Chapter_7 - Ch 7: Work and Kinetic Energy Focus: Work by...

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Ch 7: Work and Kinetic Energy Focus: Work by external forces changes kinetic energy θ cos F d W = Work W: F Force component along displacement does work: θ Fcos θ d No work if d F Unit of work: Newton- meter = Joule = energy Sign: W > 0, energy transfer to system. W < 0, energy transfer from system: d , F opposite direction Memorize this!
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Ch 7: Work and Kinetic Energy Can Normal forces do work? Yes , if parallel to the velocity: 1 2 v N 1 No , if perpendicular to the velocity: v N Can radial forces do work for uniform circular motion?
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Ch 7: Work and Kinetic Energy z z y y x x B A B A B A + + B A Scalar Product A B = 2 2 2 2 A A A = + + = z y x A A A Note: Why do this? x y θ 1 A θ 2 B A x =Acos θ 1 A y =Asin θ 1 B x =Bcos θ 2 B y =Bsin θ 2 ) sin sin cos (cos 2 1 2 1 θ + = + AB B A B A y y x x B A 1 2 = AB Angle between A and B AB AB AB cos ) cos( 1 2 = = B A Scalar: Independent of x-y axis orientation, zero for θ ΑΒ = 90 o d F = W
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This note was uploaded on 05/13/2010 for the course PHYSICS 53L taught by Professor Mueller during the Fall '07 term at Duke.

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Chapter_7 - Ch 7: Work and Kinetic Energy Focus: Work by...

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