Carla Mooney
Illustrated by Alexis Cornell
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Contents
Timeline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi Introduction
The World Runs on Science. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Chapter 1
Forces of Skateboarding.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Chapter 2
Motion and Energy of Snowboarding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Chapter 3
Spring of a Trampoline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Chapter 4
Form a Band: Waves of Sound and Light. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Chapter 5
Video Game Sparks: Electricity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Glossary Metric Conversions Resources Selected Bibliography Index
TIMELINE Third Century BCE: Greek astronomer Aristarchus suggests that the sun, not the earth, is the center of the solar system. 1512: P olish astronomer Nicholas Copernicus presents his heliocentric theory, which places the sun at the center of the solar system. He proposes that the earth travels around the sun once a year and rotates daily on its axis. 1609: I talian mathematician and physicist Galileo Galilei builds a powerful telescope that is able to see the moons orbiting Jupiter and sunspots on the sun. 1613: G alileo first describes the principle of inertia. 1668: E nglish mathematician John Wallis presents the law of conservation of momentum. 1675: E nglish physicist Sir Isaac Newton argues that light is composed of particles. 1687: N ewton publishes his laws of motion and law of universal gravitation. 1752: A merican philosopher and scientist Benjamin Franklin performs his famous kite and key experiment, which demonstrates that lightning is actually a form of electricity. 1800: I talian physicist Alessandro Volta invents the electric battery, which provides the first source of continuous current. 1801: E nglish scientist Thomas Young demonstrates the interference of light and concludes that light is made of waves. 1826: G erman physicist and mathematician George Ohm presents the law of electrical resistance. 1888: G erman physicist Heinrich Hertz proves the existence of electromagnetic waves. 1895: G erman mechanical engineer and physicist Wilhelm Conrad Rontgen discovers X-rays.
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THE PHYSICS OF FUN | TIMELINE
TIMELINE 1897: B ritish physicist Joseph John Thomson discovers the electron, the first subatomic particle. 1900: G erman physicist Max Planck develops his quantum theory of energy. 1905: G erman physicist Albert Einstein publishes his theory of relativity and ideas about light and the universe. 1915: E instein includes a description of gravity in his theory of relativity. 1934: G eorge Nissen and Larry Griswold build the first modern trampoline at the University of Iowa. Early 1950s: Surfers in California create the first skateboards using wooden boards and rollerskate wheels. 1958: A merican physicist Charles Townes invents the laser. 1981: The first national snowboarding competition is held at Ski Cooper in Leadville, Colorado. 1995: R esearchers from ETH Zurich in Switzerland and the University of Tokyo in Japan demonstrate quantum teleportation, a technique for transferring quantum information from one location to a receiver in another location. 1997: A n international team of scientists finds evidence of an anti-gravity force that is causing the universe to expand at an accelerating rate. 1998: S nowboarding makes its Olympic debut in Nagano, Japan. 2012: S cientists at CERN, a particle physics lab near Geneva, Switzerland, make the first discovery of a Higgs boson particle. 2016: S cientists prove the existence of gravitational waves, which are ripples in space-time that come from objects moving throughout the universe.
TIMELINE
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Introduction
The World Runs on Science
Why is physics a fundamental science?
Physics is part of everything! Biology, chemistry, meteorology, astronomy—every other science relies on the basics of physics.
What do you do for fun? Maybe you like to ride a skateboard, jump on a trampoline, or play the latest video games. Have you ever wondered how you can stay on top of the skateboard without falling off? Or why you can jump three times as high from a trampoline as from the ground? Or how video games are powered? All of these questions can be explained by physics! Many people do not think “fun” and “physics” go together. When they think of physics, they imagine complicated equations and laboratory experiments. In reality, physics doesn’t just happen in a lab. Physics is all around us. Every time you move, you are using physics. Do you play basketball? You’re using physics every time you step on the court to shoot a free throw. Do you like hockey? Physics is part of every shot and save on the ice.
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THE PHYSICS OF FUN | INTRODUCTION
Credit: SamuelSchultzbergBagge (CC BY 2.0)
In fact, physics is part of everything you do, from walking the dog to sledding down a hill to playing the guitar. Learning physics can help us understand the world around us and how it works.
WHAT IS PHYSICS? Physics is the study of matter and its motion and energy. Matter is anything that has mass and takes up space. Matter is all around you—including your own body! This book is made of matter. Your skateboard is made of matter. The air you breathe, the water you drink, and the food you eat are made of matter.
Before scientists better understood physics, most people assumed that nature was controlled by a supernatural or religious source.
Everything on Earth, in the solar system, and in the universe is made of matter.
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Scientists who study physics, called physicists, seek to understand how matter and the natural universe work. In fact, the word physics comes from a Greek word that means “nature.” Physicists analyze and explain the world’s natural phenomena, which are things that are observed or perceived. They perform and repeat experiments to study scientific laws, which are statements that describe how the natural world works.
Energy is the ability to do work, such as pushing an object up a hill or plucking a guitar string.
These scientific laws, such as the laws of gravity and Newton’s laws of motion, have been tested so much that scientists accept them as scientific truths. Physicists use these scientific laws to predict how other things will behave. Physics is a physical science. It is also known as the fundamental science, because it forms a basis for all other sciences, including chemistry, biology, and astronomy.
Without physics, the chemists, biologists, and astronomers would not be able to do their work! Physics has helped us better understand and predict natural phenomena in the world around us. Because of physics, we can explain why the sky is blue and a rose is red. We understand weather and know how to predict it, to a certain extent. We have learned how to predict and prepare for natural disasters such as earthquakes, hurricanes, and tornadoes. We can use our knowledge about what happens in a collision to design safety equipment to reduce damage. We can even predict what happens if you shoot a free throw, hit a baseball, or skate across a frozen pond. All because of physics!
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AN ANCIENT AND MODERN SCIENCE People have been studying physics for centuries. The ancient Greeks are considered to be the founders of early physics. Great thinkers such as Socrates (circa 470–399 BCE), Plato (circa 428–348 BCE), and Aristotle (384–322 BCE) pushed to better understand the natural world around them. They tried to explain what matter is made of and how it moves.
They observed the world and developed explanations for what they observed.
Quantum physics is the study of the microscopic world and its particles. This branch of physics has led to the development of the laser, the internet, modern electronics, and more.
Many years later, during the 1500s and 1600s, scientists such as Nicolaus Copernicus (1473–1543), Galileo Galilei (1564–1642), and Sir Isaac Newton (1643–1727) devoted their lives to the study of physics. They made lots of important discoveries about the natural world, many of which formed the foundation of modern physics today. Copernicus demonstrated that the earth orbits the sun. Galileo described many fundamental physics concepts and tested his ideas about motion. Galileo and his telescope. Some of his astronomical discoveries are shown in the sky. The World Runs on Science
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Primary sources come from people who were eyewitnesses to events. They might write about the event, take videos, post messages to social media, or record the sound of an event. For example, the photographs in this book are primary sources, taken at the time of the event. Paintings of events are usually not primary sources, since they were often painted long after the event took place. They are secondary sources. Why do you think primary sources are important?
Galileo also greatly improved the design of the telescope, which allowed scientists to make many new astronomical discoveries. Galileo lived during a period known as the Scientific Revolution, which lasted from about 1550 to 1700, when a series of discoveries in mathematics, physics, astronomy, biology, and chemistry caused whole societies to think differently about the nature of the universe. Other scientists during the Scientific Revolution performed experiments to prove Galileo’s ideas. Sir Isaac Newton developed his own three laws of motion and the law of universal gravitation. According to Newton’s law of gravity, every object with mass in the universe is attracted to every other object with mass.
FLIP FACT Nuclear physics is the study of the atom’s center, the nucleus. This branch of physics has led to important discoveries in medicine, energy, and the environment.
This attraction between objects is called gravity. How strong or weak that pull of gravity is depends on the mass of the objects and how close they are to each other.
After Newton, other scientists made discoveries about light, heat, radiation, electromagnetics, and other forces. During the nineteenth and twentieth centuries, some scientists studied the physics of very tiny particles of matter and energy, down to the subatomic level.
The study of physics is the science of how matter and energy interact and work together, no matter how large or small the size of an object.
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Without physics, many of today’s technologies would not be possible. The study of physics made it possible to develop lasers, televisions, radios, computers, smartphones, and more. Today, scientists are using physics to improve our daily lives further as they work on new technologies, ideas, and products. Physicists strive to develop and improve products and manufacturing processes in industries such as healthcare, energy, transportation, defense, manufacturing, and telecommunications. Physicists are also working with energy companies to develop new and efficient energy systems to harness Earth’s sustainable energy. Some physicists focus on studying the earth and weather, while others are making discoveries in space and astronomy. What does all this have to do with fun? Well, everything around you is made of matter. Physics explains what happens when matter is in motion. Every time you move, jump, or blow into a trumpet, you are using physics! The activities in this book will introduce you to the concepts that are used to explain the energy and motion of matter. We’ll take a look at skateboarding, snowboarding, trampolining, playing an instrument, and more to discover how the laws of physics make it possible to do all of these fun activities.
SCIENTIFIC METHOD The scientific method is the process scientists use to ask questions and find answers. Keep a science journal to record your methods and observations during all the activities in this book. You can use a scientific method worksheet to keep your ideas and observations organized. Question: What are we trying to find out? What problem are we trying to solve? Research: What is already known about this topic? Hypothesis: What do we think the answer will be? Equipment: What supplies are we using? Method: What procedure are we following? Results: What happened and why?
Ready? Let’s go!
KEY QUESTIONS • How has physics improved your life?
TEXT TO WORLD Think of three things you do for fun that involve physics. How do you know?
• Why does the study of physics affect so many other fields of science? The World Runs on Science
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Inquire & Investigate
VOCAB LAB Write down what you think each word means. What root words can you find to help you? Carla Mooney What does the context Illustrated by Alexis Cornell of the word tell you? energy, friction, fundamental science, gravity, matter, and physics. Compare your definitions with those of your friends or classmates. Did you all come up with the same meanings? Turn to the text and glossary if you need help.
EXPLORE FRICTION ON A RAMP One part of physics that affects everything you do is friction! Friction is a force that occurs when two surfaces rub against each other. Smoother surfaces generate less friction, while rough or bumpy surfaces generate more friction. Check it out!
• Create a ramp with stacked books and plywood or cardboard. Make sure there is empty space at the end of the ramp. • Starting with the smooth plywood or cardboard, release a toy car from the top of the ramp. Measure how far the car travels from the top of the ramp to where it stops. Record the results in your science notebook. Repeat two more times, and, using the three distances, calculate the average distance traveled by adding up all of the distances and dividing that number by the number of runs you did. • Place something bumpy, such as sandpaper or a towel, on the ramp’s surface. Tape it down so it doesn’t move. Repeat running the car down the ramp over the test surface three times and find the average distance. • Repeat this process for more test materials, such as carpet pieces or clothing. Calculate the average distance traveled for each material.
To investigate more, experiment with different objects sliding down the ramp. What happens? What conclusions can you make?
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• Compare your results. How did the car travel on each surface? On which surfaces did it travel farther? On which surfaces did it travel less? Based on your experiment, what did you learn about the friction of the different test surfaces?
THE PHYSICS OF FUN | INTRODUCTION