EGR 1301 Lecture Notes - Lecture 19: Rubber Band, Potential Energy, Electric Blanket
7 Dec 2016
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Document Summary
A particular subset of the universe specified in time and space by a boundary. Once a system is specified, itc cannot be changed midway through a calculation. The system boundary can be any shape but must be a closed surface. System boundary can be rigid or flexible. Final balance - initial balance = deposits - withdrawals. Final balance = initial balance + deposits - withdrawals. Final energy - initial energy = input - output. State quantities accumulated energy path quantities energy in/out. Potential energy: energy associated with position, either against a field gravity or electrical field) compressed spring, or stretched rubber band. Work: energy flow due to oa driving force other than temperature. (mechanical (shaft, hydraulic), electrical photonic, (laser, solar pv) Ek + e p + u = w in - w out + q in - q out + m in - m out. Work input = work done on the system.
