541353 * 107 m/s
Ek = 1/2mapvap2
Ek = 1/2(6.65 * 10-27 kg)(1.536541353 * 107 m/s)2
Ek = 7.85018977 * 10-13 J
Ek = qapVstop
Vstop = Ek/qap
Vstop = (7.85018977 * 10-13 J)/(3.20 * 10-19 C)
Vstop = 2.45 * 106 V

The minimum electric potential difference that is required to bring the alpha particle to rest is 2.45 * 106 V.

Last edited: Aug 3, 2010
2. Aug 3, 2010

### coreluccio

I posted my work/answer. I just want to confirm that it is in fact right.

3. Aug 3, 2010

### diazona

You're not being ignored, sometimes it just takes a while ;-) Anyway, the procedure you used looks reasonable, and I don't see any obvious errors in what you've done.