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Unformatted text preview: The concept of energy (and the conservation of energy chapter 8) is one of the most important topics in physics. Work Kinetic energy Energy approach (system model) is often simpler than Newtons second law (particle model). Scalar product (dot product); work is scalar product of force and displacement. Hookes law, springs Power Chapter 7: Work; Energy of a System Reading assignment: Chapter 7 Homework : CQ1, CQ5, QQ1, QQ2, AE2, 1, 9, 11, 12, 14, 15, 17, 25, 27, 31, 33, 42, 43 Due dates: Tu/Th, and MWF section : Monday, Feb. 28 Remember HW 6 due Monday, Feb. 21 Work (as defined by a physicist) Definition: The work done on an object by an external force is: the product of the component of the force in the direction of the displacement and the magnitude of the displacement. cos = d F W How much work is done when just holding up an object? = = W d F W cos How much work is done when the displacement is perpendicular to the force? = = W d F W cos What is the work done when lifting? (at constant speed) By the applied force? By the gravitational force? = = W d F W cos Sign convention: W positive: If F and d are parallel . If energy is transferred into the system. W negative: If F and d are antiparallel . If energy is transferred out of the system....
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 Spring '09
 Energy, Work

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