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Machines at Work and Play USING INFORMATIONAL TEXTS
Help students access a range of text types focused on science. Good readers are active readers, engaging in a productive struggle as they read. Readers also will improve their comprehension and be able to better analyze science content if they read the text more than once. Help students be active readers by providing appropriate close reading strategies and text-based questions as they read and reread a passage. Such questioning engages students’ interpretive processes while promoting attentive reading and thinking.
Machines at Work and Play
Using this Instructional Guide
Support Reading for Pleasure Encourage
• A ssign the Reader that best matches an individual student’s reading level. The lozenge on the back of the Reader reflects Lexile Measures.
students to share their impressions and opinions about the articles in the Reader. Use prompts such as the following.
BLUE
900–1050
RED
600–750
PURPLE
750–900
YELLOW
450–600
• I would read a book like this on my own time because… • I was surprised when I read _____ because…
• R efresh your science background on the topics as needed by reading the Content Refresher.
• I would like to revise the article _____. I could improve it by…
• Build on the instructional strategies included in this guide, or utilize your own favorite close reading strategies and instructional practices to help students analyze and interpret the expository text structures of the articles. These are argument, cause and effect, compare and contrast, description, sequence, and problem and solution. Direct students to the example graphic organizers on the Reader’s inside back cover.
• I most enjoyed reading about _____ because…
• Encourage students to keep a Science Notebook in which they answer the guiding question listed at the beginning of the article and their responses to the prompt at the end of the article, along with responses to additional prompts or observations, or feelings of their own related to the topics of the article.
• I really liked the picture on page _____ because… • I would like to know more about…
Engage with Informational Text Encourage students to preview each article before reading, recall details and make inferences during reading, and draw conclusions after reading. Use the questions included for before, during, and after reading for each article, or adapt your own. onsider doing a think-aloud to model engaging with C the text. Choose a paragraph or section of text and use the questions provided or your own to model previewing, recalling details and making inferences, and drawing conclusions afterward.
LEVELED READERS INSTRUCTIONAL GUIDE
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Find Cause-and-Effect Signal Words
FORCES AT WORK Pages 2–3 Overview: The article introduces the scientific concept of work and its relationship to force and distance. Work is accomplished on an object when a force acting on an object makes it move.
Activate Prior Knowledge Introduce the word work. Ask students to consider what the word means in their everyday lives. Allow time for students to think, and then have them write down as many real-life examples of people doing work as they can. USE NOTEBOOKS What I Think, Page 6 Students may print this page and tape it into their notebooks or draw a table on their own paper. Before Reading What do you think force means? What is work? Write a definition of each term in your own words.
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Reading Detectives Have students read the article independently, paying particular attention to the vocabulary words. After reading, have students share what they have learned about the terms. USE NOTEBOOKS Describe Force and Work, Page 8 Students may to print this page and tape it into their notebooks or answer the questions on their own paper. During Reading How is force related to how heavy an object is? How do you use math to figure out the amount of work done?
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Explaining Concepts Point to the introduction to “Forces at Work.” Guide students to relate each example to what they learned about forces in the text. Encourage students to find details in their own readers to support their answers. For example, ASK: • What force causes a ball to fly through the air? The push of the legs of the person who is kicking it. • What forces cause a swing to move back and forth? Gravity and often a push.
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SCIENCEFLEX MACHINES AT WORK AND PLAY
Direct students to the introduction or one of the first three paragraphs of “Forces at Work.” Instruct them to identify at least one cause-and-effect relationship in their assigned paragraph. With students, make a list of some words that signal cause and effect, such as cause, because, and as a result. Tell students that sentence structures such as If… then and When… can also show cause and effect relationships.
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After Reading How are the scientific meanings of force and work different from the definitions you wrote? USE NOTEBOOKS On Their Own Before students go outside to play, remind them about this article. Encourage them to think about the “work” they will be doing. Then, have them write about it in their notebooks.
THE PROBLEM OF THE PYRAMIDS Pages 4–7 Overview: The article introduces simple machines through the problem of building the pyramids and one way ancient Egyptians might have solved that problem—by using a simple machine, the inclined plane.
Build Background Explain that a machine is any tool or device that makes work easier. Write or say the word machine and elicit examples. Now contrast that term with simple machine, which is a machine with few or no moving parts. Tell students that if they have ever pulled a wagon, pushed a shopping cart, turned a doorknob, or even used a spatula, they have used a simple machine. An inclined plane is a ramp.
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Before Reading What do you know about the pyramids?
Preview Visuals Draw students’ attention to the
Writing Opinions Ask students to imagine that
photograph of the Great Pyramid. ASK:
they are living in Egypt 4,000 years ago. The Pharaoh has ordered pyramids to be built, but the builders are having trouble moving and lifting the stones. Have them write a persuasive letter to the head builder, explaining how an inclined plane could help make the work easier. Students should state their opinion clearly, support it with reasons and facts, and write a strong conclusion.
• H ow would you describe the shape of this structure? Some students may know it is a pyramid. Explain or remind students that a pyramid is a triangular prism. Explain that the pyramid in the photo has a square base, but other pyramids may have triangular or even fived-sided bases. Point out the sloping sides of the Great Pyramid. • W here would you go to visit the Great Pyramid? Some students may know that the Great Pyramid is in Egypt. Point out the locator globe in the article and locate Egypt on a world map. • How do you think people built the Egyptian pyramids? Did they use machines? Some students may suggest that the Egyptians built the pyramids by hand, while others may suggest that they used bulldozers and trucks. Have students read the complete article independently to see if their predictions are correct.
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During Reading What does the article tell you about machines? How might the Egyptians have used inclined planes?
Check and Confirm Predictions Guide students to recall details from the text and diagrams to check their predictions. For example, details about the size and weight of the stones suggest that the pyramids were not built by hand. And the Egyptians could not have used bulldozers and trucks, because the Great Pyramid of Giza has been standing for 4,000 years— long before people learned how to build gasolinepowered engines or use electricity. Have students use the diagrams and the captions to summarize how the pyramids may have been built. USE NOTEBOOKS Solving the Problem of the Pyramids, Page 14 Students may print this page and tape it into their notebooks or answer the questions on their own paper.
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After Reading What questions does the article leave you wondering about?
USE NOTEBOOKS On Their Own Have students research another simple machine based on inclined planes—the wedge. They should draw pictures of them and explain how they make work easier.
ARCHIMEDES’S SOLUTION Pages 8–11 Overview: The article describes Archimedes’s invention of a simple machine known as a water screw, which is the same basic structure as screws and nuts and bolts used today.
Make a Model ASK: What do you think would happen if you twisted an inclined plane around a rod? Accept all answers. Cut a triangle from a sheet of paper with one side the same length as a pencil. Give students time to observe the triangle. Instruct them to color the long edge (hypotenuse). Have students tape one side of the triangle to the pencil and wind it around. USE NOTEBOOKS Make a Model of a Simple Machine, Page 20 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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Before Reading Which pictures show images from history? Which picture shows something we use today? Where have you seen objects like this before?
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Read-Discuss-Share Have students read through the article independently. Next, have students share what they recall, focusing their discussion on the questions in their Science Notebooks. Encourage students to add more details or ask questions to clarify information. Finally, have students reread the article and make any necessary changes to their notes. USE NOTEBOOKS Archimede’s Screw, Page 25 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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During Reading What was Archimedes’s problem? How did he solve it? What is a screw?
Compare and Contrast Texts Guide students to compare and contrast the first three pages of the text with the final section. ASK: • Which part of the text has verbs in the past tense? The first part. • What is the purpose of this part? To tell the history of Archimedes’s discovery. • Which part of the text has verbs in the present tense? The second part. • What is the purpose of this part? To explain the science behind the story. Discuss the idea that it is valuable to have both types of information—the historical narrative and the scientific explanation—in order to fully understand Archimedes’s work. ASK: Is Archimedes’s machine a screw? How do you know? Listen for answers about how it is structured.
Develop Concepts Use these prompts to lead a discussion about the structure and function of screws. • Two ways that a screw makes work easier are… Students should state that a screw changes the direction of a force. Like an inclined plane, a screw reduces the amount of force needed to do a task by increasing the distance over which the force is applied. • Threads help a screw by… increasing the distance over which force is applied, making it easier to attach a screw. Explain that the threads also help the screw “grab” the wood, pulling the screw down into the wood. Once a screw is inserted, the threads hold the wood and the screw in place.
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After Reading Why does a screw take less force to use than a nail? Why do some screws have more threads and others fewer? USE NOTEBOOKS On Their Own With the help of an adult, have students find a nail and a screw that are about the same diameter. Then, using the appropriate equipment—a hammer and a screw driver —insert them into a piece of soft wood. Students shouldthen write a few sentences comparing the experience.
THE RIGHT LEVER FOR THE JOB Pages 12–13 Overview: The article compares and contrasts the structure and function of the three classes of levers, another simple machine.
Access Prior Knowledge Have students look at the picture of two children sitting on a seesaw on page 12 of the Reader. Tell students that although the children on the seesaw are playing, they are also doing work. Review the definition of work students learned in the first article. Then challenge students to identify the forces children are using to make the seesaw move. ASK: How do the children sitting on the ends of a seesaw move? They take turns pushing down on the ground with their legs. Guide students to see that when one child pushes down on the ground, he or she moves up, while the other child moves down. Before Reading What other examples of levers do you see in the pictures? Have you ever used any of these tools?
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Text Feature Walk-Through Have students preview the pictures and headings. Tell students that text features like the title, headings, pictures, captions, labels, and even colors can help readers understand a text. ASK:
• Which word in the title is in a different color? Lever. • Why do you think that is? It is the most important word in the title, because it is the main topic of the article. Have students identify the three section headings and use the colors to identify the pictures that are examples of each. Direct students to point to the labels in the pictures. ASK: • How are the three kinds of levers similar? They have the same parts: an arm, a fulcrum, a load, and an effort force. • How does the author help readers identify examples of each kind of lever? By listing them in a separate section labeled “Examples” and putting them in bold print. USE NOTEBOOKS Use Text Features, Page 33 Students may print this page and tape it into their notebooks or answer the questions on their own paper.
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During Reading What are the parts of a lever? How are the three classes of levers different?
Compare and Contrast Have students read the article independently. When they finish, have students turn to a partner and discuss what they learned. USE NOTEBOOKS Compare Three Classes of Levers, Page 34 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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After Reading Look at the picture next to the title. What kind of lever is it? What are the parts? How do you use it? How does it make work easier? USE NOTEBOOKS On Their Own Encourage students to research levers in their own bodies. They might make labeled drawings of a first-class lever (the point where the skull attaches to the vertebral column), a second-class lever (the toes supporting the body when on tiptoe), and a third-class lever (the forearm lifting a load).
THE SCIENCE BEHIND CURLING Pages 14–17 Overview: The article showcases causes and effects in the sport of curling and describes how friction is a force that resists the movement of something across a surface.
Elicit Ideas Ask students to vigorously rub their palms together for 10–15 seconds. Have them observe what happens. Remind them that observations may include any sounds they hear and what they feel with their sense of touch. Tell students to dip their fingers into some liquid detergent and spread a generous amount on the palms of their hands. Then have them rub their hands together as they did before. USE NOTEBOOKS What I Think, Page 38 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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Before Reading Based on the pictures, how do you think curling is played? What questions would you like to ask the author about this sport?
Interactive Read-Aloud Read the article aloud, including the captions as you come to them. As you read the first two paragraphs, have students close their eyes and visualize what is happening. Use questions like the following to guide discussion about key ideas. ASK: • How does the lead move the stone? Have students both describe and demonstrate the motions and describe them using precise language from the text (pushes off, slides, releases, etc.). • Where did curling get its name? The stone moves in a curved path. • What are the two other roles in curling? What do they do? Sweepers sweep the ice in front of the stone. A skip shouts directions. • What are the sweepers trying to do? They are trying to guide the stone to its target by melting the ice in front of the stone to reduce the friction. • How can the sweepers make the stone travel farther and straighter? By sweeping in front of it. LEVELED READERS INSTRUCTIONAL GUIDE
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• How can they make it curl differently? By sweeping faster or slower. • What are some ways friction is reduced in curling? The stone has a concave bottom (one that is curved inward), so less of it touches the ice. The ice is sprayed with a mist of water, producing “pebbles” on the surface that melt into a thin film as the stone touches them. The sweepers brush the ice, raising the temperature and causing it to melt more. • What causes the stone to finally stop? The movement of the stone can no longer overcome the friction between the stone and the ice. During Reading What does friction have to do with curling? What is unique about the curling stone, curling ice, and the sweepers’ brooms?
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Reading Detectives Instruct students to reread the last two pages of the article, looking for statements that tell how one thing affects another. Allow students time to read independently. Then have them share the cause-and-effect relationships they found. USE NOTEBOOKS Describe Cause and Effect, Page 40 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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After Reading What does it mean that “curling requires skill and a good understanding of science”? Use details from the text to support your explanation. USE NOTEBOOKS On Their Own Suggest students to write about or draw pictures to explain the role of friction and lubrication in everyday activities. Then, encourage them to use simple props to demonstrate them. Encourage the use of humor.
FLYING ON WHEELS Pages 18–21 Overview: The article explains how a simple machine called a wheel and axle makes work easier in everyday objects such as skateboards, steering wheels, faucet handles, and doorknobs.
Introduce Concepts ASK: What is a wheel? Students are likely to describe a wheel as a round object that rolls, such as the wheels of a bicycle or car. Define a wheel as any circular object that turns around a center point, or axis. A wheel may be spherical, like a ball, or cylindrical, like a dowel, or the wheels of a car. A wheel may be solid or hollow. Wheels reduce the frictionbetween an object and the surface over which it moves, so less force is needed to move the object. Explain that scientists do not classify a wheel as a simple machine because a wheel does not change the amount of force applied to an object or the direction of the force. But when a wheel is attached to a rod or shaft, the result is a simple machine called a wheel and axle. Tell students that an axle is a rod that is inserted into the middle of a wheel.
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Before Reading What activity is the girl doing in the picture on pages 18 and 19? How do you think the wheels on her skateboard help her move?
Identify Author’s Point of View Have students read the title and the text and caption on pages 18 and 19 of the Reader. ASK: • How do you think the author feels about Minna’s skateboarding? Students should notice that the author uses words like “fearless” and “rising star” to show that Minna’s skills and accomplishments are impressive. • Do you agree with the author’s point of view? Why or why not?
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During Reading Can you find a wheel and axle in each picture on pages 20 and 21? Do any of them surprise you? Why?
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Read for Details Have students read the rest of
Build Background Tell the class that a pulley is the
the article independently. Then guide them to reread certain paragraphs in the article to help them answer the questions that follow. 1. How does a wheel and axle transfer force? (paragraphs 5 and 6) 2. How can you identify a wheel and axle that does not have a round wheel? (paragraph 7) 3. How does a wheel and axle reduce the amount of force needed to move an object? (paragraphs 8 and 9) 4. How can a wheel and axle increase the distance an object travels? (paragraph 10)
sixth kind of simple machine. Pulleys are used to make it easier and safer to move objects. There are two kinds of pulleys—fixed pulleys and movable pulleys. Explain that fixed pulleys are attached to a single location—they are fixed in place. In contrast, movable pulleys slide along a rope that is attached to a ceiling or another stationary object.
USE NOTEBOOKS Describe Cause and Effect, Page 44 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
Paraphrase Have students choose one picture from “Flying on Wheels,” identify the wheel and axle(s), and explain in their own words how it makes work easier. Encourage them to find details in the text that support the explanation.
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After Reading What is the main idea of this article? What are some key details that support it? USE NOTEBOOKS On Their Own With adult supervision, encourage students to examine an everyday wheel and axle, such as the steering wheel of a car, a doorknob, screwdriver, or rolling pin. Have them sketch the machine in their Science Notebook and draw arrows to show how each part moves.
PULL IT UP! Pages 22–23 Overview: The article compares and contrasts types of pulleys and explains how the sixth kind of simple machine can be used in combinations.
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Before Reading What types of pulleys can you learn about from this article?
Preview Visuals Have students preview the title and the photograph. ASK: • Where are these people? On a skyscraper • What is their job? Window washers • Where do they need to go? Up the side of the building all the way to the top • How can they get there? By pulling down on the ropes to pull themselves up Discuss what students think about this job and whether they would enjoy doing it. Then encourage them to read aloud the introductory text on page 22.
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During Reading How do the diagrams help you to better understand the content in this text? What makes pulleys so useful?
Compare and Contrast Instruct students to reread the text that accompanies the diagrams on page 23 of the Reader. Encourage them to make connections between the diagrams and the text—for example, finding information about the direction of the force in both. Then, have them identify which statements are true for fixed pulleys, which are true for movable pulleys, and which are true for both kinds of pulleys. USE NOTEBOOKS Compare Fixed and Movable Pulleys, Page 53 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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After Reading What kind(s) of pulley(s) do you think the window washers in the photograph are using? Why? LEVELED READERS INSTRUCTIONAL GUIDE
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USE NOTEBOOKS On Their Own Ask students to write a short story about one of the following situations. • A sailor wants to fly a flag from the top of a tall mast • A construction worker needs to lift heavy steel beams to the top of a new building. • A family wants to save energy by hanging their clothes in the sun. A clothesline stretches from a deck to a pole in the yard. The family needs to be able to move the clothes back and forth between the deck and the pole. Students can write from a first-person point of view, as if they were one of the sailors, construction workers, or family members, or from a third-person point of view, as a narrator outside the story. Challenge students to create realistic characters by describing their actions, thoughts, and feelings and by including dialogue. Their stories should also clearly show how the pulley solves the characters’ problem.
THE BICYCLE: A NOT-SOSIMPLE MACHINE Pages 24–25 Overview: The article describes describes parts of a bicycle to show how compound machines are made up of simple machines.
Elicit Ideas Tell students that a bicycle is composed of a number of simple machines that work together to make it function. Spark thinking about what happens when riding a bike. ASK: • How do you make a bike move?
paragraph that introduces the article. Direct students’ attention to the large infographic. Guide students to see that the line from each caption leads to the part of the bike that the caption describes. Challenge students to study the infographic, close the Reader, and do the matching. Then they can open the Reader again and check their answers. USE NOTEBOOKS Bicycle Parts, Page 60 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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During Reading Name each kind of simple machine found in a bicycle. What job does each do in a bicycle?
Synthesize Information Instruct students to prepare Venn diagrams that compare and contrast the characteristics of simple and compound machines. Then have students write a compare-and-contrast paragraph based on their Venn diagram, including any examples they listed. Remind students to use phrases such as for example and for instance to introduce examples.
Explain Ideas Have students reread the article independently, and then read the “Riding on Hills” section aloud. Have students draw a diagram of the information in their Science Notebook and use it to explain the text in their own words. USE NOTEBOOKS Compare Simple and Compound Machines, Pages 63–64 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
• How do you stop a bike? USE NOTEBOOKS What I Think, Page 57 Students may to print this page and tape it into their notebooks or answer the questions on their own paper. Before Reading What is this article about? Why do you think a bicycle might be “a not-so-simple machine”?
USE NOTEBOOKS On Their Own With adult supervision, encourage students to examine everyday compound machines, such as scissors, a stapler, a can opener, and a wheel barrow. Have them sketch a machine in their Science Notebook and label the simple machines in it.
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SCIENCEFLEX MACHINES AT WORK AND PLAY
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After Reading How do simple machines work together to help you ride a bike?
• How do you turn a bike?
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Text Feature Walk-Through Read aloud the
REINVENTING SOME WHEELS Pages 26–29 Overview: The article presents a time line of advances in bicycle technology from the early 1800s to today.
Build Background Elicit students’ ideas about the meaning of the word technology. Many students are likely to state that it refers to electronic devices, such as computers and GPS devices. Then direct students to the article. Have them scan the introductory text, to find the sentence containing the word technology in bold print. Have them read the surrounding paragraph and skim the descriptions in the timeline to deduce that technology refers to more than just electronic equipment. Guide them to understand that technology is the use of scientific knowledge for practical purposes, such as the development of machines and other products to meet various human needs.
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Before Reading How is the article organized? What years does it cover? What is the article about?
Text Feature Walk-Through Read aloud the introduction to the time line in “Reinventing Some Wheels.” Guide students to notice how the text and illustrations are arranged across the pages, and have them use the line at the bottom and the years to follow the events in chronological order. Elicit or explain that this time line shows some key developments in the history of bicycle technology. ASK: • What is the earliest kind of bicycle shown on this time line? The running machine, in 1817 • What are the most recent kinds of cycles shown on the time line? Recumbent bicycles and hand cycles , in the 2000s Tell students to read each entry on the time line, looking for information about how each new kind of bicycle was safer, more comfortable, or more useful than earlier bicycles. Encourage students to share at least one piece of information that was new to them.
USE NOTEBOOKS Building Better Bikes, Page 61 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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During Reading How do the pictures help you understand the text? What details do you learn from the pictures that you might not know from just reading the text?
Compare and Contrast Texts Have students compare and contrast the information about bicycles in “The Bicycle: A Not-So-Simple Machine” and “Reinventing Some Wheels,” on pages 24–29 of the Reader. After students have responded to the Science Notebook page, discuss the types of information each text provides. Discuss the answers as a class, and point out that students can follow a similar approach when looking for appropriate sources for their own research. Challenge students to think of a topic that would require information from both of these texts (for example, simple machines used in hand cycles). USE NOTEBOOKS Compare Text Types, Page 62 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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After Reading Based on the information in “Reinventing Some Wheels,” what conclusions can you draw about how bicycles have changed over time? USE NOTEBOOKS On Their Own Encourage students to conduct research to learn about technological innovations in racing bicycles used in professional road races such as the Tour de France. Such innovations include ultralight bikes, aero bikes, and electronic components. Have students prepare a time line to summarize what they learn. Entries should focus on changes since the 1960s and should include explanations of how each innovation helps a bike racer compete. Tell students to check that they have presented the innovations in chronological order. Encourage students to add relevant visuals, such as photos, illustrations, and diagrams.
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THE ENGINEER OF PLAYGROUND PIZAZZ Pages 30–35 Overview: The article introduces engineering design processes through a profile of Peter Hueken, a playground designer who creates playgrounds made mostly of wood and other natural materials.
Elicit Ideas ASK: What is an engineer? Accept responses that allude to someone who designs new products or technologies. Follow up by explaining that an engineer is a person who uses science and mathematics to design objects or systems that solve problems or meet human needs. Have students imagine that they are part of an engineering team that has been asked to design a new piece of playground equipment. ASK: How would you go about designing the new equipment? What would you need to know? What steps would you take? Encourage students to share their ideas about what the engineers would need to know and what kinds of things they would do in order to develop a good design. USE NOTEBOOKS Imagine, Page 65 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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Before Reading What do the pictures in the article show? What do you think the article will be about?
Analyze Text Have students read the complete article independently. Encourage them to think about how Mr. Heuken goes about designing playground equipment. Then have students do a close read, usingthe Science Notebook questions as a guide. At the end, ASK: What are some of the things that Mr. Heuken’s design team does as they plan playground equipment? They make detailed drawings and threedimensional models. Guide students to see that these drawings and models need to be adjusted as the team works on their plan. These revisions improve the design of the playground equipment.
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USE NOTEBOOKS Analyze Text, Pages 66–67 Students may to print this page and tape it into their notebooks or answer the questions on their own paper.
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During Reading According to Mr. Heuken, what makes a good play space? What process does he follow to design it?
Apply Concepts Discuss with students that models can take different forms—2D drawings, software programs and simulations, 3D printed examples, and other physical models. Models can also represent one aspect of the solution or be a fully functional replica. Models can be life-size, or smaller or larger than the real thing. Explain that engineers sometimes make a full-size model, called a prototype. For example, engineers would make and test a prototype of a new kind of bicycle before sending the design to a factory. However, it is more practical to make a model of a playground that is much smaller than the real thing. Direct students to the model shown on pages 32–33. ASK: • Where in the text does it tell what the model is of? The last sentence or two on page 33. Note that the model is not identified in the caption; students need to find this information in the text. • How useful do you think this model was to the team? Answers will vary. Look for analysis statements of the purpose and features of the model.
Draw Conclusions Read the complete analogy Mr. Heuken makes on page 33: “Nobody uses a car because it has brakes… Nobody goes to a playground because it is safe.” Discuss how this analogy relates to Mr. Heuken’s goal. ASK: • What is Mr. Heuken’s goal when he designs a playground? Guide students to state that his goal is to make a playground that is both safe and exciting for children. • What does he mean when he says “Nobody uses a car because it has brakes… Nobody goes to a playground because it is safe”? A playground needs to be safe, but no one will use it unless it is also fun.
• What are some of the things that limit his designs? The playground equipment needs to be safe, and it needs to fit into the site available.
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After Reading What other questions would you like to ask Mr. Heuken about designing playgrounds? USE NOTEBOOKS On Their Own Instruct students to think about the playground equipment at school or in their neighborhood. In their Science Notebooks, have them name equipment and describe any simple machines it uses. Then have them think about how they might redesign the equipment to be more fun, while remaining safe. Encourage students to draw their ideas and add captions to explain them.
SYNTHESIZE INFORMATIONAL TEXT Page 36 Overview: These activities elicit connections among the concepts of the articles included in this Reader.
Connect Concepts Guide students to discuss the relationships among the articles implied by the word web displayed on the last page. Encourage students to create other word web visualizations of relationships among the articles. They might focus on a subset of articles in order to add more detail. Have students draw their new word webs into their Science Notebooks. USE NOTEBOOKS What I Think, Pages 73–75 Students may print this page and tape it into their notebooks or answer the questions on their own paper.
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CONTENT REFRESHER Machines at Work and Play Simple machines seem to be as old as civilization itself. No doubt wedges were used in prehistoric times to split wood or stones. Early people also would have used levers for moving heavy stones or digging in the soil. It is known that levers were used in shadufs, a device for lifting water in Egypt and India as early as 1500 bce. By 3 bce, other simple machines, such as pulleys and screws, were commonplace for doing work.
LESSON 1
FORCE AND WORK Most of the activities we perform each day involve moving objects. A force–a push or a pull–must be applied to an object to set it in motion. Forces usually work in pairs. When a person walks, her or his feet push on the floor and the floor pushes back. A person applying a force on a small object can cause a lot of motion. The same person attempting to push a school bus might be unable to set it in motion. Forces cannot be seen but their effects can. Forces can also be measured. A spring scale measures the size of a force in a unit called a newton, so named because Sir Isaac Newton defined them when investigating gravity. The force of gravity pulls objects towards Earth’s center and is measured as weight. Work occurs when an object is moved. Whenever work takes place, energy is used. Energy is the ability to make things move or cause a change. W(ork) = F(orce) × d(istance). When work is measured, it determines the amount of energy being transferred. When force is measured in newtons and distance is measured in meters the resulting unit is called a joule after the physicist James Prescott Joule, who explored work in the 1800s. Lifting a heavier object, which requires a greater force, results in more work than lifting a lighter object. This relationship is also true of moving the same object longer or shorter distances.
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LESSON 2
INCLINED PLANES The inclined plane is unique among the six simple machines in that it does not move. An inclined plane is a type of simple machine that is commonly called a ramp. It consists of a flat surface that slants, or slopes. Inclined planes connect a lower elevation to a higher elevation. Objects are moved along an inclined plane in an effort to raise or lower them. The principle behind the inclined plane is simple: The amount of work performed by lifting an object a certain vertical distance is the same as that performed by moving the object the same vertical distance, but across the inclined plane. However, the object moved using an inclined plane moves a greater distance. The advantage resulting from using an inclined plane is that less force is needed because the object is moved over a greater distance. The input force used on an inclined plane is the force with which you push or pull the object up the ramp. The output force is the force needed to lift the object straight up. The output force is equal to the weight of the object. A person lacking the strength to lift a given object straight up can push it up a gently-sloped inclined plane if the force of friction between the ramp and the object can be overcome. Lesson 5 addresses friction as a force and ways it can be overcome. LESSON 3
WEDGES AND SCREWS A wedge is a simple machine often made of wood or metal that is thick at one end and narrows to a very thin edge at the other end. A wedge is a modified inclined plane. While the inclined plane requires less force when performing work by distributing the applied force over an increased distance, a wedge multiplies this advantage by including more than one inclined plane in its design.
Unlike an inclined plane, the wedge is not stationary, but moves in the direction of the applied force. What makes the wedge a simple machine is that applying a weak force to the thick edge of the wedge results in a strong force that pushes an object or objects apart. The thin edge of the wedge penetrates deeper with each application of force. Wedges can also be used to lift objects. Moving the wedge its entire length results in lifting the object only the thickness of the wedge. Screws make it easier to do work by changing the direction of an applied force and the distance over which the force is applied. During the manufacture of a screw, an inclined plane is tooled so that it spirals around and protrudes from the shaft of the screw. This feature is known as the screw’s threads. The number of threads on the screw’s shaft depends on the length and slope of the inclined plane wrapped around it. The shorter and steeper the slope, the fewer the number of threads on the shaft. There are several different types of screws, but all function in a similar manner. Machine screws have blunt tips. Their threads spiral the shaft’s entire length, meshing with the threads of other objects to draw them together. Screws used in wood have spiraling threads most of the way up the shaft. They are tapered to a point at the tip so that they are more easily drawn down into the wood when a screwdriver is turned. Screws are also useful for lifting objects and materials, such as water. LESSON 4
LEVERS All levers consist of four components: an arm (a beam or bar), a fulcrum (the pivot point), a load (the object to be moved), and an effort (the force required to move the load). Application of force to one part of a lever produces a useful action at another part of the lever. Most levers do work by reducing the amount of force required to lift an object or pry something loose, although some levers work by increasing the distance and speed at which an object is moved.
There are three types of levers: first-, second-, and third-class levers. One type of lever is not better than another. Each simply has the fulcrum in a different location. Examples of first-class levers include a catapult, scissors, and a boat’s oars. The loads in second-class levers move in the same direction as the effort. A nutcracker, a crowbar, and a wheelbarrow are all second-class levers. Third-class levers also move the load in the same direction as the effort. Examples are a broom, a stapler, and tweezers. In a first-class lever, pushing down on one end of the arm causes the other end to lift up, thereby changing the direction of the force. When the fulcrum is centered between the effort and load, as in a seesaw, an effort equal to the weight of the load will lift the load. Moving the fulcrum closer to the load reduces the amount of force required to lift the load. Moving a lever’s fulcrum closer to the load increases the distance that the effort end must move, while decreasing the distance that the load moves. LESSON 5
FRICTION Getting an object to move requires that a force be applied to the object. A moving object will not remain in motion forever, at least not within the bounds of Earth and its atmosphere. Other forces act on the object that will eventually cause it to slow down and stop. Gravity is one such force. Friction is another. Friction can also prevent an object from moving. Friction occurs when two objects rub against each other. No matter how smooth surfaces may appear, they contain tiny bumps and pits that cause objects to “catch” as they slide past one another. Such resistance slow objects down, generates heat and noise, and can cause the surfaces of objects to wear. Friction makes work harder by increasing the amount of force necessary to move an object and keep it in motion. The rougher a surface is the greater the friction produced. The greater the friction, the more force needed to move the object. If friction is stronger than the applied force, the object will not move. Friction also increases if two objects are pushed harder against each other.
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CONTENT REFRESHER One way of reducing friction is to place ball bearings between two objects. These smooth steel balls can roll between metal parts. Skateboards and bicycles use ball bearings to reduce friction. Objects moving through a gas or liquid encounter fluid friction. The force required to overcome fluid friction is usually significantly less than that needed to overcome the texture of solid surfaces. A fluid added between two solid surfaces keep them from making direct contact and reduces friction. Lubricants fulfill this role in many machines. LESSON 6
WHEEL AND AXLE One of the world’s most important inventions was the wheel. A wheel reduces the amount of friction between the surfaces of two objects as one passes by the other. Scientists do not classify a wheel as a simple machine because a wheel does not change the amount of force applied to an object or the direction of a force. Attaching a wheel to an axle creates a simple machine that transfers and modifies force. An axle is a shaft inserted into the center of a wheel. For each revolution of the axle, the wheel makes one complete revolution and vice versa. Because the axle and the wheel are of different diameters, however, force is modified as it moves from one to the other: The force is decreased when transferred from the axle to the wheel, and magnified when transferred from the wheel to the axle. The magnification of force that occurs when force is transferred from a wheel to an axle is what creates the mechanical advantage of this simple machine. Door knobs and screwdrivers are tools that make use of the mechanical advantage of a wheel and axle. Both receive a manually applied force at one end—the wheel end—and magnify the force at the other end— the axle end—to complete the task. A gear is a special wheel that has small, evenly spaced teeth around its outer edge. A system of gears is a device with toothed wheels that fit into one another. When gears of different sizes are connected, they function like a wheel and axle in that force is transferred from one to the other. When effort is
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applied to a gear (the driving gear), whose teeth mesh with another gear (the driven gear), force is transferred to the driven gear, causing it to turn. A driven gear turns in the opposite direction of the driving gear. Gear ratio is the ratio of the number of rotations of the driving gear to the driven gear. A gear ratio of 1:5 reflects a system in which a driving gear is five times the size of the driven gear. For every rotation of the driving gear, the driven gear rotates five times. LESSON 7
PULLEYS A pulley consists of a wheel that rotates freely around a stationary axle (as opposed to being attached to it like a wheel-and-axle system). The outer rim of a pulley is grooved to accommodate a rope or chain. Although single, stationary (fixed) pulleys do not magnify force, they are useful for lifting objects high overhead. By using a pulley, the direction of applied force can be reversed so that pulling down on the rope around a pulley raises an object attached to the other end of the rope. It is easier to pull down than to push up because your own weight and gravity help you (but it does not change the amount of force required). Theoretically, the force required to lift an object using a single pulley is identical to the force required to lift the object without using the pulley. Actual pulley systems may find an increase in the required force due to friction of the rope against the pulley. Pulleys are used to help us move objects more safely and easily. Some pulleys work by changing the direction of applied force. Others work by reducing the amount of force required to move a heavy object. A moveable pulley moves along the rope as the rope is pulled. In this system, one end of the rope is firmly attached to a stationary object, and the pulley is attached directly to the load. A movable pulley reduces the amount of force required to lift the load by half. That results because half of the weight of the load is supported by the stationary object and half is supported by the person pulling on the rope. The tradeoff is that the rope must be pulled twice as far in order to get the load to move half as far. Unlike a fixed pulley, a moveable pulley does not change the direction of the applied force.
LESSON 8
COMPOUND MACHINES Many devices found in everyday life do not resemble the six simple machines covered in the preceding lessons. More complex machines can be constructed by combining combinations of the six simple machines. These more complex devices are compound machines. Compound machines have moving parts. To understand the mechanical advantage of a compound machine, the mechanical advantage of each simple machine must be known. The overall mechanical advantage of the system is the product of the individual mechanical advantages of the simple machines it includes. Compound machines usually make work much easier. Imagine walking a ten-kilometer circuit of your local forest preserve. Now compare the effort required if you were to complete the same circuit on your mountain bike. The bicycle greatly reduces the effort required because it comprises three simple machines: wheel and axle, gears, and a lever. Compound machines help with work either by using less force over more distance or more force over less distance.
LESSON 9
ENGINEERING DESIGN Engineering is considered the application of science and mathematics to solve problems by developing technologies that are useful to people. The thought, planning, testing, and improvement involved in engineering are nothing new. Ancient Egyptians, Romans, Chinese, and others built engineering marvels such as pyramids, aqueducts, and grand canals. Today, the focus on STEM capitalizes on these same processes. Like scientific methods, there is no one engineering design process. The NGSS advocates for a generalized three-part process for problem solving. Students define a problem using criteria for success and constraints or limits of possible solutions. They then research and evaluate multiple possible solutions to a given problem. After testing, students optimize solutions by revising them to create the best possible solution given the criteria and constraints. This three-part process encompasses all aspects of other five-, six, and seven-part design cycles that delineate specific actions such as defining the problem, imagining and brainstorming, researching background, planning solutions, creating models or prototypes, testing possible solutions, and improving the most successful designs for an optimal solution.
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