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Unformatted text preview: ME 200: Thermodynamics I Lecture 4: Mechanical concepts of Energy and Work Prof. Sojka Summer 2011 2 In this Lecture Mechanical Concepts of Energy Work 3 Kinetic Energy Kinetic Energy Is a scalar quantity Is an extensive property Its change can be related to Work Change in Kinetic Energy , KE dt dV m F s = 1 2 KE KE KE = 2 1 2 2 2 1 V Vm KE = KE sdF s s = 2 1 2 2 1 mV KE = 4 Kinetic Energy Example An object of mass 1000 kg, initially having a velocity of 100 m/s, decelerates to a final velocity of 20 m/s. What is the change in kinetic energy of the object, in kJ? Given m = 1000 kg V 1 = 100 m/s V 2 = 20 m/s Find KE = ? in kJ Sketch Assumptions The object is a closed system. Basic Equations Solution m 2 1 2 2 2 1 V Vm KE = (29 mN kJ smkg N s m kg KE  = 3 2 2 2 2 2 10 1 1 1 100 20 1000 2 1 kJ KE 4800 5 Potential Energy Potential Energy Is also an extensive property...
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 Summer '08
 GAL

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