Velocity and momemtum of 10 Mev Electron

[madjens]

Homework Statement

Find the velocit y and momentum of an electron (rest mass of 0.511MeV) with a
kinet ic energy of 10.0 MeV.

The Attempt at a Solution

The momentum I calculate using sqrt(2KEm) is giving me a V larger than the speed of light. This can't be true.

If I try
Rest E + KE = sqrt (m2c4 - p2c2) it gives me a negative root.

 

[madjens]

Nevermind, I figured it out.