Chapter 8 Potential Energy and Conservation of Energy 第八章 位能與能量守恆

Chapter 8 Potential Energy and Conservation of Energy 8-1 What is Physics? 8-2 Work and Potential Energy 8-3 Path Independence of Conservative Forces 8-4 Determining Potential Energy Values 8-5 Conservation of Mechanical Energy 8-6 Reading a Potential Energy Curve 8-7 Work Done on a System by an External Force 8-8 Conservation of Energy

8-1 What is Physics? Potential Energy 位能 ( U ) –Gravitational Potential Energy 重力位能 –Elastic Potential Energy 彈力位能、彈性位能 –Electrical Potential Energy 電位能 Technically, potential energy is energy that can be associated with the configuration of a system of objects that exert forces on one another

bungee 鬆緊繩 bungee-cord bungee-cord jumper plunge 跳下

8-2 Work and Potential Energy Conservative Force 守恆力、保守力 –Gravitational Force –Spring Force Nonconservative Force 非守恆力、非保守力 –Kinetic frictional force –Drag force Thermal Energy 熱能 –Thermal energy is not a potential energy

8-3 Path Independence of Conservative Forces 與路徑無關的守恆力 –The net work done by a conservative force on a particle moving around any closed path is zero –The work done by a conservative force on a particle moving between two points does not depend on the path taken by the particle

Sample Problem

8-4 Determining Potential Energy Values Reference point 參考點、基準點

Sample Problem

8-5 Conservation of Mechanical Energy 力學能守恆 Mechanical Energy 力學能 –Kinetic energy 動能 –Potential energy 位能 Principle of Conservation of Mechanical Energy 力學能守恆原理

Sample Problem

8-6 Reading a Potential Energy Curve turning point 轉折點 equilibrium point 平衡點

轉折點與平衡點 turning point 轉折點 equilibrium point 平衡點 –unstable equilibrium –stable equilibrium

Sample Problem

8-7 Work Done on a System by an External Force

8-8 Conservation of Energy Law of Conservation of Energy 能量守恆定律、能量守恆律 Internal energy 內能 Isolated system 隔離系統、孤立系統

Sample Problem