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Unformatted text preview: Page 1 Physics 207 Lecture 2 Physics 207: Lecture 3, Pg 1 Physics 207, Physics 207, Sept. 12, The inclined plane and unit conversion Sept. 12, The inclined plane and unit conversion Flight 173 ran out of fuel in flight. So: "How does a jet run out of fuel at 26,000 feet?" 1. A maintenance worker found that the fuel gauge did not work on ground inspection. He incorrectly assured the pilot that the plane was certified to fly without a functioning fuel gauge if the crew checked the fuel tank levels. 2. Crew members measured the 2 fuel tank levels at 62 cm and 64 cm. This corresponded to 3758 L and 3924 L for a total of 7682 L according to the plane's manual. 3. The ground crew knew that the flight required 22,300 kg of fuel. The problem they faced was with 7,682 L of fuel on the plane, how many more liters were needed to total 22,300 kg of fuel? 4. One crew member informed the other that the "conversion factor" (being the fuel density) was 1.77. THE CRUCIAL FAULT BEING THAT NO ONE EVER INQUIRED ABOUT THE UNITS OF THE CONVERSION FACTOR. So it was calculated that the plane needed an additional 4,917 L of fuel for the flight. Alas that was too little. Physics 207: Lecture 3, Pg 2 Physics 207, Physics 207, Lecture 3, Sept. 12 Lecture 3, Sept. 12 Agenda Agenda Assignment: Assignment: 1. 1. For Monday read Chapter 4 For Monday read Chapter 4 2. 2. Homework Set 2 due Wednesday of next week (start ASAP) Homework Set 2 due Wednesday of next week (start ASAP) c Finish Chapters 2 & 3 Finish Chapters 2 & 3 x One One-Dimensional Motion with Constant Acceleration Dimensional Motion with Constant Acceleration x Free Free-fall and Motion on an Incline fall and Motion on an Incline x Coordinate systems Coordinate systems Physics 207: Lecture 3, Pg 3 Recall Recall in one in one-dimension dimension c If the position x is known as a function of time, then we can deduce the velocity v ) ( ) ( 1 t v dt x x t t =- dt dx v = ) ( t x x = v t x t Area under v curve [Assumes x(0) =0] Slope of x(t) curve Physics 207: Lecture 3, Pg 4 Representative examples of speed Representative examples of speed Speed ( Speed ( m/s m/s ) Speed of light 3x10 8 Electrons in a TV tube 10 7 Comets 10 6 Planet orbital speeds 10 5 Satellite orbital speeds 10 4 Mach 3 10 3 Car 10 1 Walking 1 Centipede 10-2 Motor proteins 10-6 Molecular diffusion in liquids 10-7 Physics 207: Lecture 3, Pg 5 Average Acceleration Average Acceleration c The average acceleration of a particle as it moves is defined as the change in the instantaneous velocity vector divided by the time interval during which that change occurs. c Note: bold fonts are vectors a c The average acceleration is a vector quantity directed along v Physics 207: Lecture 3, Pg 6 Instantaneous Acceleration Instantaneous Acceleration c The instantaneous acceleration is the limit of the average acceleration as v / t approaches zero Page 2 Physics 207 Lecture 2 Physics 207: Lecture 3, Pg 7 Instantaneous Acceleration Instantaneous Acceleration...
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