Relativistic Energy/Momentum of Particles

[div4200]

Homework Statement

A particle with mass M at rest decays into two particles, one with mass m1, and the other with mass m2. Use conservation of energy and momentum to show that:

E1 = (M^2 + m1^2 - m2^2)(c^2)
________________________
2M

Homework Equations

p = mv / sqrt(1-v^2/c^2)
E = mc^2 / sqrt(1-v^2/c^2)
E = sqrt(p^2*c^2 + m^2*c^4)

The Attempt at a Solution

I think that it has something to do with 4-vectors, but I'm not sure. Thanks in advance!

 

[fzero]

Can you write down the equations for conservation of energy and momentum? Note that it will be much simpler if you write things in terms of the momentum instead of the velocities.