1lesson 4II. Energy and the First Law of ThermodynamicsA. Energy Transfer by Work. Energy is Conserved.1. Energy can cross the boundary of a closed system by only two mechanisms: heat transfer and work transfer.2. The change in energy of a closed system is equal to the net heat transferred to the system minus the net workperformed by the system.,,sysin netout netEQW∆=−Closed systemNet work out, Wout,net= Wout - WinNet heat in, Qin,net= Qin- Qout(2-34), p. 73; (4-17), p 174totalsystemsurroundingsEEE0∆∆∆=+=systemsurroundingsEE∆∆= −lesson 4II. Energy and the First Law of ThermodynamicsB. Mechanical work and power1. Introductiona. Work done by force F on a body displaced distance s is b. Power supplied to body moving with velocity V:)kW(FWV=±)kJ(FsW=)kJ(dsFW21∫=(2-22)ConstantforceVariableforceFs21W = areaunder curves2s1
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