TO THE STUDENT 2
ENERGY 3
Introduction 5
Unit 1 What is Energy? 6
Unit 5 Hot Wires 7
Unit 2 Burning Fuels 11
Unit 3 Fuels from Under the Ground 17
Unit 4 Electricity 22
Unit 5 Solving Energy Problems 33
Unit 6 What Can You Do? 43
Show What You Learned 48
ELECTRICITY 49
Introduction 51
Unit 1 A Special Path 52
Unit 2 On and Off 59
Unit 3 Go with the Flow 65
Unit 4 Electric Light 71
Unit 6 Beware of Bare Wires 83
Unit 7 Watch Out! 89
Show What You Learned 94
SOUND 95
Introduction 97
Unit 1 Making Sounds 98
Unit 2 High Sounds and Low Sounds 105
Unit 3 Sound Travels 113
Unit 4 What Sound Travels Through 119
Unit 5 Sound Changes Direction 127
Unit 6 Using What You Know 135
Show What You Learned 140
MACHINES 141
Introduction 143
Unit 1 Making Work Easy 144
Unit 2 The Inclined Plane 149
Unit 3 The Wedge 156
Unit 4 The Lever 162
Unit 5 The Wheel and Axle 169
Unit 6 The Pulley 176
Unit 7 Using Machines 183
Show What You Learned 186
GLOSSARY 187