lecture4 - 8/30/2010 MechanicalConceptsofEnergy, Work ME200...

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8/30/2010 1 Mechanical Concepts of Energy, Work ME 200 Thermodynamics I Purdue University , Dr. Tim Pourpoint – timothee@purdue.edu Lecture 4 August 30 th , 2010 Last Week Fundamental Thermodynamic Concepts – Definitions – Dimensions/Units –Cy c le s – Pressure – Closed/Open Systems – Properties – State & equilibrium – Processes – Energy – Temperature ME 200 2
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8/30/2010 2 Today’s agenda –Wo rk and Kinetic Energy –Po ten t ia l Energy Conservation of Energy in Mechanic This Lecture – Conservation of Energy in Mechanics – Sign Convention and Notation in Thermodynamics •W > 0 : work done by the system •W < 0 : work done on the system •S ign convention is the opposite of that in mechanics – Mechanical and non mechanical forms of work ME 200 3 Acknowledgement: Prof. Eckhard A. Groll (ME) for slides Forms of Energy (PE) energy Potential M From last week: Forms of energy “you U PE KE E (U) energy Internal c Microscopi (KE) energy Kinetic c Macroscopi Total energ can see” Forms of energy “that are hidden” Related to molecular structure and activity ME 200 4 Total energy: TOTAL ENERGY = MICROSCOPIC FORMS OF ENERGY MACROSCOPIC FORMS OF ENERGY +
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8/30/2010 3 Macroscopic Energy and Work • Mechanical Work: Energy transfer to or from a system due to a force acting through a distance s –Con s tan t force: –Va r iab le force: 2 1 Fds W Fds W ds (Force in direction of movement) Note: Force F causes object to accelerate or balance friction ME 200 5 – Instantaneous power: – Sign Convention: •W > 0 work done by the system (work output) •W < 0 work done on the system (work input) WF F V dt  ( V = velocity) Macroscopic Energy and Work • Kinetic Energy (KE): Work required to accelerate system to velocity V relative to reference frame, in the absence of an opposing force (no friction or gravity gravity) ; d s dV Fm a a dt  dV ds Notes: KE i ti t ME 200 6 Wm d sm d Vm V dV dt dt   2 22 21 1 1 2 VV V d V m m V V K E     KE is extensive property
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This note was uploaded on 09/19/2010 for the course ME 200 taught by Professor Gal during the Spring '08 term at Purdue University-West Lafayette.

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lecture4 - 8/30/2010 MechanicalConceptsofEnergy, Work ME200...

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