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Unformatted text preview: 1 Wed. Oct 20 Phy107 Lecture 19 Hour Exam 2 : Wednesday, Oct. 27 Inclass (1300 Sterling Hall) Twenty multiplechoice questions Will cover: 8.18.6 (Light and E&amp;M) 9.19.5 (E&amp;M waves and color) 10, 11 (Relativity) You should bring Your student ID 1 page notes, written double sided Calculator Pencil for marking answer sheet HW#7: Chapter 11 Concept: 2, 6,14, 20, 32, 34 Problems: 4, 6 Wed. Oct 20 Phy107 Lecture 19 From Last Time World line : path of particle through spacetime. World line is made up of sequence of events, plotted as points in spacetime. Different inertial reference frames represented as tilted coordinate axes on spacetime diagram. Event has different coordinates (space &amp; time) measured on these coordinate axes. But the combination x 2 c 2 t 2 is universal in that it is measured to be the same for all observers. Suggests that space &amp; time are components of space time, a conceptually new quantity. Wed. Oct 20 Phy107 Lecture 19 Today: Forces, Work, and Energy in Relativity or, What about Newtons laws? Relativity dramatically altered our perspective. But clearly objects still move, spaceships are accelerated by thrust, work is done, energy is converted. All the things we studied in the first six weeks. But some things are different in relativity. Wed. Oct 20 Phy107 Lecture 19 As motorcycle velocity approaches c , V ball also gets closer and closer to c End result: nothing exceeds the speed of light. V ball = v ball + v motorcyle 1 + v ball v motorcycle c 2 v motorcycle Observes ball to have velocity V ball =0.96c motorcycle v ball ball Wed. Oct 20 Phy107 Lecture 19 Newton again Fundamental relations of Newtonian physics acceleration = Force / mass acceleration = (change in velocity)/(change in time) Work = Force x distance Kinetic Energy = (1/2) (mass ) x ( velocity ) 2 Change in Kinetic Energy = net work done Newton predicts that a constant force gives Constant acceleration Velocity proportional to time Kinetic energy proportional to (velocity) 2 Wed. Oct 20 Phy107 Lecture 19 Momentum Newtons laws become simpler when we use the momentum of a particle....
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 Spring '08
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