Physics 3 – Sept 1, 2016 Do Now: P3 Challenge – (Answers only on paper – report energies in kJ ) A 60 kg bungee jumper jumps from a bridge. She is tied to a 12 m long bungee cord and falls a total of 31 m. a) How much gravitational potential energy does she have before jumping. (Set the origin of your frame of ref at the bottom of her fall.) b) How much kinetic energy does she have when she stops freefalling and the bungee is not yet stretching? c) What velocity does she have when the bungee starts to stretch? d) How much energy is absorbed by the bungee and stored as spring potential energy? e) What is the spring constant, k, of the bungee cord? f) How much work does gravity do on the girl during the jump? g) How much work does the bungee cord do on the girl during the jump?

Objectives/Agenda Objective: Work and Energy Agenda: P3 question to review kinetic energy, gravitational potential energy, spring potential energy, conservation of energy, work-kinetic energy theorem, calculation of work Additional problem solving to practice. Assignment: Prepare for Unit 3-5 Mastery Quizzes Next week

About Work and Energy Sign convention: + work on a system adds energy to the system - work on a system removes energy from the system Work kinetic energy theorem: Wnet = ∆K uses the NET work Conservation of mechanical Energy only applies if only conservative forces are present. (Gravity, spring, electrical etc…) Nonconservative forces: friction, air resistance, etc… For every conservative force, there is a corresponding potential energy.

Topics Reviewed Sept 1 Bungee jumper combination of gravitational and spring potential energies Work on an incline, with and without friction Kinetic energy of an oxygen molecule Work done to catch a baseball Energy considerations for a pole vaulter, a high jumper and a trampoline artist Energy of a mass on a vertical spring.

Today’s Assignment Continue reviewing 2.2, 2.3, 2.4 Prepare for Unit 3-5 Mastery Quizzes Next week Mastery quizzes are worth 10 points and will be two multiple choice questions with 8 points of problems. (Usually one or two problems). IB materials will be integrated as much as possible. May retake mastery quizzes as needed to reach 8/10 proficiency level. See me during Lunch or after school. Schedule your retakes and give me at least 24 hours to prepare the quiz for you