PHY 251 Fall 2009: homework problem set 3, due PHY 251 drop box in room A-129 by noon on Friday, Sep. 25. 1. A proton with a kinetic energy of 10 GeV collides with an antiproton at rest. They annihilate each other, and produce two identical-energy gamma rays (very energetic photons) that come out at angles θ above and below, respectively, the direction of the proton’s motion. Calculate the energy E and momentum p of the gamma rays, and the angle θ . 2. A atom of the radioactive isotope of carbon 14 C (mass 14 . 003 242 amu, where 1 amu=931.494 MeV/ c 2 ) decays into an electron (mass0 . 000 549 amu) and a singly ionized 14 N atom (mass 14 . 003 074-0. 000 549 amu). If the 14 C atom were at rest, and no other particles were in-volved, calculate the total energy released by this decay, and the energy and momentum of the electron and 14 N atoms after the decay. 3. Do Serway problem 3.6. 4. Look up the overall luminous efficiency of a 100 W incandenscent light bulb on Wikipedia.
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