# Particles and special relativity

hi wondering if i could get a little help with this question

A particle with rest mass m has kinetic energy equal to twice its rest energy. The particle decays into 2 photons which emerge in opposite directions, one travelling in the same direction as the particle before its decay. Find expressions, in terms of m for:

(a) the momentum of the particle
(b) the energy of each of the 2 photons

thanks for any help.

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HallsofIvy
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What help do you want? Where is the difficulty? In other words, what have you done on this yourself?

Meir Achuz
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da_warped_1 said:
hi wondering if i could get a little help with this question

A particle with rest mass m has kinetic energy equal to twice its rest energy. The particle decays into 2 photons which emerge in opposite directions, one travelling in the same direction as the particle before its decay. Find expressions, in terms of m for:

(a) the momentum of the particle
(b) the energy of each of the 2 photons

thanks for any help.
For (a), start with T=E-m=2m. Solve for E and then for p.
For (b), LT each photon's energy in the particle's rest frame (k=m/2),
to the frame moving with velocity v=p/E.