# Proton scattering

proton mass 938MeV/c^2. Consider an elastic collision between two protons. IN the centre of mass frame the kinetic energy of each proton is equal to its rest energy.

calculate the speed of the protons in the CM frame.

clearly they will be equal and opposite velocities so the two speeds should be the same.

E=mc^2
then equate that to relativistic energy momentum relationship $E=\sqrt{c^2p^2+m^2c^4}$ but then i get p=0 so im going wrong somewhere...

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nicksauce
do you mean i should have $c^2p^2=m^2c^4$