POTENTIAL)机械能.pptVIP

Energy By Yeung Chung Kuen (12/03/2006) Revised by Mak What is Energy ? Basic Definitions. Forms of Energy. A Short History of Energy. Dangerousness of Energy. Renewable Energy. Resources Related to Energy. What is energy ? Energy makes change; it does things for us. It moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. It makes our bodies grow and allows our minds to think. ……. Basic Definitions A very good definition of energy is: Energy is the ability to do work. In common sense, work is get things done. In physics, ‘work’ is force x displacement, W = Fs. Forms of Energy Mechanical( Kinetic and potential)機械能(動能和位能) Chemical 化學能 Heat 熱能 Electric 電能 Light 光能 Sound 聲能 Nuclear 核能 People have learned how to change energy from one form to another so that we can do work more easily and live more comfortably. Potential Energy Kinetic energy Mechanical Energy Chemical Energy Chemical Heat +Light Energy Light/Heat Energy Electric/Light/Sound Energy Light Energy Sound/Light/Heat/Mechanical Energy Nuclear Energy by Fission A Short History of Energy The Old Days Before the industrial revolution(工業革命), our energy needs were modest(適度的 ). Examples For heat, we relied on the sun -- and burned wood, straw, and dried dung(糞肥) when the sun failed us. For transportation, the muscle of horses and the power of the wind in our sails took us to every corner of the world. For work, we used animals to do jobs that we couldnt do with our own labor. Water and wind drove the simple machines that ground our grain and pumped our water. B.C.500,000-300,000 Use of fire Man started to use fire a half million years ago. Ancient people knew the fire through lightning, forest-fire, explosi