Physics I For Dummies

An easy-to-follow guide to introductory physics, from the Big Bang to relativity

All science, technology, engineering, and math majors in college and university require some familiarity with physics. Other career paths, like medicine, are also only open to students who understand this fundamental science. But don’t worry if you find physics to be intimidating or confusing. You just need the right guide!

In Physics I For Dummies, you’ll find a roadmap to physics success that walks you through every major topic in introductory physics, including motion, energy, waves, thermodynamics, electromagnetism, relativity, and more. You’ll learn the basic principles and math formulas of physics through clear and straightforward examples and instruction, and without unnecessary jargon or complicated theory.

In this book, you’ll also find:

• Up-to-date examples and explanations appearing alongside the latest discoveries and research in physics, discussed at a level appropriate for beginning students
• All the info found in an intro physics course, arranged in an intuitive sequence that will give first-year students a head start in their high school or college physics class
• The latest teaching techniques to ensure that you remember and retain what you read and practice in the book

Physics I For Dummies is proof that physics can fun, accessible, challenging, and rewarding, all at the same time! Whether you’re a high school or undergraduate student looking for a leg-up on basic physics concepts or you’re just interested in how our universe works, this book will help you understand the thermodynamic, electromagnetic, relativistic, and everything in between.

Dr. Steven Holzner has written more than 40 books about physics and programming. He was a contributing editor at PC Magazine and was on the faculty at both MIT and Cornell. He has authored Dummies titles including Physics For Dummies and Physics Essentials For Dummies. Dr. Holzner received his PhD at Cornell.

Introduction 1

About This Book 1

Conventions Used in This Book 1

What You’re Not to Read 2

Foolish Assumptions 2

How This Book Is Organized 2

Part 1: Putting Physics into Motion 2

Part 2: May the Forces of Physics Be with You 3

Part 3: Manifesting the Energy to Work 3

Part 4: Laying Down the Laws of Thermodynamics 3

Part 5: The Part of Tens 3

Icons Used in This Book 4

Beyond the Book 4

Where to Go from Here 4

Part 1: Putting Physics into Motion 5

Chapter 1: Using Physics to Understand Your World 7

What Physics Is All About 8

Observing the world 8

Making predictions 9

Reaping the rewards 9

Observing Objects in Motion 10

Measuring speed, direction, velocity, and acceleration 10

Round and round: Rotational motion 11

Springs and pendulums: Simple harmonic motion 11

When Push Comes to Shove: Forces 12

Absorbing the energy around you 13

That’s heavy: Pressures in fluids 13

Feeling Hot but Not Bothered: Thermodynamics 14

Chapter 2: Reviewing Physics Measurement and Math Fundamentals 15

Measuring the World around You and Making Predictions 16

Using systems of measurement 16

From meters to inches and back again: Converting between units 17

Eliminating Some Zeros: Using Scientific Notation 20

Checking the Accuracy and Precision of Measurements 21

Knowing which digits are significant 21

Estimating accuracy 23

Arming Yourself with Basic Algebra 24

Tackling a Little Trig 25

Interpreting Equations as Real-World Ideas 26

Chapter 3: Exploring the Need for Speed 29

Going the Distance with Displacement 30

Understanding displacement and position 30

Examining axes 31

Speed Specifics: What Is Speed, Anyway? 34

Reading the speedometer: Instantaneous speed 34

Staying steady: Uniform speed 35

Shifting speeds: Nonuniform motion 35

Busting out the stopwatch: Average speed 35

Speeding Up (Or Down): Acceleration 38

Defining acceleration 38

Determining the units of acceleration 38

Looking at positive and negative acceleration 39

Examining average and instantaneous acceleration 42

Taking off: Putting the acceleration formula into practice 42

Understanding uniform and nonuniform acceleration 44

Relating Acceleration, Time, and Displacement 44

Not-so-distant relations: Deriving the formula 45

Calculating acceleration and distance 46

Linking Velocity, Acceleration, and Displacement 48

Finding acceleration 49

Solving for displacement 50

Finding final velocity 51

Chapter 4: Following Directions: Motion in Two Dimensions 53

Visualizing Vectors 54

Asking for directions: Vector basics 54

Looking at vector addition from start to finish 55

Going head-to-head with vector subtraction 56

Putting Vectors on the Grid 57

Adding vectors by adding coordinates 57

Changing the length: Multiplying a vector by a number 59

A Little Trig: Breaking Up Vectors into Components 59

Finding vector components 60

Reassembling a vector from its components 62

Featuring Displacement, Velocity, and Acceleration in two dimensions 65

Displacement: Going the distance in two dimensions 66

Velocity: Speeding in a new direction 69

Acceleration: Getting a new angle on changes in velocity 70

Accelerating Downward: Motion under the Influence of Gravity 72

The golf-ball-off-the-cliff exercise 72

The how-far-can-you-kick-the-ball exercise 75

Part 2: May the Forces of Physics Be with You 79

Chapter 5: When Push Comes to Shove: Force 81

Newton’s First Law: Resisting with Inertia 82

Resisting change: Inertia and mass 83

Measuring mass 84

Newton’s Second Law: Relating Force, Mass, and Acceleration 84

Relating the formula to the real world 85

Naming units of force 86

Vector addition: Gathering net forces 86

Newton’s Third Law: Looking at Equal and Opposite Forces 92

Seeing Newton’s third law in action 92

Pulling hard enough to overcome friction 93

Pulleys: Supporting double the force 94

Analyzing angles and force in Newton’s third law 95

Finding equilibrium 98

Chapter 6: Getting Down with Gravity, Inclined Planes, and Friction 101

Acceleration Due to Gravity: One of Life’s Little Constants 102

Finding a New Angle on Gravity with Inclined Planes 102

Finding the force of gravity along a ramp 103

Figuring the speed along a ramp 105

Getting Sticky with Friction 105

Calculating friction and the normal force 106

Conquering the coefficient of friction 107

On the move: Understanding static and kinetic friction 108

A not-so-slippery slope: Handling uphill and downhill friction 110

Let’s Get Fired Up! Sending Objects Airborne 115

Shooting an object straight up 115

Projectile motion: Firing an object at an angle 117

Chapter 7: Circling Around Rotational Motion and Orbits 119

Centripetal Acceleration: Changing Direction to Move in a Circle 120

Keeping a constant speed with uniform circular motion 120

Finding the magnitude of the centripetal acceleration 122

Seeking the Center: Centripetal Force 123

Looking at the force you need 123

Seeing how the mass, velocity, and radius affect centripetal force 124

Negotiating flat curves and banked turns 125

Getting Angular with Displacement, Velocity, and Acceleration 128

Measuring angles in radians 128

Relating linear and angular motion 129

Letting Gravity Supply Centripetal Force 131

Using Newton’s law of universal gravitation 131

Deriving the force of gravity on the Earth’s surface 132

Using the law of gravitation to examine circular orbits 133

Looping the Loop: Vertical Circular Motion 137

Chapter 8: Go with the Flow: Looking at Pressure in Fluids 141

Mass Density: Getting Some Inside Information 142

Calculating density 142

Comparing densities with specific gravity 143

Applying Pressure 144

Looking at units of pressure 144

Connecting pressure to changes in depth 145

Hydraulic machines: Passing on pressure with Pascal’s principle 149

Buoyancy: Float Your Boat with Archimedes’s Principle 151

Fluid Dynamics: Going with Fluids in Motion 153

Characterizing the type of flow 154

Picturing flow with streamlines 156

Getting Up to Speed on Flow and Pressure 156

The equation of continuity: Relating pipe size and flow rates 157

Bernoulli’s equation: Relating speed and pressure 160

Pipes and pressure: Putting it all together 160

Part 3: Manifesting the Energy to Work 165

Chapter 9: Getting Some Work Out of Physics 167

Looking for Work 167

Working on measurement systems 168

Pushing your weight: Applying force in the direction of movement 168

Using a tow rope: Applying force at an angle 170

Negative work: Applying force opposite the direction of motion 172

Making a Move: Kinetic Energy 173

The work-energy theorem: Turning work into kinetic energy 173

Using the kinetic energy equation 174

Calculating changes in kinetic energy by using net force 175

Energy in the Bank: Potential Energy 177

To new heights: Gaining potential energy by working against gravity 178

Achieving your potential: Converting potential energy into kinetic energy 179

Choose Your Path: Conservative versus Nonconservative Forces 180

Keeping the Energy Up: The Conservation of Mechanical Energy 181

Shifting between kinetic and potential energy 181

The mechanical-energy balance: Finding velocity and height 184

Powering Up: The Rate of Doing Work 185

Using common units of power 186

Doing alternate calculations of power 187

Chapter 10: Putting Objects in Motion: Momentum and Impulse 191

Looking at the Impact of Impulse 191

Gathering Momentum 193

The Impulse-Momentum Theorem: Relating Impulse and Momentum 193

Shooting pool: Finding force from impulse and momentum 195

Singing in the rain: An impulsive activity 196

When Objects Go Bonk: Conserving Momentum 197

Deriving the conservation formula 198

Finding velocity with the conservation of momentum 199

Finding firing velocity with the conservation of momentum 200

When Worlds (Or Cars) Collide: Elastic and Inelastic Collisions 202

Determining whether a collision is elastic 203

Colliding elastically along a line 204

Colliding elastically in two dimensions 206

Chapter 11: Winding Up with Angular Kinetics 211

Going from Linear to Rotational Motion 212

Understanding Tangential Motion 213

Finding tangential velocity 213

Finding tangential acceleration 215

Finding centripetal acceleration 216

Applying Vectors to Rotation 218

Calculating angular velocity 218

Figuring angular acceleration 219

Doing the Twist: Torque 221

Mapping out the torque equation 223

Understanding lever arms 224

Figuring out the torque generated 225

Recognizing that torque is a vector 226

Spinning at Constant Velocity: Rotational Equilibrium .227

Determining how much weight Hercules can lift 228

Hanging a flag: A rotational equilibrium problem 230

Ladder safety: Introducing friction into rotational equilibrium 232

Chapter 12: Round and Round with Rotational Dynamics 237

Rolling Up Newton’s Second Law into Angular Motion 237

Switching force to torque 238

Converting tangential acceleration to angular acceleration 239

Factoring in the moment of inertia 239

Moments of Inertia: Looking into Mass Distribution 240

Merry-go-rounds and torque: A spinning-disk inertia example 242

Angular acceleration and torque: A pulley inertia example 244

Wrapping Your Head around Rotational Work and Kinetic Energy 246

Putting a new spin on work 246

Moving along with rotational kinetic energy 248

Let’s roll! Finding rotational kinetic energy on a ramp 249

Can’t Stop This: Angular Momentum 251

Conserving angular momentum 251

Satellite orbits: A conservation-of-angular-momentum example 252

Chapter 13: Springs ’n’ Things: Simple Harmonic Motion 255

Bouncing Back with Hooke’s Law 255

Stretching and compressing springs 256

Pushing or pulling back: The spring’s restoring force 256

Getting Around to Simple Harmonic Motion 258

Around equilibrium: Examining horizontal and vertical springs 258

Catching the wave: A sine of simple harmonic motion 260

Finding the angular frequency of a mass on a spring 266

Factoring Energy into Simple Harmonic Motion 269

Swinging with Pendulums 270

Part 4: Laying Down the Laws of Thermodynamics 273

Chapter 14: Turning Up the Heat with Thermodynamics 275

Measuring Temperature 276

Fahrenheit and Celsius: Working in degrees 276

Zeroing in on the Kelvin scale 277

The Heat Is On: Thermal Expansion 278

Linear expansion: Getting longer 278

Volume expansion: Taking up more space 280

Heat: Going with the Flow (Of Thermal Energy) 283

Getting specific with temperature changes 284

Just a new phase: Adding heat without changing temperature 286

Chapter 15: Here, Take My Coat: How Heat Is Transferred 291

Convection: Letting the Heat Flow 291

Hot fluid rises: Putting fluid in motion with natural convection 292

Controlling the flow with forced convection 293

Too Hot to Handle: Getting in Touch with Conduction 294

Finding the conduction equation 295

Considering conductors and insulators 299

Radiation: Riding the (Electromagnetic) Wave 300

Mutual radiation: Giving and receiving heat 301

Blackbodies: Absorbing and reflecting radiation 302

Chapter 16: In the Best of All Possible Worlds: The Ideal Gas Law 307

Digging into Molecules and Moles with Avogadro’s Number 308

Relating Pressure, Volume, and Temperature with the Ideal Gas Law 309

Forging the ideal gas law 310

Working with standard temperature and pressure 312

A breathing problem: Checking your oxygen 312

Boyle’s and Charles’s laws: Alternative expressions of the ideal gas law 313

Tracking Ideal Gas Molecules with the Kinetic Energy Formula 315

Predicting air molecule speed 316

Calculating kinetic energy in an ideal gas 317

Chapter 17: Heat and Work: The Laws of Thermodynamics 319

Getting Temperature with Thermal Equilibrium: the Zeroth Law 320

Conserving Energy: The First Law of Thermodynamics 320

Calculating with conservation of energy 321

Staying constant: Isobaric, isochoric, isothermal, and adiabatic processes 324

Flowing from Hot to Cold: The Second Law of Thermodynamics 338

Heat engines: Putting heat to work 338

Limiting efficiency: Carnot says you can’t have it all 341

Going against the flow with heat pumps 343

Going Cold: The Third (And Absolute Last) Law of

Thermodynamics 346

Part 5: The Part of Tens 349

Chapter 18: Ten Physics Heroes 351

Galileo Galilei 351

Sir Isaac Newton 352

Charles-Augustin de Coulomb 353

William Thomson (Lord Kelvin) 353

Marie Salomea Skłodowska Curie 353

Albert Einstein 354

Emmy Noether 355

Maria Goeppert Mayer 355

Chen-Shiung Wu 355

Jocelyn Bell Burnell 356

Chapter 19: Ten Wild Physics Theories 357

Time Slows Down 357

Moving Objects Contract 358

Heisenberg Says You Can’t Be Certain 358

Black Holes Don’t Let Light Out 359

Gravity Curves Space 359

Matter and Antimatter Destroy Each Other 360

Supernovas Are the Most Powerful Explosions 361

The Universe Starts with the Big Bang and Ends with the Gnab Gib 361

Microwave Ovens Are Hot Physics 362

Most Matter is Invisible 363

Glossary 365

Index 369

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