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This 2 page Study Guide was uploaded by Usman Qureshi on Wednesday November 18, 2015. The Study Guide belongs to a course at a university taught by a professor in Fall. Since its upload, it has received 14 views.
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Date Created: 11/18/15
3 Last Lecture 3 More WorkEnergy 3 Start of Potential Energy 3Today 3 More on WorkEnergy including Potential Energy 3 Important Concepts 3 Don t double count by including a force in both the Work and the Potential Energy 3 Don t forget to include the Work term it is only zero under special conditions 801 L Fall 2005 10272005 Important Reminders 3 Pset 6 due tomorrow at 10am 3Next Mastering Physics deadline is next Monday 3 Exam 2 is next Friday at 10 am 3 Covers material through today s lecture tomorrow s problemsolving and Pset and Monday s MasteringPhysics assignment 3 Experiment 4 will be done next Tuesday 3 Info on exam and experiment will be posted soon 801 L Fall 2005 10272005 Checklist to use WorkEnergy 3Clearly define what is inside your system 3Clearly define the initial and final conditions which include the location and speed of all objects 3Think carefully about all forces acting on all objects 3All forces must be considered in the Work term or in the Potential Energy term but never in both WAEEFinal E Initial KEFinal PEFinal Initial P E Initial 801 L Fall 2005 10272005 Potential Energy 3 Only applies for a force with special properties so called conservative forces 3 For your purposes there are very few 1Gravity both near to and far from the Earth 2 Springs 3 Problems where you don t know the force but are given the Potential Energy explicitly 3 You are only responsible for knowing the PE for gravity near Earth Mgh and option 3 on Exam 2 801 L Fall 2005 10272005 Calculating Potential Energy 3 For simplicity the Potential Energy itself as opposed to the difference is always defined relative to some reference point where the potential energy is defined to be zero The location of this point is totally arbitrary because only the change in potential energy is ever important Define arbitrarily PE at point A 0 B Then PE at point B J13d A 801 L Fall 2005 10272005 Using Potential Energy to Calculate Force B gtlf PEB jFd A 3Then sz duDE F dx y dy OGiven F you can find PE and vice versa 801 L Fall 2005 10272005 Potential Energy Diagrams PE J d Em I e x m b c 3PE as a function of position a Figure by MIT OCW 3 If there are no other forces doing nonzero Work then the total energy is a flat line on this plot 3And the KE is the difference see next slide 3 KEETotPE 801 L Fall 2005 10272005 Potential Energy Diagrams PE J KE lt 0 KB O Unphysicalll Object stops ETot Small KE Large KE Places Where FX O X m 801L Fall 2005 Figure by MIT OCW 10272005
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