lecture_6_07b

lecture_6_07b - Physics 13 Fall 07 G.R Goldstein 1 Some...

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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 n’s 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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This note was uploaded on 03/27/2008 for the course PHY 13 taught by Professor Garyr.goldstein during the Fall '04 term at Tufts.

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lecture_6_07b - Physics 13 Fall 07 G.R Goldstein 1 Some...

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