Janice VanCleave's Physics for Every Kid, Second Edition by Janice VanCleave

Janice VanCleave's Physics for Every Kid

Easy Activities That Make Learning Science Fun

 

 

 

Janice VanCleave

 

Second Edition

 

 

 

 

Logo: Wiley

Introduction

Throughout the writing of this book, I have daydreamed about the fun I have teaching hands-on physics. I've pictured children and educators enjoying these science activities, while reading instructions that are clear and easy to follow and simple explanations about what happened and why. Science safety was a primary concern when designing the activities in this book. It is my fervent hope that this physics book will ignite a profound curiosity for scientific discovery in readers of all ages. The bottom line is that I want to share my passion for physics and how exciting and relevant science is to our everyday lives.

One doesn't need a degree in science to benefit from learning more about why magnets stick to the fridge door and not to a wooden door. Wonder how a parachute works? Why does a magnifying glass make things look bigger? I imagine children of all ages stopping and questioning the physical world around us. Scientific investigations help develop patterns and higher-level thinking to solve real, everyday problems.

The order of presentation is designed to provide a physics foundation upon which to build new principles of science. The activities in each specific topic spiral in content. Throughout the activities, certain words and phrases are in bold; the meanings of these are given in the Glossary at the end of the book. Working through the activities in order is suggested. However, any activity has educational value on its own merit. With the help of the Glossary, as well as introductions for various topics, you can pick and choose any investigation and be rewarded with a successful experiment. Of course, a good outcome depends upon following the procedure steps in order. Substituting equipment can affect the results for some activities, but science is meant to be fun so trust your judgment about changes.

This book was designed to give the reader a taste of physics:

  • Energy Learn about stored energy, energy of moving objects and the transfer between them, and the study of different forms of energy including mechanical, electrical, sound, and light. Energy is simply the ability to do work, which means to change or deform or move an object, and to create heat.
  • Force and Motion Learn about the effect of forces acting on an object, and study about the force of gravity and how it affects falling objects. A study of Sir Isaac Newton's Three Laws of Motion and how they apply to our everyday lives is covered.
  • Simple Machines Learn about simple machines which are mechanical devices that change the direction and/or magnitude (size) of a force. Levers, inclined planes, wedges, wheels and axles, pulleys, and screws are studied.
  • Magnets Learn about magnets and their effect, including an invisible field around magnets responsible for the most remarkable property of a magnet, which is a force that pulls on other magnetic materials, such as iron, and attracts or repels other magnets.

The Activities

This book is written to guide you through the steps necessary in successfully completing a science experiment and to present methods of solving problems and making discoveries.

  • Introduction: Background information provides knowledge about the topic of the investigation and generally describes cause and effect relationships that you can investigate.
  • See for Yourself: A list of common but necessary materials and step-by-step instructions on how to perform the experiment is provided.
  • What Happened? A statement of the predicted outcome is provided with a discussion of what should have happened during the activity. A scientific explanation of what was observed is provided using understandable language and technical, scientific vocabulary so that readers of any age can master the scientific principles involved and discuss their findings.

General Instructions

  1. Read first. Read each experiment completely before starting.
  2. Collect needed supplies. You will experience less frustration and more fun if all the necessary materials for the experiments are ready and set up for easy access.
  3. Experiment. Follow each step very carefully, never skip steps, and do not add your own. Safety is of the utmost importance. By reading the experiment before starting, you will be able to note any safety warnings. Then, follow instructions exactly so you can feel confident that your outcome will have the desired results.
  4. Observe. If your results are not the same as described in the experiment, carefully reread the instructions, and start over from the beginning. Check to make sure your materials are as described and in good working order. Use the illustrations to see if the activity is set up properly. Consider factors, such as the ambient temperature, humidity, lighting, and so on, that might affect the results.

Measurements

Measuring quantities described in this book are given in imperial units followed by approximate metric equivalents in parentheses. Unless specifically noted, the quantities listed are not critical, and a variation of a very small amount more or less will not alter the results.

Foreword

Imagine a toddler gleefully dropping a bottle off the highchair tray. Their parent returns the bottle to its rightful place only to see it dropped again. And each time the bottle falls to the floor. This toddler and Sir Isaac Newton have something in common. They both find physics delightful! Janice VanCleave knows that this toddler is learning about the laws of physics! This book is written for every kid who wants to keep dropping things, rolling things, and, most of all, wants to keep learning about the physical world.

And who hasn't wondered about how something as large as an airplane can stay up in the sky? Janice VanCleave never wants that sense of wonder to end. Written for people of all ages with a curiosity about the world around us, this book will be a treasure for the homeschooling parent or classroom teacher that wants to add easy-to-do science that promises to have kids asking, “Is it time for science yet?”

Each activity starts out with a clear explanation of a scientific phenomenon. We have all played with magnets. But did you know that you can map an invisible magnetic force field with a compass? Soon, you find yourself eagerly gathering a few common household materials because the activity is so enticing you can't wait to try it! Each science activity, often deceptively simple, is followed by an explanation that uses everyday language to explain complex principles. It is simply astounding to experiment with something that you have seen a million times, but for the first time you really understand the science. Wow.

Janice VanCleave is a teacher at heart. Her true passion is explaining science in a way that anyone can understand it. This book is a treasure. It unlocks the mystery of physical laws that we see every moment of every day.

I can't help but think that one day the baby who dropped the bottle off the highchair tray will open this book. Then, a true adventure of science discovery and learning will take place. Once again, exploring physics will be delightful! Perhaps that kid will grow up to be the first person to walk on Mars. Anything is possible.

Mary Bowen

I
Energy Introduction

Energy is the capacity to do work. In physics, work is done when a force is applied to an object causing it to move. A force is a pushing or pulling action on an object. Forces are measured in pounds (lb) or newtons (N), where 1 lb = 4.5 N. Work occurs only when a force causes something to move. If you push on a tree and it doesn't move, then no work has been done even though the effort may have exhausted you. Study how work is calculated in this important equation: W = F × d; where W is the work done; F is a specific force and d is the distance moved. Comparatively, when the equation is W = Fnet × d, the work being done considers all forces (Fnet) that are acting on the object that is being moved, including frictional forces. Weight is a measure of Earth's gravitational force pulling an object down toward the center of Earth. Gravity is the force of attraction between two objects with mass. Yes, your body has a force of attraction on other objects, but it is such a minute force that it is basically ineffective. Whereas, the mass of Earth is great enough to produce a force that pulls things on or near Earth's surface down. Down means toward the center of Earth; thus, when you drop something, it falls perpendicular to Earth's surface. Forces do not always cause linear motion, which is motion in a straight line. Torque is a turning force that causes motion around a center point, such as the turning of a lid or the spinning of a merry-go-round.

Movement is the change of an object's physical position. Linear movement is measured in feet (ft) or centimeters (cm), where 1 ft = 30 cm. Not all movement is linear or rotational but rather some objects vibrate, meaning they move back and forth. Frequency is a measure of the number of times something happens in a specific amount of time. Frequency can be measured in hertz (Hz), where 1 Hz = 1 cycle per second or one back and forth vibration.

Potential energy is the energy an object has because of its position relative to some zero position. It is energy that has the potential to do ‘work.’ Two types of potential energy investigated in this book are gravitational potential energy and elastic potential energy.

  • Gravitational potential energy is the stored energy an object has because of its position above a specific ground zero. This type of potential energy is due to the force of gravity acting on the object. To obtain this energy, work had to be done on an object to raise it to a higher level above ground zero, such as placing a book on a top shelf with the floor below being ground zero. Gravitational potential energy is directly related to the mass of the object as well as its height above ground zero. When the book is dropped from a specific height, its gravitational potential energy is converted to kinetic energy as the book falls.
  • Elastic potential energy is the energy stored in an object that can be stretched or compressed. A force is needed to compress or stretch an elastic object. Consider a trampoline, which has the greatest elastic potential energy when it is stretched the most, as does a rubber band. A coiled spring stores elastic potential energy when a force compresses it as well as when a force stretches it. In both cases, when the spring is released, the spring's elastic potential energy results in the wound coils moving back to their normal position. Thus, the elastic potential energy is converted to kinetic energy.

Kinetic energy (KE) is the energy of objects that are moving. Remember, kinetic energy does not cause an object to move, instead objects have kinetic energy because they are moving. A ball at the top of a ramp has gravitational potential energy. As the ball rolls down the ramp, its gravitational potential energy is converted to kinetic energy. There are three types of kinetic energy: vibrational, rotational, and translational. Vibrational KE is the energy caused by a back and forth movement; rotational KE is the result of turning about an axis, and translational KE is the result of linear movement from one place to another.

Mechanical energy is the sum of an object's potential energy and kinetic energy. Objects have mechanical energy if they are moving or have positional potential energy. Remember that an object doesn't have to be a machine to have mechanical energy. For example, both rivers and wind have mechanical energy.

In addition to mechanical energy activities, other types of energy will be investigated: sound energy, electrical energy, and light energy.

Sound is the sensation perceived by an organism's sense of hearing produced by the stimulation of hearing organs by sound waves. Sound energy is a type of energy produced by vibrating objects, such as when a guitar string is plucked. The movement of the string moves the air around it, producing a pattern of disturbances in the air called sound waves. Sound energy is transferred through mediums, such as solids, liquids, and gases. This type of energy can be heard by humans and other animals.

Electricity is a type of energy that we often take for granted until it is not available. All electric appliances, including computers and TVs do not work if the electric power line bringing electrical energy to your home is broken during a storm. You will discover more about current electricity as well as how to perform magic tricks using static electricity in the activities included in this book. You will also learn how the chemical energy stored in batteries produces the current electricity necessary for cell phones and tablets. Other electrical terms such as free electrons, conductors, insulators, polarization, and closed and open circuits will be investigated in the activities related to electrical energy.

Light energy is radiation. Radiation is a type of wave energy that does not need a medium to move through, such as radiation from the Sun that moves through space to Earth. The term radiation can sound dangerous and frightening, but did you know that common visible light and heat waves, called infrared light, are all forms of radiation? We can't imagine homes without our useful microwave oven. There are seven types of radiation: gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radiowaves.

1
Energy Conservation

The Law of Conservation of Energy states that energy is neither created nor destroyed. Instead, energy can be converted, or changed, into another form of energy. In this activity, the mechanical energy of a pendulum will be investigated. Mechanical energy is the summation of an object's potential energy (stored energy) and kinetic energy (energy of moving objects). A pendulum is a weight, called a bob, hung from a fixed point so that it can freely move backward and forward. Each swing of the bob, from one side to the other forms an arc, as shown in Figure 1. Work is done on the pendulum when it is raised to position A. This means that energy is being transferred to the pendulum. When raised, the pendulum gains gravitational potential energy, which is stored energy due to an object's height. When released, gravity pulls the pendulum down and its gravitational potential energy is converted into kinetic energy.

Gravity is the force of attraction between any two objects with mass in the Universe. The greater the mass, the greater is an object's gravitational force. Earth is very massive; thus, it attracts objects near or on its surface in a direction toward its center. At position A, the pendulum has maximum gravitational potential energy, which is changed to kinetic energy as the pendulum swings down to position B. From position B to C, the pendulum is moving against the downward force of gravity; thus, it slows. During this upward part of the swing, the pendulum's kinetic energy changes into gravitational potential energy again.

Schematic illustration of the mechanical energy of a pendulum that involves the transfer of kinetic energy into potential energy and back to kinetic energy and so on.

FIG 1

The mechanical energy of a pendulum involves the transfer of kinetic energy into potential energy and back to kinetic energy, and so on. It is important to note that the amount of potential energy at position C is less than it was when the pendulum was first lifted to position A (Figure 1). This means the pendulum loses mechanical energy with each swing and each swing is lower and lower until it finally stops. This lost energy was changed into another form of energy, such as heat or sound (air vibration).

See for Yourself

Materials

  • string, 8 inch (20 cm)
  • tape
  • washer with a hole or any comparable weight

What to Do

  1. Tie one end of the string to the washer.
  2. Tape the free end of the string to the edge of a table (Figure 2).
    Schematic illustration of the string that has been tied to the washer.

    FIG 2

  3. Pull the pendulum to the side a short distance and release. It should swing back and forth. Observe the movement of the pendulum. Make note of the pendulum's height during each swing.

What Happened?

In Figure 1 the pendulum is first held stationary at position A, which is higher than position C. This means work has been done on the pendulum by lifting it, giving the pendulum gravitational potential energy. When the pendulum is released, the force of gravity acts on the pendulum pulling it downward. When moving, the pendulum has kinetic energy. Halfway between A and B, half of the mechanical energy is divided between potential energy and kinetic energy. At position B, the potential energy of the pendulum is zero and the kinetic energy is at its maximum. This kinetic energy decreases as the pendulum moves toward position C. Halfway between B and C, mechanical energy is again divided between potential energy and kinetic energy. Finally, the pendulum rises slightly below position C. In this position, its potential energy is less than at the start of the swing. This reduction of mechanical energy decreases incrementally until the pendulum stops moving and hangs vertically at a standstill at position B.