Physics 121, Sections 9, 10, 11, and 12 Lecture 12 Today's Topics Homework 5: Due Friday Oct 7@6: 00PM Ch.5:#9,11,12,23,26,30,32,41,57,and63. Review session Friday Oct 7@ 11: 00AM in IMS-20 Chapter 6: Work and Energy Forms of energy Definition of work Work-kinetic energy theorem Examples Physics 121: Lecture 12, Pg 1
Physics 121: Lecture 12, Pg 1 Physics 121, Sections 9, 10, 11, and 12 Lecture 12 Today’s Topics: Homework 5: Due Friday Oct. 7 @ 6:00PM Ch.5: # 9, 11, 12, 23, 26, 30, 32, 41, 57, and 63. Review session: Friday Oct. 7 @ 11:00AM in IMS-20 Chapter 6: Work and Energy Forms of energy Definition of work Work-kinetic energy theorem Examples
Summary (with comparison to 1-D kinematics) Angular Linear a= constant a= constant V= Vo+at 0=00+Oot+ ot+at And for a point at a distance R from the rotation axis X=RO V=OR a= ar Physics 121: Lecture 12, Pg 2
Physics 121: Lecture 12, Pg 2 Summary (with comparison to 1-D kinematics) Angular Linear = constant = 0 +0 + 1 2 2 t t a = constant v = v + at 0 x = x + v t + at 0 0 1 2 2 And for a point at a distance R from the rotation axis: x = R v = R a = R
Work Energy One of the most important concepts in physics Alternative approach to mechanics Many applications beyond mechanics Thermodynamics(movement of heat Quantum mechanics ery useful tools You will learn new(sometimes much easier) ways to solve problems Physics 121: Lecture 12, Pg 3
Physics 121: Lecture 12, Pg 3 Work & Energy One of the most important concepts in physics. Alternative approach to mechanics. Many applications beyond mechanics. Thermodynamics (movement of heat). Quantum mechanics... Very useful tools. You will learn new (sometimes much easier) ways to solve problems
Forms of Energy Kinetic: Energy of motion A car on the highway has kinetic energy We have to remove this energy to stop it The breaks of a car get Hot! This is an example of turning one form of energy into another(thermal energy) Kinetic energy is given by: K=(1/2)mv2 Physics 121: Lecture 12, Pg 4
Physics 121: Lecture 12, Pg 4 Forms of Energy Kinetic: Energy of motion. A car on the highway has kinetic energy. We have to remove this energy to stop it. The breaks of a car get HOT ! This is an example of turning one form of energy into another (thermal energy). Kinetic energy is given by: K = (1/2) mv2
Energy Conservation Energy cannot be destroyed or created Just changed from one form to another We say energy is conserved! True for any isolated system i. e when we put on the brakes, the kinetic energy of the car is turned into heat using friction in the brakes. The total energy of the " car-breaks-road-atmosphere" system is the same The energy of the car alone" is not conserved > It is reduced by the braking Doing "work on an otherwise isolated system will change it's energy Physics 121: Lecture 12, Pg 5
Physics 121: Lecture 12, Pg 5 Energy Conservation Energy cannot be destroyed or created. Just changed from one form to another. We say energy is conserved ! True for any isolated system. i.e when we put on the brakes, the kinetic energy of the car is turned into heat using friction in the brakes. The total energy of the “car-breaks-road-atmosphere” system is the same. The energy of the car “alone” is not conserved... »It is reduced by the braking. Doing “work” on an otherwise isolated system will change it’s “energy