lecture chapter 7and8 reivew

# lecture chapter 7and8 reivew - A Quick Review for Chapter 7...

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24 K f -K i = ±K = W total ; ±E = W NC ; E f = W NC + E i W=F.d.cos ; : angle between force and motion! Work = force x distance along the force direction W friction = - f k .d , ( =180 ²), kinetic friction is against motion direction, usually does negative work. W N = N.d. (cos 90²) =0 , if motion is along the surface, which provides the normal force , (N ³ surface) (motion along incline, track, curved track and other surfaces), * Also, if Tension ³ to motion, it does zero work, like swing, pendulum… W mg = mg (hi-hf) = - mg ± h work done by gravity force is simply determined by weight and ±h, regardless trace … work done by gravity force converts energy between KE and gravitational PE. Use K+U , no need to calculate W mg . it’s already included as Potential Energy change. F spring = - k ± x , spring force is determined by spring’s stiffness and deformation ±x. Work done by spring converts energy between KE and elastic PE, U= ½ k(±x) 2

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25 K= ½ m v 2 , kinetic energy is proportional to m and v
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lecture chapter 7and8 reivew - A Quick Review for Chapter 7...

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