# Homework Help: Finding velocity given change in potential

1. Nov 19, 2008

### Xender

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

An electron is accelerated from rest by a potential difference of 422 V. What is its velocity?

2. Relevant equations

KE = .5mv^2

3. The attempt at a solution

Since the electron started from rest, there is no KE at the start, just potential. After it is accelerated I assumed that there was not potential and that the electron only had potential energy.
Doing this, i was able to set up a conservation of energy equation where:
422 = .5mv^2

is this the correct way of going about solving this?

2. Nov 19, 2008

### Redbelly98

Staff Emeritus
Your thinking is correct, but you should watch the units carefully. More to the point, what are the energy units that go with 422?

3. Nov 19, 2008

### Xender

eV goes with 422, but KE would be in joules... uh oh! i did some digging and ended up finding that getting the deltaU = q * deltaV (U is change in potential energy, V is change in the potential, q is charge). i multiplied my potential by the charge and then set up the new equation: 6.752E-17 = .5mv^2 and got the right answer. Thanks mate.