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.
