Chapter 6 chapter 7 ghapter 8 chapter 9 chapter l0

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Chapter 6 Chapter 7 Ghapter 8 Chapter 9 Chapter l0 Chapter ll Chapter 12 Chapter 13 Fundamental Dlmensions and Units Length and Length-Related Parameters Tlme and Tlme-Related Parameters Mass and Mass-Related Parameters Force and Force-Related Parameters Temperature and Temperature-Related Parameters Electrlc Current and Related Parameters Energy and Power
CHAPTER 6 FuNDAMENTAL D rnnENs roNs AND Uxrrs group of engineers preparing for the test flight of the Pathfinder, a solar-powered, remote-piloted aircraft. The Pathfinder was constructed of composite materials, plastics, and foam to create a lightweight aircraft. The aircraft has a wingspan of 30 m and a gross mass ot221kg.lt is capable of moving at a speed of 7 m/s and is powered by a solar array that runs 6 electric motors which turn the propellers. Among other activities, NASA is interested in using the aircraft to study the upper atmosphere without disturbing it. 126 !-:'.U:jli!l1ir.!::-----r:{1.:!ilAr-----.!!:t1si!a:!----- ---rrir.!:!:l
6.1 ExcrNrsRrNc PnoslErvrs eNo FuNpr,unNrel DrMsNsroxs 127 In this chapter, we will ex?hinfundammtal engineering dimensions, such as lmgth and time, and their units, such at rneter and second, and their role in mgineering analysis and design. '4s an engineering studant, and later as praaicing engi.neer, whm perforrntng an analysis, you will fnd a need to conuert frorn one systern of units to anotlrer. Ve will expkin the stelts necessar! to conuert informationfrorn one slsteln ofunits to annther corre$b, In this chaptn, we will also emphasize thefact thatyou musr always show the a?praprinte anits that go with yur calcuhtions. Finally, we will explain what is rneant by an mgineering rystem and an mgineering corn?onent, 6.1 Engineering Problems and Fundamental Dimensions The eyolution of the human intellect has taken shape over a period of thousands ofyears. Men and women all over the wodd observed and learned from their surroundings. They used the knowledge gained from their observations ofnature to design, dwelop, test, and fabricate tools, shelter, wenpons, water transportation, and means to cultivate and produce more food. More- over, they realized that they needed only a few physical quantities to firlly describe natural wents and their surroundings. For erample, the length dimension was needed to describe how tall or how long or how wide something was. They also learned that some things are heavier than other things, so there was a need for another physical quantiry to describe that observa- don: the concept of mass and weight. Early humans did not firlly understand the concept of gravitf consequendy, the correct disdncdon between mass and weight was made later. Time was another phpical dimension that humans needed to understand in order ro be able to enplain their surroundings and to be able to answer questions such as: "How old are you?' "How long does it take to go from here to there?" "How long does it take to cook this food over fire?" The response to these questions in those early days may have been something like this: "I am many many Moons old," or "It takes a couple of Moons to go from

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