1. The problem statement, all variables and given/known data The neutral pion is an unstable particle that decays very quickly after its creation into two photons (“particles” of light: v = c, mo = 0). The pion has a rest-mass energy of 135 MeV. Consider a pion that has a kinetic energy of 90 MeV 1) Determine the v of this pion 2) Determine the momentum of the pion 3) Determine the sum of the energies of the photons 2. Relevant equations 1) moc2[tex]\gamma[/tex] = KE + Rest E 2) mov[tex]\gamma[/tex] = p 3) Ephotons= pc 3. The attempt at a solution I'm pretty sure I got 1 and 2. For 1 I added the KE + RE, converted to proper units, and finally got v = .80c For 2 I got p = 9.6 x 10-20 kg m/s Now I'm not so sure about #3. I think Ephotons = pc because momentum is conserved, and all of the pion's momentum gets turned into the photons' momentum. However, what about adding up the original rest mass energy + KE of the pion? If I do that I get a bigger energy then if I do pc. Thanks for all the help!