Calculating Speed of Electron after 50keV Work

[Brown Arrow]

Homework Statement

what is the speed of en electro, initially at rest,if a total work of 50keV is done on it?
1eV=1.6*10^-19j m_e=9.11*10^-31kg

Homework Equations

relastic energy equaltion.

The Attempt at a Solution

i converted the total work to total energy

E_total=8*10^-15

then i set E_total=(mc²)/(1-(v/c)²)^1/2
when i try solving it i keep getting sqrt of a negative #
could someone tell me where I am going wrong

 

[zhermes]

You have to include the rest mass as part of the total energy, not just the work done on the particle

 

[Brown Arrow]

oh i see thanks!
let me see if it works

 

[Brown Arrow]

yeah it works thanks again !