How do I calculate the total energy from an electron-positron collision at .9c?

[cragar]

Homework Statement

Find the total energy produced by an electron positron collision each moving at
.9c , it is a head on collision.

The Attempt at a Solution

Can i just find the relativistic Kinetic energy of one moving at .9c
and then double it and add it to their rest energies and this would be the total energy .
Or do i need to do Lorentz transformations to see what velocity the one particle perceives the other .

 

[Redbelly98]

The Attempt at a Solution

Can i just find the relativistic Kinetic energy of one moving at .9c
and then double it and add it to their rest energies and this would be the total energy.

Yes. It's usually customary to calculate in either the CM or the lab frame, and in this problem they are one and the same.

 

[cragar]

ok thanks for the help