lecture_6_07b

lecture_6_07b - 08/28/08 Physics 13 - Fall 07 - G.R....

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Unformatted text preview: 08/28/08 Physics 13 - Fall 07 - G.R. Goldstein 1 Some Announcements Exam 1 -- Thursday Oct.11 -- In Class closed book, calculators formulas will be provided Homework 2 due Tues. Sept.25 Homework 3 posted on Tues. due Thurs. Oct.4 Practice Exam will be posted in Course Documents 08/28/08 Physics 13 - Fall 07 - G.R. Goldstein 2 Fusion ( see Krane, Ch.12.3 &parts of 13 ) Example - deuteron = d = 2 1 H ~ p and n m d c 2 < m p c 2 + m n c 2 by 2.2 MeV (binding energy) So n + p -> d + 2.2 MeV (extra KE or radiation) Solar energy d + t -> He + n + 17.6 MeV extra energy or 2 1 H + 3 1 H -> 4 2 He + 1 n + Energy (notation ) need cycle at very high temperature to overcome Coulomb repulsion Enhance energy by many N Avogadro H bomb 08/28/08 Physics 13 - Fall 07 - G.R. Goldstein 3 Fission Curve of Binding Energy (add up all n & p masses, subtract mass of nucleus -> B.E.) BE/nucleon around 7.5 to 8.7 MeV for A>20 08/28/08 Physics 13 - Fall 07 - G.R. Goldstein 4 A ~ 50 to 90 is most tightly bound (Fe to Y) 238 U has BE/A ~ 7.7 MeV It is energetically favorable to split into 2 with each fragment at 8.5 MeV Need a trigger - neutron n + 235 U -> X + Y + Energy of other forms Meitner, Hahn, Strassmann (Berlin 1938) Nuclear chain reaction - ~2 ns output (Szilard, Fermi) A-bombs 15 to 20 kilotons (Manhattan Project, Los Alamos) The Nuclear Age! Fission and Binding Energy 08/28/08 Physics 13 - Fall 07 - G.R. Goldstein 5 Gravity and Relativity Equivalence Principle Behavior of objects in Constantly Accelerating frame is indistinguishable from falling objects in G field (feels like...
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lecture_6_07b - 08/28/08 Physics 13 - Fall 07 - G.R....

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