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Unformatted text preview: Announcements For the lab this week, you will have 2 lab session to complete it. They will be collected after week 1 and redistributed the following week. Pick up HW assignments: Due next Wednesday. Read page 713 in Schwarz. Do exercises 16. In http://particleadventure.org/particleadventure/frameless/startstandard.html read through the Section Particle Decays and Annihilations Slides ah (see slide key on Course Assignments Web page) Conservation Laws Conservation Laws Conservation laws in Physics can give explanations as to why some things occur and other do not. Three very important Conservation Laws are: I. Conservation of Energy II. Conservation of Momentum III. Conservation of Charge Energy Conservation (I) There are many forms of energy. For now, well focus on two types 1. Kinetic Energy (KE) Energy of motion KE = mv 2 if v is much less than c (v << c ) 2. Mass Energy E = m c 2 E = m c 2 m = mass c = speed of light = 3x10 8 [m/sec] That is, mass is a form of energy , and the conversion is to just multiply the mass by a constant number (the speed of light squared)! Conservation of Energy (II) A B v A v B Total Energy (after decay) = E A + E B = (KE A +m A c 2 ) + (KE B +m B c 2 ) Suppose D decays into 2 particles A and B , what is the energy of the system afterward? D Total Energy (initially) = E D = m D c 2 Since energy must be conserved in the decay process, m D c 2 = (KE A +m A c 2 ) + (KE B +m B c 2 ) Conservation of Energy (III) m D c 2 = (KE A +m A c 2 ) + (KE B +m B c 2 ) m D c 2 = (KE A +m A c 2 ) + (KE B +m B c 2 ) Important points here: 1) This equation DOES NOT say that kinetic energy is conserved 2) This equation DOES NOT say that mass is conserved 3) This equation states that the total energy is conserved Total energy before decay = Total energy after decay Important points here:...
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 Spring '09

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