# Homework Help: Find acceleration of an electron

1. Oct 27, 2012

### warnexus

1. The problem statement, all variables and given/known data
An X-ray tube gives electrons constant acceleration over a distance of 20cm . If their final speed is 2.0×107m/s , what are the electrons' acceleration?

2. Relevant equations
v final ^ 2 = v initial ^ 2 + 2a(x-x initial)

3. The attempt at a solution
x = .2 m (after conversion from cm)
v final is given.

how do I find v initial? I need that so I can find acceleration.

2. Oct 27, 2012

### warnexus

apparently the initial velocity is not zero. I heard 99/100 time it is zero from the internet

3. Oct 27, 2012

### frogjg2003

What did you get as your answer with 0 as the initial velocity?

4. Oct 28, 2012

### Redbelly98

Staff Emeritus
You are correct, without knowing v-initial this problem cannot be solved. The problem author problem meant for v-initial to be zero, but that should have been stated or somehow implied in the problem statement. Did you copy the problem exactly as it was given? Or was there an accompanying figure that somehow gave information about the initial velocity?