Compton Effect: Finding Final KE of Electron

[stinger302]

Homework Statement

In the compton effect a .150nm photon strikes a free staionary electron in a head-on elastic collision and knocks it into the foward direction. The rebounding photon recoils directly backwards. Use the collision conservation laws to find the final kinetic energy of the electron

Homework Equations

P = h/lambda
Ek = 1/2mv^2

The Attempt at a Solution

All i know is i need the momentum of the photon which is p =h/lambda = 4.42e-24 kg m/s basically i just need to know how to find the speed of the elctron which i can sub into ek = 1/2mv^2

 

[adriansd]

would it not be c?

 

[stinger302]

is it, i didn't think that electrons could travel at c