Popular in Course
verified elite notetaker
Popular in Department
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 15 views.
Reviews for lec16
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 11/18/15
3 Last Lecture 3 Potential Energy examples 3Today 3 Potential Energy diagrams Potential Energy of springs 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 801L Fall 2005 1112005 Important Reminders 3 Exam 2 is this Friday at 10 am 3 Covers material through last Thursday s lecture last Friday s problemsolving and Pset and yesterday s MasteringPhysics assignment 3QampA review session Thur 7830pm 3 Experiment 4 will be done today 801 L Fall 2005 1112005 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 1112005 Potential Energy Diagrams PE D d 3 PE as a function of posmon Em C x m b c a Figure by MT 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 KEEToPE 801 L Fall 2005 1112005 Potential Energy Diagrams KE ETot P E PE J KE lt 0 KB 0 Unphysicalll Object stops X ETot 39 Small KE Large KE X m Places Where FX O 801 2005 Figure by MIT OCW Potential Energy of Springs 3The force is F ki i0 L 2 330 the PE isPEL j kl lodlkL lo lo 3 Note We define PEO at the unstretched length 1 801 L Fall 2005 1112005 Vertical Spring plus Gravity 3Let PEO hO and yO at the unstretched position PEy ky2 mgy 3Now something strange happens 2 2 2 PEy ky2 mgy ky m2 3Another parabola but offset in y and in PE scale 3 It is mgk the point where the spring and gravity exactly balance to give zero total force 801L Fall 2005 1112005 Summary 3 Potential energy diagrams can be a useful tool for conceptual understanding of some energy problems 3Minima and maxima of the PE correspond to FO which are equilibrium points PE minima are stable equilibrium points maxima are unstable 3 For springs PEL kL 102 3 Except for this formula springs introduce no new concepts to the WorkEnergy formalism but sometimes unexpected results appear 801 L Fall 2005 1112005
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'