chapter 5 resource: motion, forces, and simple · pdf fileany other reproduction, for use ......

Glencoe Science

Chapter Resources

Motion, Forces, and Simple Machines

Includes:

Reproducible Student Pages

ASSESSMENT

✔ Chapter Tests

✔ Chapter Review

HANDS-ON ACTIVITIES

✔ Lab Worksheets for each Student Edition Activity

✔ Laboratory Activities

✔ Foldables–Reading and Study Skills activity sheet

MEETING INDIVIDUAL NEEDS

✔ Directed Reading for Content Mastery

✔ Directed Reading for Content Mastery in Spanish

✔ Reinforcement

✔ Enrichment

✔ Note-taking Worksheets

TRANSPARENCY ACTIVITIES

✔ Section Focus Transparency Activities

✔ Teaching Transparency Activity

✔ Assessment Transparency Activity

Teacher Support and Planning

✔ Content Outline for Teaching

✔ Spanish Resources

✔ Teacher Guide and Answers

Glencoe Science

Photo CreditsSection Focus Transparency 1: UNIVERSAL PRESS SYNDICATESection Focus Transparency 2: G. Savage/Vandtstadt/Photo ResearchersSection Focus Transparency 3: Jeff Greenberg/Visuals UnlimitedTeaching Transparency: (t) Lew Long/The Stock Market, (cl) Bob Daemmrich, (cr) Bob Daemmrich,(b) Gregg Otto/Visuals Unlimited

Copyright © by The McGraw-Hill Companies, Inc. All rights reserved.Permission is granted to reproduce the material contained herein on the conditionthat such material be reproduced only for classroom use; be provided to students,teachers, and families without charge; and be used solely in conjunction with theMotion, Forces, and Simple Machines program. Any other reproduction, for useor sale, is prohibited without prior written permission of the publisher.

Send all inquiries to:Glencoe/McGraw-Hill8787 Orion Place Columbus, OH 43240-4027

ISBN 0-07-867198-1

Printed in the United States of America.

1 2 3 4 5 6 7 8 9 10 079 09 08 07 06 05 04

iii

To the Teacher iv

Reproducible Student Pages■ Hands-On Activities

MiniLAB: Try at Home Determining Weights in Newtons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3MiniLAB: Observing Mechanical Advantage–Pulleys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Lab: Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Lab: Use the Internet Methods of Travel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Laboratory Activity 1: Speed of Falling Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Laboratory Activity 2: Newton’s First Law of Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Foldables: Reading and Study Skills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

■ Meeting Individual NeedsExtension and Intervention

Directed Reading for Content Mastery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Directed Reading for Content Mastery in Spanish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Enrichment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Note-taking Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

■ AssessmentChapter Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Chapter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

■ Transparency ActivitiesSection Focus Transparency Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Teaching Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Assessment Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Teacher Support and PlanningContent Outline for Teaching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T2Spanish Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T5Teacher Guide and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T9

Table of Contents

Additional Assessment Resources available with Glencoe Science:

• ExamView® Pro Testmaker• Assessment Transparencies• Performance Assessment in the Science Classroom• Standardized Test Practice Booklet• MindJogger Videoquizzes• Vocabulary PuzzleMaker at msscience.com• Interactive Chalkboard• The Glencoe Science Web site at: msscience.com• An interactive version of this textbook along with assessment resources are available

online at: mhln.com

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This chapter-based booklet contains all of the resource materials to help you teachthis chapter more effectively. Within you will find:

Reproducible pages for ■ Student Assessment■ Hands-on Activities■ Meeting Individual Needs (Extension and Intervention)■ Transparency Activities

A teacher support and planning section including ■ Content Outline of the chapter■ Spanish Resources■ Answers and teacher notes for the worksheets

Hands-On ActivitiesMiniLAB and Lab Worksheets: Each of these worksheets is an expanded version of each laband MiniLAB found in the Student Edition. The materials lists, procedures, and questionsare repeated so that students do not need their texts open during the lab. Write-on rules areincluded for any questions. Tables/charts/graphs are often included for students to recordtheir observations. Additional lab preparation information is provided in the Teacher Guideand Answers section.

Laboratory Activities: These activities do not require elaborate supplies or extensive pre-labpreparations. These student-oriented labs are designed to explore science through a stimu-lating yet simple and relaxed approach to each topic. Helpful comments, suggestions, andanswers to all questions are provided in the Teacher Guide and Answers section.

Foldables: At the beginning of each chapter there is a Foldables: Reading & Study Skillsactivity written by renowned educator, Dinah Zike, that provides students with a tool thatthey can make themselves to organize some of the information in the chapter. Students maymake an organizational study fold, a cause and effect study fold, or a compare and contraststudy fold, to name a few. The accompanying Foldables worksheet found in this resourcebooklet provides an additional resource to help students demonstrate their grasp of theconcepts. The worksheet may contain titles, subtitles, text, or graphics students need tocomplete the study fold.

Meeting Individual Needs (Extension and Intervention)Directed Reading for Content Mastery: These worksheets are designed to provide studentswith learning difficulties with an aid to learning and understanding the vocabulary andmajor concepts of each chapter. The Content Mastery worksheets contain a variety of formatsto engage students as they master the basics of the chapter. Answers are provided in theTeacher Guide and Answers section.

To the Teacher

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Directed Reading for Content Mastery (in Spanish): A Spanish version of the DirectedReading for Content Mastery is provided for those Spanish-speaking students who are learning English.

Reinforcement: These worksheets provide an additional resource for reviewing the con-cepts of the chapter. There is one worksheet for each section, or lesson, of the chapter.The Reinforcement worksheets are designed to focus primarily on science content and lesson vocabulary, although knowledge of the section vocabulary supports understanding ofthe content. The worksheets are designed for the full range of students; however, they willbe more challenging for your lower-ability students. Answers are provided in the TeacherGuide and Answers section.

Enrichment: These worksheets are directed toward above-average students and allow themto explore further the information and concepts introduced in the section. A variety offormats are used for these worksheets: readings to analyze; problems to solve; diagrams to examine and analyze; or a simple activity or lab which students can complete in the classroom or at home. Answers are provided in the Teacher Guide and Answers section.

Note-taking Worksheet: The Note-taking Worksheet mirrors the content contained in theteacher version—Content Outline for Teaching. They can be used to allow students to takenotes during class, as an additional review of the material in the chapter, or as study notesfor students who have been absent.

AssessmentChapter Review: These worksheets prepare students for the chapter test. TheChapter Review worksheets cover all major vocabulary, concepts, and objectives

of the chapter. The first part is a vocabulary review and the second part is a concept review.Answers and objective correlations are provided in the Teacher Guide and Answers section.

Chapter Test: The Chapter Test requires students to use process skills and understand content.Although all questions involve memory to some degree, you will find that your students willneed to discover relationships among facts and concepts in some questions, and to use higherlevels of critical thinking to apply concepts in other questions. Each chapter test normallyconsists of four parts: Testing Concepts measures recall and recognition of vocabulary andfacts in the chapter; Understanding Concepts requires interpreting information and morecomprehension than recognition and recall—students will interpret basic information anddemonstrate their ability to determine relationships among facts, generalizations, definitions,and skills; Applying Concepts calls for the highest level of comprehension and inference;Writing Skills requires students to define or describe concepts in multiple sentence answers.Answers and objective correlations are provided in the Teacher Guide and Answers section.

Transparency ActivitiesSection Focus Transparencies: These transparencies are designed to generate interestand focus students’ attention on the topics presented in the sections and/or to assess

prior knowledge. There is a transparency for each section, or lesson, in the Student Edition.The reproducible student masters are located in the Transparency Activities section. Theteacher material, located in the Teacher Guide and Answers section, includes TransparencyTeaching Tips, a Content Background section, and Answers for each transparency.

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Teaching Transparencies: These transparencies relate to major concepts that will benefitfrom an extra visual learning aid. Most of these transparencies contain diagrams/photosfrom the Student Edition. There is one Teaching Transparency for each chapter. The TeachingTransparency Activity includes a black-and-white reproducible master of the transparencyaccompanied by a student worksheet that reviews the concept shown in the transparency.These masters are found in the Transparency Activities section. The teacher material includesTransparency Teaching Tips, a Reteaching Suggestion, Extensions, and Answers to StudentWorksheet. This teacher material is located in the Teacher Guide and Answers section.

Assessment Transparencies: An Assessment Transparency extends the chapter content andgives students the opportunity to practice interpreting and analyzing data presented incharts, graphs, and tables. Test-taking tips that help prepare students for success on stan-dardized tests and answers to questions on the transparencies are provided in the TeacherGuide and Answers section.

Teacher Support and PlanningContent Outline for Teaching: These pages provide a synopsis of the chapter by section,including suggested discussion questions. Also included are the terms that fill in the blanksin the students’ Note-taking Worksheets.

Spanish Resources: A Spanish version of the following chapter features are included in thissection: objectives, vocabulary words and definitions, a chapter purpose, the chapter Activi-ties, and content overviews for each section of the chapter.

Reproducible Student Pages■ Hands-On Activities

MiniLAB: Try at Home Determining Weights in Newtons . . . . . . . . . . 3MiniLAB: Observing Mechanical Advantage–Pulleys. . . . . . . . . . . . . . . 4Lab: Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Lab: Use the Internet Methods of Travel . . . . . . . . . . . . . . . . . . . . . . . . . 7Laboratory Activity 1: Speed of Falling Objects . . . . . . . . . . . . . . . . . . . 9Laboratory Activity 2: Newton’s First Law of Motion . . . . . . . . . . . . . 13Foldables: Reading and Study Skills . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

■ Meeting Individual NeedsExtension and Intervention

Directed Reading for Content Mastery . . . . . . . . . . . . . . . . . . . . . . . . 17Directed Reading for Content Mastery in Spanish . . . . . . . . . . . . . . . 21Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Enrichment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Note-taking Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

■ AssessmentChapter Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Chapter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

■ Transparency ActivitiesSection Focus Transparency Activities . . . . . . . . . . . . . . . . . . . . . . . . . 42Teaching Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Assessment Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Motion, Forces, and Simple Machines 1

ReproducibleStudent Pages

2 Motion, Forces, and Simple Machines

Hands-OnActivities

Hands-On Activities

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Determining Weights in Newtons

Analysis1. Subtract your weight from each of the combined weights to calculate the weight of each object

in pounds.

2. Multiply the weight of each object in pounds by 4.4 to calculate its weight in newtons.

3. Calculate your own weight in newtons.Ha

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Procedure1. Stand on a bathroom scale and measure your weight.

2. Hold a large book, stand on the scale, and measure the combined weight ofyou and the book. Record your data in the table below.

3. Repeat step 2 using a chair, heavy coat, and a fourth object of your choice.

Data and Observations

Pounds

My weight

My weightwith a chair

My weightwith a coat

My weightwith a book

Newtons

My weight with

a ____________


Name Date Class

Observing Mechanical Advantage—Pulleys

Procedure1. Tie a 3-m-long rope to the middle of a broomstick or dowel and hold this

stick horizontally. Another student should hold another stick horizontally.Wrap the rope around both sticks four times, leaving about 0.5 m betweenthe sticks.

2. A third student should pull on the rope while the other two students try tokeep the sticks from coming closer together.

3. Observe what happens. Repeat using only two wraps of the rope and thenusing eight wraps.

Hands-On Activities

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Analysis1. Describe what you observed. Could the students hold the sticks apart?

2. Compare and contrast the results with two, four, and eight turns of the rope around the sticks.

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Lab PreviewDirections: Answer these questions before you begin the Lab.

1. Should you conduct this lab on a flat surface or on a hill?

2. For how long should you record the distance traveled by the ball at 1-s intervals?

What happens when you roll a small ball down a ramp? It speeds up as ittravels down the ramp, and then it rolls across the floor and eventually itstops. You know that as the ball travels down the ramp, gravity is acting tomake it speed up. Think about the forces that are acting on the ball as it rollsacross the floor. Is there a net force acting on the ball? How would you describethe motion of the ball?

Real-World QuestionHow does a ball move when the forces acting onit are balanced and when they are unbalanced?

Materialssmall ball or marblestopwatchmeterstick or tape measuregraph paper

Goals■ Demonstrate the motion of a ball with

balanced and unbalanced forces acting on it.■ Graph the position versus time for the

motion of the ball.

Safety Precautions

Procedure1. Place the ball on the floor or a smooth, flat

surface.

2. Roll the ball across the floor by giving it agentle push.

3. Record Data As the ball is rolling and nolonger being pushed, have one student keeptrack of the time and have other studentsrecord the distance at 1-s intervals for atleast 5 s to 10 s.

4. Record anything else that you observedabout how the ball moved.

5. Calculate from your data the distance theball has traveled at each second.

6. Make a graph of the distance the balltravels versus time. Plot the distancetraveled on the vertical y-axis and the timeon the horizontal x-axis.

7. Choose three one-second time intervals.Calculate the speed of the ball in each ofthose time intervals.

Motion

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Conclude and Apply1. Describe how the speed of the ball changes as it rolls along the floor.

2. Describe the forces acting on the ball before you pushed it and it was at rest. Infer whether theforces acting on the ball were balanced or unbalanced.

3. Describe the forces acting on the ball as it rolled across the floor. Infer whether the forcesacting on the ball were balanced or unbalanced.

Hands-On Activities

Communicating Your Data

Compare your graphs and results with those of other students in your class.

(continued)

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Name Date Class

How long does it take you to get to the other side of town? How long does ittake to get to the other side of the country? If you were planning a roadtrip from New York City to Los Angeles, how long would it take? Howwould your trip change if you flew instead? When you plan a trip or vaca-tion, it is useful to first estimate your travel time. Travel time depends onthe vehicle you use, how fast you travel, the route you take, and even theterrain. For example, driving over rugged mountains can take longer thandriving over flat farmland. With this information, you can plan your tripso you arrive at your final destination on time. Form a hypothesis aboutwhat is the fastest form of travel.

Real-World QuestionWhat’s the fastest way to travel between twospecific locations?

Goals■ Research travel times.■ Compare travel times for different methods

of travel.■ Evaluate the fastest way to travel between

two locations.■ Design a table to display your findings and

communicate them to other students.

Data SourceSCIENCEOnline Go to the Glencoe ScienceWeb site at msscience.com for more informa-tion on travel times, methods of travel, dis-tances between locations, and data from otherstudents.

Make a Plan1. Choose a starting point and a final

destination.2. Identify the routes commonly used

between these two locations.3. Determine the common forms of travel

between these two locations.4. Research how to estimate travel time.

What factors can make your trip take moreor less time?

Follow Your Plan1. Make sure your teacher approves your plan

before you start.2. Calculate the travel time and distance

between your two locations for differentmethods of travel.

3. Record your data on a separate sheet ofpaper.

Use the Internet

Methods of Travel

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Analyze Your Data1. Analyze the data recorded to determine the fastest method of travel. Was it better to drive or

fly? Did you investigate another method of travel?


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2. Calculate the average speed of the methods of travel you investigated. Which method had thefastest speed? Which method had the slowest?

3. Organize Data Use a computer (home, library, or computer lab) to create a chart that com-pares the travel times, average speeds, and distances for different methods of travel. Use yourchart to determine the fastest method of travel. What factors add to travel time?

Conclude and Apply1. Compare your findings to those of your classmates and data posted on the Glencoe Science

Web site. What is the greatest distance investigated? The shortest?

2. Draw Conclusions What factors can affect travel time for the different methods? How wouldyour travel time be different if you didn’t have a direct flight?

3. Infer how the average speed of an airplane flight would change if you included your trips toand from the airport and waiting time in your total travel time.

Hands-On Activities

(continued)

Communicating Your Data

Find this lab using the link below. Post your data in the table provided. Combine your datawith those of other students and make a class travel booklet that estimates travel times forvarious locations around the world.

msscience.com

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Speed of Falling Objects

Galileo attempted to prove that objects of different mass will reach the ground at the same timewhen dropped from the same height. But this was difficult, since the objects fell so quickly hecouldn’t tell whether or not they actually hit the ground together. Galileo thought that if he couldslow down the objects, he would be able to make more accurate observations.

StrategyYou will show the speeds of falling objects of

different mass.You will compare the speeds of falling objects

of different mass.

Materials masking tape 15 cm × 150 cm gutter*15 cm × 150 cm board with sideschair2 marbles (each of different mass)index card*Alternate Materials

Procedure1. Place a strip of masking tape straight

across each end of the gutter (one neareach end of the board). See Figure 1.

2. Rest one end of the gutter on top of theback of the chair. (The top of the guttershould be at shoulder height or higher.)See Figure 1.

3. Place both marbles on one edge of the tape atthe top of the gutter. This is the starting line.

4. Have your partner position himself or her-self near the tape at the bottom. This is thefinish line.

5. Hold an index card in front of the marbles.Raise it to release both marbles at the same time.

6. Have your partner watch to see the orderin which the marbles cross the finish line.

7. Record the results by putting a checkmarkin the appropriate column in Table 1 in theData and Observations section.

8. Repeat the experiment two more timeswith the marbles positioned as in step 3.

9. Exchange the position of the marbles at the starting line and run the experimentthree more times (six times in all). Recordyour results.

10. Repeat the experiment placing the gutterat a different angle to the floor. Recordyour results in Table 2.

Figure 1

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Laboratory Activity 1 (continued)

Name Date Class


Table 1

Table 2

Questions and Conclusions1. How do the speeds of the rolling marbles compare?

2. Was there any difference in speed after you exchanged positions of the marbles?

Hands-On Activities

Trial

1

2

3

4

5

6

Large marble went faster Small marble went faster Both went at same speed

Slope _________________________

Trial

1

2

3

4

5

6

Large marble went faster Small marble went faster Both went at same speed

Slope _________________________

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Name Date Class

3. Why might it be important to change the position of the marbles for one half of the trials?

4. Compare and contrast your results with the ramp at different angles.

5. What can you conclude about the speed of falling objects of different mass?

6. Compare and contrast the motion of marbles rolling down the ramp with the motion ofmarbles that are dropped.

Strategy Check

Can you show the speeds of falling objects of different mass?

Can you compare the speeds of falling objects of different mass?

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Newton’s First Law of Motion

One of Isaac Newton’s laws of motion states that all bodies at rest tend to remain at rest unlessa force acts on them. However, once a body is set in motion by an outside force, the body movesin a straight line until another force causes it to change speed or direction. The force that changesthe motion of the body may be air pressure, friction, or another body.

StrategyYou will measure the amount of force needed to set a body in motion.You will deduce the relationship between the force needed to start a body in motion and the mass

of the body.

Materials balancebricksspring scale

Procedure1. Determine the mass of one brick. Record it

in Table 1.2. Attach the brick to the spring scale. Pull

the brick slowly across the floor.3. Record the force needed to start the brick

in motion. Record the force needed to keepthe brick in motion.

4. Determine the mass of the second brick.Add that to the mass of the first brick andrecord it in Table 1.

5. Repeat steps 2 and 3 with the second brickon top of the first brick.

6. Determine the mass of the third brick. Addthat to the mass of the other bricks andrecord it in Table 1.

7. Repeat steps 2 and 3 with the third brickon top of the other two bricks.

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Table 1

Number of bricks Mass (kg)Start Keep in motion

Force (N)

1

2

3


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Questions and Conclusions1. What is the outside force that starts the brick(s) in motion?

2. Compare the force needed to start the brick(s) in motion and the force needed to keep thebrick(s) in motion.

3. Compare the force required to keep the brick(s) in motion to the mass of the brick(s).

4. State the relationship between the force needed to start a body in motion and the body’s mass.

5. What force resists the motion of the bricks in all cases?

6. Explain in terms of Newton’s law of motion what happens to a passenger who is standing inthe aisle of a bus when the bus stops suddenly. Use diagrams to help explain your answer.

Hands-On Activities

Strategy Check

Can you measure the amount of force needed to set a body in motion?

Can you state the relationship between the force needed to start a body in motion and the mass of the body?

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Directions: Use this page to label your Foldable at the beginning of the chapter.

KnowWantLearned

Name Date Class

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MeetingIndividual Needs

Meeting Individual Needs

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Directions: Use the formula v = d/t to answer the following question.

1. Julio rides his bike 12 km in 1.5 h. Determine the average speed at which Julio rode.

Directions: The figure below illustrates Newton’s third law of motion. Use it to answer the questions below.

2. Draw arrows on the figure above to show the direction in which the oars mustmove to send the boat forward.

3. Do the arrows you drew in the figure represent an action force or a reaction force?

Directions: Answer the following question about weight.

4. If your weight is 490 N and you stand on a box that exerts a normal force of440 N, what will happen?

Directions: Answer the following question on the lines provided.

5. A third-class lever has a mechanical advantage of less than one. Why are third-class levers used if this is the case?

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Content Mastery

OverviewMotion, Forces, and Simple Machines

Name Date Class


Section 1 ■ MotionSection 2 ■ Newton’s Laws

of MotionDirections: Study the following diagram. Then answer questions 1 and 2 on the lines provided.

1. What distance will John travel if he goes from A to B to C to D and back again to A?

2. If John covers the distance in two minutes, what is his average speed in metersper minute?

Directions: Write speed or acceleration to indicate what each unit below measures.

3. m/s

4. km/h

5. m/s/s

Directions: Fill in the blanks in the chart below.

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C D

AB 120 m

90 m

50 m

70 m

First law

Second law

Third law

Newton’s Laws of Motion

An object at rest will remain at rest or an object moving straight at constant

speed will continue this motion until a 6. ____________________ acts on it.

An object that has a force acting on it will 7. ___________________ in the

direction of the force.

Forces always occur in equal but 8. ___________________ pairs.

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Directions: Use the clues below to complete the puzzle.

Across

2. A machine that uses only one movement

4. The force you apply when using a machine

5. Probably the first simple machine

Down

1. Work = force × _______

3. Inclined _______; ramp

Directions: Place a check mark (✓) next to each statement that is true. If the statement is false, rewrite thestatement to make it true.

1. In order for you to do work, you only need to apply force to an object.

2. A simple machine is one that always gives a mechanical advantage of 2.

3. Force can be expressed in units called newtons.

4. An inclined plane allows you to lift a heavy load by using greater force

over less distance.M

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Content Mastery

Section 3 ■ Work and Simple Machines

Name Date Class


Key Terms Motion, Forces, and Simple Machines

Directions: Use the following terms to complete the sentences below.

joules output force force lever

motion friction average speed net force

acceleration velocity

1. A push or a pull is a(n) ______________________________.

2. Newton’s laws explain ______________________________.

3. ______________________________ equals change in speed divided by time.

4. ______________________________ changes when speed changes, direction of

motion changes, or both factors change.

5. Work, like energy, is measured in ______________________________.

6. Mechanical advantage equals ______________________________ divided by

effort force.

7. ______________________________ equals total distance traveled divided by

travel time.

8. ______________________________ is a force that resists motion between two

surfaces that are in contact.

9. Probably the first simple machine invented by prehistoric humans was

the ______________________________.

10. The combination of all forces acting on an object is

the ______________________________.

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Movimiento, fuerzas y máquinas simples 21

Instrucciones : Usa la fórmula v = d/t para contestar la siguiente pregunta.

1. Julio anda en bicicleta 12 km en 1.5 h. Determina la rapidez promedio de Julio enesta travesía.

Instrucciones: La figura ilustra la tercera ley del movimiento de Newton. Úsala para contestar las preguntas.

2. Dibuja flechas en la figura que muestren la dirección en que deben moverse losremos para que el bote avance.

3. ¿Representan una fuerza de acción o una fuerza de reacción las flechas que dibujaste?

Instrucciones: Contesta estas preguntas sobre el peso.

4. Si pesas 490N y estás parado sobre una caja que ejerce una fuerza normal de440N, ¿qué sucederá?

Instrucciones: Contesta esta pregunta.

5. Una palanca de tercera clase tiene una ventaja mecánica de menos de uno. Si esasí, ¿por qué usamos palancas de tercera clase?

Lectura dirigida para

Dominio del contenidio

SinopsisMovimiento, fuerzas y máquinas simples

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Nombre Fecha Clase

22 Movimiento, fuerzas y máquinas simples

Sección 1 ■ El movimientoSección 2 ■ Las leyes del

movimiento de NewtonInstrucciones : Estudia el diagrama. Contesta luego las preguntas 1 y 2 en los espacios dados.

1. ¿Qué distancia viajará John si va de A a B a C a D y de regreso a A?

2. Si John cubre esa distancia en dos minutos, ¿cuál es su velocidad promedio enmetros por minuto?

Instrucciones: Escribe velocidad o aceleración para indicar lo que mide cada unidad.

3. m/s

4. km/h

5. m/s/s

Instrucciones: Llena los espacios en blanco de la tabla.

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AB 120 m

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Primera ley

Segunda ley

Tercera ley

Leyes del movimiento de Newton

Un cuerpo en reposo permanecerá en reposo y un cuerpo que se mueve en línea recta a velocidad constante continuará este movimiento hasta que un(a) 6. ____________________ actúe sobre él.

Un objeto que experimenta una fuerza actuando sobre él se7. ___________________ en la dirección de la fuerza.

Las fuerzas siempre ocurren en pares iguales pero 8. ___________________.

Satisface las necesidades individuales

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Instrucciones : Usa las claves para completar el crucigrama.

Horizontales

2. _______ inclinado; rampa

3. Máquina que usa un solo movimiento

4. La fuerza que aplicas cuando usas una máquina

Verticales

1. Trabajo = fuerza × _______

2. Probablemente la primera máquina simple

Instrucciones: Marca con una X la afirmación verdadera. Si la afirmación es falsa, vuelve a escribir la afir-mación en forma correcta en las líneas dadas.

1. Para realizar trabajo, sólo necesitas aplicarle una fuerza a un cuerpo.

2. Una máquina simple es aquella que siempre da una ventaja mecánica de dos.

3. La fuerza puede expresarse en unidades llamadas newtons.

4. Un plano inclinado permite levantar objetos pesados usando más fuerzaen una distancia más corta.



Sección 3 ■ Trabajo y máquinas simples

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Nombre Fecha Clase

24 Movimiento, fuerzas y máquinas simples

Términos clavesMovimiento, fuerzas ymáquinas simples

Instrucciones: Usa estos términos para completar las siguientes oraciones.

julios fuerza de salida fuerza palanca

movimiento fricción velocidad promedio fuerza neta

aceleración velocidad

1. Un empujón o un jalón es un(a) ______________________________.

2. Las leyes de Newton explican ______________________________.

3. El(La) ______________________________ es igual al cambio en velocidad

dividido por el tiempo.

4. El(La) ______________________________ cambia cuando cambia la veloci-

dad, cuando cambia la dirección del movimiento, o cuando ambos(as) cambian.

5. Al igual que la energía, el trabajo se mide en

______________________________.

6. La ventaja mecánica es igual a ______________________________ dividida

por la fuerza de esfuerzo.

7. El(La) ______________________________ es igual a la distancia total reco-

rrida dividida por el tiempo de viaje.

8. El(La) ______________________________ es la fuerza que resiste el

movimiento entre dos superficies en contacto.

9. Es posible que la primera máquina simple que inventaron los humanos pre-

históricos haya sido el(la) ______________________________.

10. La combinación de todas las fuerzas que actúan sobre un cuerpo es el(la)

_____________________________.

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Directions: Identify what each of the following formulas is used to find.1. (change in speed)/time

2. acceleration × time

3. (total distance traveled)/time

4. 1/2 (acceleration)(time)2

Directions: The graph shows the various speeds at which a worm travels over a 10-minute interval. Use thegraph to answer the questions that follow.

5. What is the greatest speed the worm reaches?

6. What is the worm’s acceleration during the first 2 minutes?

7. How fast is the worm traveling as it goes from A to B?

8. How far does the worm travel from A to B?

9. What is the worm’s acceleration from A to B?

10. How does the worm’s motion change from B to C?

11. What is the worm’s acceleration during the last 2 minutes?

12. How would you describe the worm’s motion during the last 2 minutes?

13. How far does the worm travel during the last 2 minutes?

Motion

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Directions: A yo-yo with a mass 0.25 kg is suspended from a hook on a ceiling. Use the diagram at the bottomof the page to answer the questions.1. Identify which of Newton’s laws explains what happens in each of the following steps.

2. What is the net force acting on the yo-yo in step b?

3. In step e, what force causes the yo-yo to slow down and stop?

4. If a net force of 0.2 N is applied in step c, use the space below to calculate how fast the yo-yoaccelerates.

5. If the same net force is applied to a yo-yo with a mass of 0.5 kg, how will the rate of accelerationbe affected? Why?

6. If the hook exerts a force of 0.001N on the ceiling, how much forcedoes the ceiling exert on the hook?

Reinforcement22


a. Earth pulls the yo-yo downwardand the yo-yo pulls Earth upward.

b. The yo-yo doesn’t move.

d. The yo-yo keeps swingingback and forth.

e. The yo-yo slows downand eventually stops.

f. The yo-yo pulls on the hook andthe hook pulls on the yo-yo.

c. Someone pushes on the yo-yo inthe direction shown by the arrow,and the yo-yo moves.

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Directions: Describe what is happening in each situation as work or no work.

Work and Simple Machines

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1. ____________________ 2. ____________________ 3. ____________________

Directions: Name two situations in which no work is done to an object.

4.

5.

Directions: Answer the following questions on the lines provided.

6. What two things must occur for effort to count as work?

7. How is work measured?

8. What is mechanical advantage?

9. How do the three classes of levers differ?

10. How does a pulley make work easier if it doesn’t multiply force?


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The Art of Motion

Think back to the last time you read a comic book or saw a cartoon in the newspaper. Chancesare that somewhere in that comic strip, the cartoonist showed a character in motion. Do youremember how it was done? Perhaps the cartoonist inserted horizontal lines to show motion.Maybe the cartoonist altered the actual shape of an object. List three techniques for showingmotion in cartoons.

1.

2.

3.

Directions: Using simple figures, motion lines, or other techniques, draw three cartoon panels of two automobiles on a highway. One is moving at a constant speed and one is accelerating.

4. What formulas did your cartoon illustrate?

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The Physics of Hitting a Baseball

1. Which of Newton’s laws causes the bat to move back from the point of impact?

2. How do Newton’s other laws apply to this situation?

3. How might studying physics help people improve performance in other sports?

What does Newton have to do with hittinga powerful homerun or line drive? Accordingto Alan Nathan, a physicist from the Univer-sity of Illinois, understanding the laws ofphysics can help batters improve their skill.Some people believe that physical strength canhelp send a ball sailing over the fence. Othersbelieve that hitting the ball with the “sweetspot” of the bat, the place where batters feelalmost no vibration after a hit, is the best wayto score a home run. The laws of physics,however, prove both theories to be false.

When ball meets bat, the impact from thebat reverses the direction of the ball. Nathanrecommends imagining the ball as a spring andthe force between the bat and ball compressingand then expanding, sending the ball flying.However, the impact is extremely brief—lessthan one-thousandth of a second. In that time,some energy is lost to friction.

A Bigger BatIn addition, because of the law of action-

reaction, the ball exerts an opposite force onthe bat, causing the bat to move backward andtaking energy away from the spring motion of the ball. Because of this fact, Nathan rec-ommends using a heavier bat in order to offset the backward movement after impact.

Furthermore, the impact causes some energyto travel as vibrations along the wood or alu-minum. Interestingly, the “sweet spot” thatmany batters prefer because it causes the leastamount of vibration is not the ideal spot touse for hitting the ball.

Finding the “Best Spot”To find the best spot for hitting a baseball,

Nathan used a computer to perform calcula-tions—formulas used to analyze the vibrationof airplane wings or bridges. The ideal spot hewas searching for would have to account notonly for vibrations, however, but also for thecircular motion of the bat as it strikes. Thatmotion increases the speed of the ball. Theresults of his calculations are that with a 34-inch bat, the best point of impact is about sixinches from the tip. With the help of anotherresearcher, Nathan was able to test his resultsand found them to be accurate. Incidentally,physical strength cannot help at this point inthe activity. All that matters, according to thelaws of physics, is the moment and point ofimpact. Nathan states that “if the batter couldlet go of the bat just prior to hitting the ball,there would be no noticeable effect. The ballwould respond in exactly the same way.” Giventhese findings, perhaps spring training will oneday include some work in the physics lab.

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Bicycle Improvements

The first bicycles did not have multiplegears for ease of riding. Cyclists worked hardto cover ground. They sat over the front wheel because the pedals were attacheddirectly to the wheel’s axle. Rotating the pedalsonce around moved the front wheel only onecomplete revolution. The invention of thechain drive allowed the rider to sit in a safer,more balanced position between the front andback wheels.

Chain DrivesChain drives transfer the power from the

rider’s legs, which push down on the pedalsattached to levers (the cranks), which turn the axle of the toothed wheel (front sprocket,or chain ring). The chain is a continuous loop attached to the chain ring and a rearsprocket. As the chain ring rotates, it movesthe chain, which moves the rear sprocket,which turns the rear wheel’s axle. Thus, theinvention of the chain drive meant that a rider propelled the bike forward by movingthe rear wheel, not the front one. If you think chain drives resemble pulley systems,you’re right!

GearsLater, the addition of gears with varying

ratios made it easier to ride up steep inclinesand pedal more efficiently. Gear ratios are fig-ured by dividing the number of teeth in thefront sprocket by the number of teeth in therear sprocket. If there are 54 teeth in front and27 in back, the ratio is 2 to 1 because 54 ÷ 27= 2. This means that the rear sprocket goesaround twice each time the rider moves thechain ring one complete revolution. If the rearsprocket has 13 teeth, the ratio is about 4 to 1.One turn of the pedals will rotate the backsprocket four times. On downhills or levelground, a rider doesn’t have to work as hardto move the bicycle in the “fourth” gear as inthe “second.”

On the other hand, the steeper the incline,the more difficult it is to ride a bike in a highgear (think of lifting a heavy object straight upinstead of pushing it along a ramp). In thiscase the rider’s goal is to easily turn the pedalsseveral times before the rear sprocket com-pletes a revolution. The rider needs to shiftinto a lower gear.

Directions: Complete the table below by computing the gear ratios (round to the nearest whole number).

Table 1

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a

b

c

d

11 60

22 54

41 84

60 54

Number of teethin rear sprocket

Gear Gear ratioNumber of teethin front sprocket

1.

2.

3.

4.

5. Which gear would be best for riding up a steep hill? Explain.

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Section 1 MotionA. ______________ involves distance and time.

1. ________________ speed—calculated as total distance traveled divided by travel time

2. ______________________ speed—an object’s speed at a particular moment

3. When instantaneous speed does not change, an object is moving at _________________

speed; average speed and instantaneous speed are the _____________ in this situation.

4. Distance can be calculated if an object is moving at constant speed over a particular time

period; total distance traveled equals ______________________ times time.

B. Speed and direction of motion is _________________.

C. _____________________ is the change in velocity divided by the time needed for the change

to occur.

1. Acceleration can be calculated using a formula: acceleration equals change in

______________ divided by time.

2. Acceleration can be shown on a speed-time graph.

Section 2 Newton’s Laws of MotionA. ______________—a push or a pull

1. When a force acts on an object, it ________________ the object’s acceleration.

2. Two or more forces that cancel each other out are _________________ forces.

3. Two or more forces that do not cancel each other out are ___________________ forces.

4. The combination of all forces acting on an object is the ____________ force.

B. Newton’s _______________________—explain how forces cause motion

1. Newton’s first law—a moving object moves in a straight line with _________________

speed unless a force acts on it.

a. _________________—a force that resists movement between two surfaces in contact

b. An object’s tendency to resist a change in motion is ________________; the more mass

an object has, the greater its inertia.

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2. Newton’s second law—if an object is acted upon by a ____________ force, the change in

velocity will be in the direction of the ____________ force; acceleration can be calculated as

acceleration equals net force divided by mass.

3. Newton’s third law—forces always occur in equal but _________________ pairs; the equal

and opposite forces act on different objects, so they are not balanced forces.

Section 3 Work and Simple MachinesA. _____________

1. Occurs when a force causes an object to move in the same direction that the force is applied

2. Calculated as work equals ______________ times distance

B. A _______________ machine uses only one movement; a _________________ machine is a

combination of simple machines.

1. Mechanical __________________ is the number of times force is multiplied; calculated as

mechanical advantage equals output force divided by input force.

2. An ______________ machine would experience no friction, so work in would equal work out.

3. _____________ machines do experience friction, so work out is always less than work in.

C. ________________—an object with a groove, like a wheel, with a rope or chain running

through the groove; changes the direction of the input force

D. A lever is a rod or plank that pivots about a fixed point called the ________________.

1. The fulcrum is between the input force and the output force in a

____________________ lever.

2. In a _____________________ lever, the output force is between the input force and the

fulcrum.

3. The input force is between the output force and the fulcrum in a

____________________ lever

4. The ______________ and _____________ provide a mechanical advantage greater than one.

E. An _______________________ or ramp allows an object to be lifted over a greater distance

using less force.

1. A ______________ is a moving inclined plane with one or two sloping surfaces.

2. ______________—inclined plane wrapped around a post


Note-taking Worksheet (continued)


Assessment

Assessment

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Chapter Review


Part A. Vocabulary Review

Asse

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Directions: Write the term that matches each description below on the spaces provided. The heavily-boxed letters will spell something for which Isaac Newton is famous.

1. rate at which speed or direction changes2. measures the quantity of matter3. ______ = force × distance4. total distance divided by time5. speed of an object and its direction

of motion6. a push or pull7. an inclined plane8. force that resists motion between objects

in contact

9. speed of an object at any instant in time10. the number of times your force is

multiplied11. force that produces an acceleration12. tendency to resist a change in motion13. the boxed letters spell:

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Chapter Review (continued)


Part B. Concept ReviewDirections: Fill in the blanks with the correct terms.

1. A machine that uses only one movement is a(n) ______________________________.

2. An object is accelerating if its ______________________________ or

______________________________ changes.

3. In a machine, the effort force you apply is used to overcome a

______________________________ force.

4. The speed of an object and its direction of motion are its

______________________________.

5. The speed of an object at any instant in time is its ______________________________ speed.

6. The less mass a moving object has, the _____________________________ it is to stop it.

7. Force pairs act on ______________________________ object(s).

8. A spring scale is used to measure ______________________________.

9. Machines can change the size of the force you apply, and/or change the

______________________________ of the force.

10. Friction always ______________________________ an object.

11. The smoother a surface is, the ______________________________ the force of friction.

12. According to Newton’s second law, an object acted on by a net force will accelerate in the

direction of ______________________________.

13. If a person pushes on a wall with a force of 35 N, the force acting on the person

is ______________________________.

14. To do work, a(n) ______________________________ must be applied and the object mustmove.

15. A ball dropped from a height of 125 m takes 5 s to hit the ground and is traveling at the rateof 50 m/s when it hits.

a. The average speed of the ball in meters per second is ______________________________.

b. The ball’s acceleration is ______________________________.

c. After 3 seconds, the ball travels at a rate of ______________________________.

d. After 4 seconds, the ball has traveled a distance of ______________________________.

Assessment

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Chapter Test

Motion, Forces,and Simple Machines

I. Testing ConceptsDirections: In the blank at the left, write the letter of the term that best completes each statement.

1. It would probably be easiest to ride a bicycle across ______.a. a sidewalk b. the grass c. sand d. gravel

2. The force that always acts opposite to the direction of the motion of an object iscalled ______.a. gravity b. inertia c. friction d. none of these

3. According to Newton’s third law, forces always occur in ______ pairs.a. equal but opposite c. unequal but complementaryb. unequal but opposite d. equal but complementary

4. Newton first described gravity while watching ______.a. smoke rise b. a car accelerate c. someone walking d. an apple falling

5. You would NOT use ______ to find the acceleration of an object.a. time b. initial speed c. final speed d. weight

6. Newton’s ______ law of motion explains why you may lean sideways in a car if thedriver turns a corner too quickly.a. primary b. first c. second d. third

7. ______ is the speed of an object and its direction of motion.a. Friction b. Mass c. Gravity d. Velocity

8. To calculate an average speed, you would use ______.a. weight and time c. accelerationb. weight and distance d. distance and time

9. ______ is used to describe an object slowing down because of decreasing speed.a. Acceleration c. Negative accelerationb. Average speed d. Inertia

10. A bottle opener is a(n) ______.a. first-class lever b. second-class lever c. third-class lever d. inclined plane

11. An object that has a ______ will accelerate in the direction of the force.a. normal force b. net force c. frictional force d. speed

12. ______ is the rate at which an object covers a given distance.a. Acceleration b. Speed c. Force d. Motion

13. ______ is NOT a force.a. Gravity b. Mass c. Friction d. all of these

14. A 1-cm screw with a 4-cm thread would have a mechanical advantage of ______.a. one b. two c. three d. four

15. Stepping from a wagon and watching the wagon move away from you is an exampleof Newton’s ______ law.a. first b. second c. third d. gravitational

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Chapter Test (continued)


Directions: Identify each statement as true or false. Rewrite false statements to make them correct.

16. Acceleration is a rate that can describe how speed or direction is changing.

17. A compound machine is a combination of simple machines.

18. A combination of pulleys increases the effort force, so the mechanical advantage isgreater than one.

19. Average speed does not include the time a car sits at red lights on the way home.

20. There is usually more friction on a smoother surface.

Directions: If the statement or term identifies a force, list its number under Force. If it does not identify a force,list its number under Not a force.

Assessment

Force Not a force

21. the time it takes to make a trip

22. the mass of a person on a scale

23. the acceleration of a car turning a corner

24. friction

25. speed

26. color

27. taste

28. the weight of a person standing still

29. gravity

30. pushing your friend toward the door

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II. Understanding Concepts

Skill: Making and Using TablesDirections: Complete the table below by calculating the missing values.

4. Use the information in the table above to answer the following questions.a. Which object has the greatest acceleration?

b. Which object has negative acceleration?

Skill: Concept Mapping

Directions: Complete the following concept map that describes what happens when a cue ball is struck by thecue and then collides with the 8-ball.

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Object Initial speed Final speed Time Acceleration

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0 m/s

0 m/s

1.

0 m/s

10 m/s

4 s

2 s

2 m/s 2

-4 m/s 2

2.

2 s 3.

cue strikes cue ball

cue ball rebounds 8-ball moves

cue ball strikes 8-ball

7. ____________in same direction

opposite

6. ____________

cue ball

5. ____________

cue ballaccelerates

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Skill: Designing an Experiment8. How could you use a board and different materials found in the classroom to show the effect of

friction on a rolling marble?

III. Applying ConceptsDirections: Do the following calculations. Show your work on the lines provided.

1. What is the average speed of a car traveling 210 km in 3 h?

2. Calculate the distance an object travels if its speed is 60km/h and it travels for 6 h.

3. Calculate the mass of an object with a force of 20 N and an acceleration of 2 m/s2.

4. Calculate the acceleration of an object that starts at rest and accelerates smoothly to 20 m/s in 5 s.

5. Calculate the work of a weight lifter lifting a 400-N weight a distance of 2 m.

IV. Writing SkillsDirections: Answer the following questions using complete sentences.

1. According to Newton’s first law, if an arrow is shot in an open field, it should keep moving.Explain why the arrow eventually stops.

2. Explain what inertia means.

Assessment

Transparency Activities


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Section FocusTransparency Activity11


Calvin is right; calculating how fast you’re going is math. WhetherCalvin does it himself or a speedometer does it for him, a calculationhas to be made in order to find his speed.

It Must Be Math

1. What two ways does the cartoon mention for measuring speed?

2. Which method is best for measuring speed at a specific point onthe hill? Which method is best for comparing how quickly twodifferent sleds go down the hill?

3. Describe how the motion of the sled changes when it gets to thebottom of the hill.

CALVIN AND HOBBES © Watterson.Reprinted with permission of UNIVERSAL PRESS SYNDICATE. All rights reserved.

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Skydiving is a sport that many people enjoy. Experienced jumpersenjoy the feeling of free-fall before opening their parachutes. Work-ing together, a team of skydivers can link arms to make formationslike the one you see.

Bird’s Eye View

1. How will the skydivers’ motion change when their parachutesopen?

2. Does their motion continue to change after their parachutesopen? Explain.

3. Would a heavier person fall more quickly than a lighter person?Give a reason for your answer.

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Moving is pretty hard work, but there are things that can help makeit easier. As you look at this picture, try to imagine what it would belike if the man had only his bare hands to move the boxes.

Movin’ On

1. What do you see that helps the man move the boxes?

2. Where do you see wheels in this photograph?

3. If you had to load this truck with heavy boxes, what tools wouldyou want on hand?

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Teaching TransparencyActivity22 Newton’s Laws

of Motion


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Teaching Transparency Activity (continued)

1. If an object is accelerating, what can you infer about the forces acting on it?

2. What force set the ball in the top picture in motion? What force is slowing it down?

3. If the same force is applied to the refrigerator and the shopping cart, which will experiencegreater acceleration? Why?

4. Which law of motion do the action and reaction arrows illustrate?

5. When you walk, what is pushing against your foot?

6. In the photo of the swimmer, you can see the action and reaction arrows are the same size.Why don’t these forces cancel one another out?


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AssessmentTransparency Activity

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Directions: Carefully review the diagram and answer the following questions.

Motion, Forces, andSimple Machines

1. Newton’s third law says that forces act in opposing pairs. Accord-ing to this information, what is the direction of the force the railroad tracks exert on the train?A 1B 2C 3D 4

2. Which arrow indicates the force of friction?F 1G 2H 3J 4

3. If the forces indicated by arrows 2 and 4 are the same size, which ofthe following could describe the train’s motion?A Speeding up before reaching a hillB Slowing down as it approaches a downward slopeC Running along a straight track at a constant speedD Applying the brakes slightly

Motion, Forces, and Simple Machines T1

Teacher Support and PlanningContent Outline for Teaching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T2Spanish Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T5Teacher Guide and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T9

Teacher Supportand Planning

T2 Motion, Forces, and Simple Machines

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Motion, Forces, andSimple Machines

Section 1 Motion

A. Speed involves distance and time.

1. Average speed—calculated as total distance traveled divided by

travel time

2. Instantaneous speed—an object’s speed at a particular moment

3. When instantaneous speed does not change, an object is moving at constant speed; average

speed and instantaneous speed are the same in this situation.

4. Distance can be calculated if an object is moving at constant speed over a particular time

period; total distance traveled equals average speed times time.

B. Speed and direction of motion is velocity.

C. Acceleration is the change in velocity divided by the time needed for the change to occur.

1. Acceleration can be calculated using a formula: acceleration equals change in speed divided by time.

2. Acceleration can be shown on a speed-time graph.

DISCUSSION QUESTION:What two variables are involved in velocity? speed and direction of motion

Section 2 Newton’s Laws of Motion

A. Force—a push or a pull

1. When a force acts on an object, it changes the object’s acceleration.

2. Two or more forces that cancel each other out are balanced forces.

3. Two or more forces that do not cancel each other out are unbalanced forces.

4. The combination of all forces acting on an object is the net force.

B. Newton’s laws of motion—explain how forces cause motion

1. Newton’s first law—a moving object moves in a straight line with constant speed unless a

force acts on it.

a. Friction—a force that resists movement between two surfaces in contact

b. An object’s tendency to resist a change in motion is inertia; the more mass an object has,

the greater its inertia.

Underlined words andphrases are to be filled in by students on theNote-taking Worksheet.

Teacher Support & Planning

Content Outlinefor Teaching

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2. Newton’s second law—if an object is acted upon by a net force, the change in velocity will

be in the direction of the net force; acceleration can be calculated as acceleration equals net

force divided by mass.

3. Newton’s third law—forces always occur in equal but opposite pairs; the equal and opposite

forces act on different objects, so they are not balanced forces.

DISCUSSION QUESTION:How are mass and inertia related? The greater an object’s mass, the greater its inertia.

Section 3 Work and Simple Machines

A. Work

1. Occurs when a force causes an object to move in the same direction that the force is applied

2. Calculated as work equals force times distance

B. A simple machine uses only one movement; a compound machine is a combination of

simple machines.

1. Mechanical advantage is the number of times force is multiplied; calculated as mechanical

advantage equals output force divided by input force.

2. An ideal machine would experience no friction, so work in would equal work out.

3. Real machines experience friction, so work out is always less than work in.

C. Pulley—an object with a groove, like a wheel, with a rope or chain running through the

groove; changes the direction of the input force

D. A lever is a rod or plank that pivots about a fixed point called the fulcrum.

1. The fulcrum is between the input force and the output force in a first-class lever.

2. In a second-class lever, the output force is between the input force and the fulcrum.

3. The input force is between the output force and the fulcrum in a third-class lever

4. The wheel and axle provide a mechanical advantage greater than one.

E. An inclined plane or ramp allows an object to be lifted over a greater distance using less force.

1. A wedge is a moving inclined plane with one or two sloping surfaces.

2. Screw—inclined plane wrapped around a post

DISCUSSION QUESTION:What is mechanical advantage? the number of times force is multiplied by a machine

Content Outline for Teaching (continued)

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Movimiento, fuerzas y máquinas simples T5

SpanishResources

Movimiento, fuerzas y máquinas simples

El movimiento Lo que aprenderás■ A definir velocidad y aceleración.■ A relacionar la aceleración con el cambio de

velocidad.■ A calcular distancia, velocidad y aceleración.

Vocabularioaverage speed / velocidad media: tasa de

movimiento que se calcula dividiendo la dis-tancia recorrida por la cantidad de tiempo quese tarda en recorrer esa distancia.

velocity / velocidad: rapidez de un cuerpo y sudirección de movimiento; cambia cuandocambia la rapidez, cuando cambia la direccióndel movimiento o cuando las dos cambian.

instantaneous speed / velocidad instantánea:rapidez de un objeto en cualquier momentodado.

acceleration / aceleración: cambio en velocidaddividido por la cantidad de tiempo que senecesita para que ocurra el cambio; se pre-senta cuando un cuerpo acelera, decelera ocambia de dirección.

Por qué es importanteEl movimiento puede describirse usando la dis-tancia, el tiempo, la velocidad y la aceleración.

Las leyes del movimiento de Newton

Lo que aprenderás■ A describir la forma en que las fuerzas afectan

al movimiento.■ A calcular la aceleración usando la segunda

ley del movimiento de Newton.■ A explicar la tercera ley del movimiento de

Newton.

Vocabularioforce / fuerza: un empuje o un jalón; el newton

es la unidad SI.

Newton’s laws of motion / leyes delmovimiento de Newton: conjunto de princi-pios que explica el movimiento de los objetos.

friction / fricción: fuerza resistente al movi-miento entre dos superficies que se tocan yque siempre actúa opuesta a la dirección delmovimiento.

inertia / inercia: tendencia a resistir un cambioen movimiento.

Por qué es importanteLas leyes de Newton explican movimientos tansimples como caminar y tan complicados comoel lanzamiento de un cohete.

Trabajo y máquinas simplesLo que aprenderás■ A definir trabajo.■ A distinguir los diferentes tipos de máquinas

simples.■ A explicar cómo las máquinas facilitan el

trabajo.

Vocabulariowork / trabajo: se lleva a cabo cuando una

fuerza aplicada causa el movimiento de uncuerpo en la dirección de la fuerza.

simple machine / máquina simple:dispositivo que facilita el trabajo con unmovimiento solamente; puede cambiar eltamaño o la dirección de una fuerza; entreeste tipo de máquina se incluyen la cuña,el tornillo, la palanca, la rueda y eje, lapolea y el plano inclinado.

compound machine / máquina compuesta:combinación de dos o más máquinas simples.

mechanical advantage / ventaja mecánica:número de veces que una máquina multiplicala fuerza de esfuerzo que se le aplica.

pulley / polea: máquina simple compuesta deuna rueda acanalada con una cuerda, cadena ocable que corre a lo largo de una ranura; unapolea cambia la dirección de la fuerza deesfuerzo y puede ser fija o movible.

lever / palanca: máquina simple hecha de unabarra libre para girar sobre un punto fijo.

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Spanish Resources (continued)

inclined plane / plano inclinado: máquina simpleque consta de una superficie inclinada, comouna rampa, que reduce la cantidad de fuerzaque se necesita para levantar algo, al aumentarla distancia sobre la cual se aplica la fuerza.

Por qué es importanteLas máquinas facilitan el trabajo.

Movimiento¿Qué sucede cuando dejas rodar una pelotapequeña por una rampa? La pelota acelera albajar la rampa, luego rueda por el piso y final-mente se detiene. Sabes que a medida que bajapor la rampa, la gravedad actúa para acelerar lapelota. Piensa en las fuerzas que están actuandosobre la pelota al rodar sobre el piso. ¿Actúauna fuerza neta sobre la pelota? ¿De qué man-era describirías el movimiento de la pelota?

Preguntas del mundo real¿Cómo se mueve la pelota cuando las fuerzasque actúan sobre ella están equilibradas ycuando no están equilibradas?

Materialespelota pequeña o canicametro o cinta métricacronómetropapel para graficar

Metas■ Demostrar el movimiento de una pelota

sobre la que actúan fuerzas equilibradas ydesequilibradas.

■ Graficar la posición de la pelota con relaciónal tiempo.

Medidas de seguridad

Procedimiento1. Coloca la pelota sobre el piso o una superfi-

cie plana y lisa.2. Rueda la pelota por el piso empujándo la

suavemente.

3. Anota datos Cuando la pelota ya ruede solahaz que un alumno anote el tiempo y queotros anoten la distancia a intervalos de 1 sdurante 5 ó 10 s.

4. Escribe todo lo que observes sobre elmovimiento de la pelota.

5. Calcula la distancia que la pelota recorriócada segundo.

6. Has un gráfico de la distancia que la pelotaviajó versus el tiempo. Dibuja la distanciarecorrida en el eje de y vertical y el tiempoen el eje de � horizontal.

7. Escoge tres intervalos de un segundo.Calcula la velocidad de la pelota en cadauno de esos intervalos.

Concluye y aplica1. Describe cómo cambió la velocidad de la

pelota a medida que rodaba por el piso.2. Describe las fuerzas que actuaron sobre la

pelota antes de empujarla, cuando estaba enreposo. Infiere si las fuerzas que actuaronsobre ella eran equilibradas o desequilibradas.

3. Describe las fuerzas actuando sobre lapelota a medida que rodaba por el piso.Infiere si las fuerzas que actuaron sobre ellaeran equilibradas o desequilibradas.

Comunica tus datosCompara tus gráficos con los de otrosestudiantes de tu clase.

Usa Internet Métodos de viaje

Preguntas del mundo real¿Cuánto tiempo te toma llegar al otro lado de laciudad? ¿Cuánto tiempo toma llegar al otrolado del país? ¿Si estuvieras planeando un viajede la ciudad de Nueva York a Los Ángeles,¿cuánto tiempo se necesitaría? ¿Cómo cam-biaría tu viaje si volaras? Cuando planeas unviaje de vacaciones, es útil estimar antes eltiempo de viaje. El tiempo de viaje depende delvehículo que usas, qué tan rápido viajas, la ruta


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Movimiento, fuerzas y máquinas simples T7


que tomes y hasta el terreno. Por ejemplo,manejar sobre montañas escabrosas puedellevar más tiempo que manejar por regionesagrícolas planas. Con esta información, puedesplanear tu viaje de tal manera que llegues atiempo a tu destino final. Formula una hipótesissobre cuál es la forma más rápida de viajar.

Metas■ Investigar tiempos de viaje.■ Comparar tiempos de viaje en diferentes

medios de transporte.■ Evaluar la manera más rápida de viajar entre

dos puntos.■ Diseñar una tabla para mostrar tus hallazgos

y comunicarlos a otros alumnos.

Fuente de datosVisita red.msscience.com/internet_lab para más

información sobre tiempos de viaje, medios detransporte, distancias entre lugares y datos deotros estudiantes.

Diseña un plan1. Escoge un punto inicial y un destino final.2. Identifica las rutas que se usan común-

mente entre esas dos localidades.3. Estudia los medios comunes de viajar entre

esas dos localidades.4. Investiga cómo estimar el tiempo de viaje.

¿Qué factores pueden hacer que tu viajedure más o menos tiempo?

Sigue tu plan1. Asegúrate de que tu maestro(a) apruebe tu

plan antes de comenzar.2. Calcula el tiempo de viaje y la distancia

entre tus dos localidades usando diferentesmedios de transporte.

Analiza tus datos1. Analiza los datos que anotaste en tu Diario

de ciencias para determinar el método másrápido de viajar. ¿Qué es mejor, manejar ovolar? ¿Investigaste otro método de viaje?

2. Calcula la velocidad promedio para losmedios de transporte que investigaste. ¿Cuáles el más rápido? ¿Cuál es el más lento?

3. Haz una tabla que compare el tiempo deviaje, la rapidez promedio y las distancias delos diferentes métodos de viaje. ¿Cuál es elmétodo más rápido? ¿Es este siempre el másconveniente? ¿Qué factores aumentan eltiempo de viaje?

4. Comparte tus datos poniéndolos en el sitioWeb de Glencoe Science.

Concluye y aplica1. Compara tus hallazgos con los de tus com-

pañeros y con los datos publicados en elsitio Web de Glencoe Science. ¿Cuál fue lamayor distancia investigada? ¿La menor?

2. ¿Qué factores pueden afectar el tiempo deviaje de cada medio? ¿Cómo variaría tutiempo de viaje si no hubieras tenido unvuelo directo?

3. Infiere cómo el promedio de velocidad deun vuelo cambiaría si en el tiempo total deviaje incluyeras la ida y el regreso al aerop-uerto y los tiempos de espera.

Comunica tus datosHalla este laboratorio usando el enlace red.msscience.com/internet_lab. Publica tusdatos en la tabla provista. Combina tus datoscon los de otros estudiantes y haz un cuadernode viajes que estime el tiempo de viaje paravarias localidades alrededor del mundo.

Guía de estudio

Sección 1 El movimiento1. La velocidad promedio es la distancia reco-

rrida dividida por el tiempo: s � d/t2. Un objeto está acelerando cuando su veloci-

dad y/o dirección de movimiento cambia.3. La aceleración puede calcularse al dividir el

cambio de velocidad por el tiempo.

Sección 2 Las leyes del movimiento de Newton1. Inercia es una medida de la dificultad para

alterar el movimiento de un cuerpo.

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2. La primera ley de Newton establece que uncuerpo permanecerá en reposo o movién-dose con velocidad constante si no actúaninguna fuerza sobre él.

3. La segunda ley de Newton describe la mane-ra en que las fuerzas desequilibradas o lasfuerzas netas actúan sobre un cuerpo. Elcuerpo acelerará de acuerdo con Fnet = ma.

4. La tercera ley de Newton establece que lasfuerzas actúan en pares iguales peroopuestos.

Sección 3 Trabajo y máquinas simples1. Se hace trabajo cuando una fuerza hace que

un cuerpo se mueva en la dirección de lafuerza. El trabajo es igual a la fuerza aplicadamultiplicada por la distancia sobre la que seaplica la fuerza.

2. Una máquina es un instrumento que hacemás fácil el trabajo. Una máquina simplefacilita el trabajo con un movimiento. Unamáquina puede aumentar la fuerza, aumen-tar la distancia o cambiar la dirección de lafuerza aplicada. ¿Cómo facilita el trabajo estapalanca?

3. Ventaja mecánica es la fuerza de resistenciadividida por la fuerza de esfuerzo.

4. Los seis tipos de máquinas simples son:plano inclinado, cuña, tornillo, palanca,rueda y eje, y polea. Una máquina com-puesta está hecha de máquinas simples.


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Teacher Guide& Answers

Hands-On ActivitiesMiniLAB: Try at Home (page 3)

1. Answers will vary.2. Answers will vary.3. Answers will vary.

MiniLAB: (page 4)1. Students will observe that it is nearly impossible

to prevent the sticks from being pulled together.2. The more times the rope is wrapped around the

sticks, the harder it is to keep the sticks frombeing pulled together.

Lab (page 5)Lab Preview1. flat surface2. for at least 5 s to 10 s

Conclude and Apply1. The ball slows down and comes to a stop.2. Gravity and static friction; because the ball’s

motion did not change, no unbalanced force wasacting on it.

3. Gravity and rolling friction; friction was theunbalanced force that caused the motion of theball to change.

Lab: Use the Internet (page 7)Analyze Your Data1. Answers will be subjective and based on the

students’ individual research.2. Remind students that speed is calculated by

dividing distance traveled by amount of time forthe trip.

3. Students might conclude that the fastest methodmight not always be the most convenient. Factorssuch as flight schedules may influence their decisions.

Conclude and Apply1. Answers will vary based on each student’s

individual research.2. Weather conditions and time of day can affect

travel times. Layovers can significantly add totravel time.

3. Average speed would decrease, as the time spenttraveling to and from airports as well as waitingtime can be significant.

Laboratory Activity 1 (page 9)Data and ObservationsTables 1 and 2 should show most or all marks in thelast column, indicating both marbles fell at the samespeed.

Questions and Conclusions1. Students should find that the speeds are similar.2. If the gutter is level, there should not be any

apparent difference in speed.3. Answers will vary. It is important to find out that

position in the gutter is not a factor in regard tospeed.

4. Students should find the results are the same nomatter what the angle.

5. Objects of different mass fall at the same rate ofspeed.

6. Answers may vary but should include that thefriction of the ramp will slow the marbles morethan the friction of the air will.

Laboratory Activity 2 (page 13)Data and ObservationsAnswers will vary depending on the accuracy of stu-dent measurements.

Questions and Conclusions1. the hand pulling on the brick2. The force needed to start the brick is greater than

the force needed to keep the brick in motion.3. The greater the mass of the brick, the greater the

force needed to keep the brick in motion.4. The greater the mass of a body, the greater the

force needed to start a body in motion.5. friction6. The person inside the bus is moving with the

speed of the bus. When the bus stops, the personwill continue to move forward because of inertia.

Meeting Individual NeedsDirected Reading for Content Mastery (page 17)

Overview (page 17)1. 8 km/h2.

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Teacher Guide & Answers (continued)

3. action force4. The box will collapse.5. They increase the distance over which the force is

applied, so you don’t need as much force.

Sections 1 and 2 (page 18)1. 120 m + 90 m + 50 m + 70 m = 330 meters2. 330 m ÷ 2 min = 165 meters per minute3. speed4. speed5. acceleration6. net force7. accelerate8. opposite

Section 3 (page 19)

1. Force must be applied to an object and thatobject must move in the direction of the appliedforce to perform work.

2. A simple machine is one that has only one part.3. √4. An inclined plane allows you to lift a heavy load

by using less force over greater distance.

Key Terms (page 20)1. force2. motion3. acceleration4. velocity5. joules6. output force7. average speed8. friction9. lever

10. net force

Lectura dirigida para Dominio del contenido (pág. 21)Sinopsis (pág. 21)1. 8 km/h 2.

3. acción fuerza4. La caja se hundirá.5. Aumentan la distancia sobre la cual se aplica la

fuerza, de modo que no necesitas tanta fuerza.

Secciones 1 y 2 (pág. 22)1. 120 m + 90 m + 50 m + 70 m = 330 metros2. 330 m ÷ 2 min = 165 metros por minuto3. rapidez4. rapidez5. aceleración6. fuerza neta7. acelera8. opuesto

Sección 3 (pág. 23)

1. La fuerza se debe aplicar al cuerpo y ese cuerpodebe moverse para realizar trabajo.

2. Una máquina simple es aquella que sólo consta deuna parte.

3. X4. Un plano inclinado te permite levantar una carga

pesada al usar menos fuerza a lo largo de una dis-tancia mayor.

Términos claves (pág. 24)1. fuerza2. movimiento3. aceleración4. velocidad

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5. julios6. fuerza de salida7. rapidez promedio8. fricción9. palanca

10. fuerza neta

Reinforcement (page 25)Section 1 (page 25)

1. acceleration2. speed at a given time3. average speed4. distance traveled5. 25 cm/min6. 5 cm/min2

7. 10 cm/min8. 30 cm9. 0

10. it accelerates11. (0 cm/min – 25 cm/min)/2 min = 12.5 cm/min2

12. negative acceleration

13. 1 (12.5)(2)2 = 25 cm2

Section 2 (page 26)1. a. third law

b. first lawc. second lawd. first lawe. second lawf. third law

2. 03. friction4. a = Fnet/m

a = (0.2 N)/(0.25 kg) = 0.8 m/s2

5. The yo-yo will not accelerate as quickly; the largerthe mass, the smaller the acceleration for the sameamount of force.

6. 0.001 N

Section 3 (page 27)1. no work2. no work3. work4–5. The object does not move. The object does not

move in the same direction as the force.6. You must apply force to an object, and the

object must move in the same direction as theforce you apply.

7. Work is measured in joules, Students may givethe formula, 1 J = 1 N • m

8. the number of times a force is multiplied9. They depend on the position of the fulcrum and

the effort force and resistance force. In a first-class lever, the fulcrum is between the effortforce and resistance force. In a second-classlever, the resistance force is in the middle. In athird-class lever, the effort force is in the middle.

10. It changes the direction of the force.

Enrichment (page 28)Section 1 (page 28)

1–3. Answers may include billowing clothing,depicting two or more versions of the character inthe same panel as, for instance, the characterswings on a vine, or over several panels showingpeople frozen in the background as the characterraces past.Cartoon panels: Answers will vary. Panel 1 may present Car A behind Car B, in panel 2 they maybe even, and in panel 3 Car A may be pullingahead. Students may include long vertical motionlines to simulate speed. They may even change theshape of the car to show that one is “workingharder” to pass the other.

4. The first, constant motion, represents the formulaspeed = d/t.The second, accelerating motion, represents the formula a = (final speed – initial speed)/t.

Section 2 (page 29)1. Newton’s second law of motion2. The ball would continue moving in a straight line

until another force, such as the bat or gravity,changed its direction. The force and accelerationboth come from the same place—the point ofimpact on the bat.

3. Answers will vary.

Section 3 (page 30)1. 5:12. 2:13. 2:14. 1:15. Gear d has the lowest ratio. It would be the best

gear for riding uphill.

Note-taking Worksheet (page 31)Refer to Teacher Outline, student answers areunderlined.

AssessmentChapter Review (page 35)

Part A. Vocabulary Review (page 35)1. acceleration (2/1)2. mass (5/2)3. work (7/3)4. average speed (3/1)5. velocity (1/1)6. force (4/2)7. ramp (8/3)8. friction (5/2)9. instantaneous speed (1/1)

10. mechanical advantage (9/3)11. net force (4/2)12. inertia (4/2)13. laws of motion (4/2)

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Part B. Concept Review (page 36)1. simple machine (8/3)2. speed, direction (1/1)3. resistance (9/3)4. velocity (2/1)5. instantaneous (1/1)6. easier (5/2)7. different (6/2)8. mass (5/2)9. direction (9/3)

10. slows (2/1)11. smaller (4/2)12. the force (5/2)13. 35 N (4/2)14. force (7/3)15. a.125 m/5 s = 25 m/s (3/1)

b. (50 m/s)/5 s = 10 m/s2 (3/1)c. (10 m/s2) ✕ 3 s = 30 m/s (3/1)d. 1/2(10 m/s2)(4 s)2 = 80 m (3/1)

Chapter Test (page 37)I. Testing Concepts (page 37)1. a (4/2)2. c (4/2)3. a (6/2)4. d (4/2)5. d (2/1)6. b (4/2)7. d (2/1)8. d (3/1)9. c (2/1)

10. a (8/3)11. b (4/2)12. b (1/1)13. b (5/2)14. d (9/3)15. c (6/2)16. true (1, 2/1)17. true (9/3)18. true (8/3)19. false; Average speed does include the time a car

sits at red lights on the way home. (3/1)20. false; There is usually less friction on a smooth

surface. (4/2)21–30. Force—23, 24, 28, 29, and 30

Not a force—21, 22, 25, 26, and 27 (4/2)

II. Understanding Concepts (page 39)1. 8 m/s (3/1)2. 8 m/s (3/1)3. 5 m/s2 (3/1)4. a. C (3/1)

b. B (3/1)5. slows down (4/2)6. reaction or direction (4/2)7. accelerates (4/2)

8. Answers will vary. One possible experiment woulduse the board as an inclined plane to consistentlyaccelerate the marble. Materials at the base of theboard could include concrete, linoleum, carpet,water, metal, wood, or sand. An accurate means ofmeasuring time would also be necessary. (4/2)

III. Applying Concepts (page 40)1. s = d/t = 210 km/3 = 70 km/h (3/1)2. d = s ✕ t = 60 km/h ✕ 6 h = 360 km (3/1)3. F = m ✕ a; 20 = m ✕ 2; m = 20/2 = 10 kg (5/2)4. a = (final speed – initial speed)/t = 20 – 0/5 =

4 m/s2 (5/2)5. W = F ✕ d = 400 N ✕ 2 m = 800 N m = 800 joules

or 800 J (7/3)

IV. Writing Skills (page 40)1. Gravity acts on the arrow, causing it to fall.

Students may also know that air friction slows thearrow. (4/2)

2. Inertia is a tendency to resist a change in motion.Students may know that inertia is the measure ofan object’s ability to stay at rest or to keep inmotion. (4/2)

Section Focus Transparency 1 (page 42)

It Must Be MathTransparency Teaching Tips■ Ask the students why it’s important to know

your speed while driving a car. The speedometerdisplay is connected to the transmission and computes speed relative to the turning rate of thedriveshaft. Explain the practical elegance of beingable to compute the movement of real objectsusing numbers.

■ Ask students to explain what Hobbes means inthe second panel of the cartoon strip.

■ Provide the students the following data and askthem to find the final speed in miles per hour.The distance traveled was 450 feet; the time wasten seconds. Remind them that after findingfeet/second, they will have to change it tomiles/hour. Tell them that they will need to complete four steps to solve the problem.(450 ÷ 10 = 45; 45 ✕ 60 = 2,700; 2,700 ✕ 60 =162,000; 162,000 ÷ 5280 = 30.68, or around 31miles per hour.) Using metrics and a distance of137 meters, the math is as follows: 137 ÷ 10=13.7× 60 = 822; 822 × 60 = 49,320; 49,320 ÷ 1000 =49.32, or around 49 kilometers per hour. Makethis as fun and easy as possible.

Content Background■ Besides driving, measuring speed is important in

all forms of transportation. It is also used in predicting weather, numerous athletic events, andin science.

■ In luge, a form of sledding, speeds greater than 120 km/h (75 mph) have been attained.

■ Speed equals distance traveled divided by time.


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Answers to Student Worksheet1. The cartoon mentions a speedometer and

dividing distance by time.2. The speedometer is best for getting the speed at a

specific instant. On the other hand, average speed(distance divided by time) tells you which sleddescended the hill more quickly.

3. Friction and some air resistance stop the sled.


Bird’s Eye ViewTransparency Teaching Tips■ You may use this transparency to introduce gravity

as a force. According to Newton’s law of gravitation,every object in the universe attracts every otherobject (the exact mechanics at the atomic level arenot yet understood). Tell the students that thegreater the mass of the attracting object, the moreforce is applied. Drop a small book and a ruler andhave students observe. Ask them why they landed atthe same time. (The Earth’s gravitational pull isconstant, the same for both.)

■ Ask the students whether skydivers fall at ever-increasing speeds or at a constant rate as theyhurtle earthward.

■ Ask the students why body position affects rate ofdescent (surface area exposed to air resistance).

Content Background■ The gravitational attraction (force) between two

bodies is proportional to the mass of each, varyinginversely to the square of the distance betweenthem.

■ On Earth, a falling object accelerates from a restingposition to terminal velocity, which is the fastestfree-fall velocity. A skydiver accelerates in thedirection of the force, or toward Earth. Terminalvelocity for a skydiver is around 193 meters persecond.

■ Earth’s gravitational force keeps the Moon inorbit. This force is actually causing the Moon tofall, not toward the Earth but from the straightline it would travel if gravity were not at work.

■ The first verifiable parachute jump was success-fully completed in 1797 by the Frenchman Andre-Jacques Garnerin. He jumped from a balloon 1,000 meters (almost 3,300 feet) overParis.

Answers to Student Worksheet1. The skydivers fall with increasing speed, attracted

by the gravitational pull of Earth. Opening theparachute slows the rate of descent and allows theskydivers to land safely.

2. Opening the parachute causes an acceleration,slowing the skydivers’ fall. If a skydiver changesdirection during a fall, that is another acceleration.

3. They fall at the same rate because the gravitationalpull of Earth is constant (the same for everyone).


Movin’ OnTransparency Teaching Tips ■ You may use this transparency to introduce sim-

ple machines. Point out and briefly explain the sixsimple machines—lever, pulley, wheel and axle,inclined plane, screw, and wedge.

■ Ask the students to identify the simple machinesat work in the transparency. (They are theinclined plane, lever, and wheel and axle; perhapsa pulley is used on the rear sliding door.)

■ Have the students identify other machines in theirdaily lives, such as bicycles, garage doors, skate-boards, etc.

Content Background■ The wedge was probably the earliest tool, edged

rocks being used by prehistoric people to splitbones.

■ A lever-balance device was probably used in Egyptabout 5000 B.C. The inclined plane may date toabout the same time.

■ The wheel has been dated to Sumeria, around3500 B.C. The spoked wheel and axle date to AsiaMinor, around 2000 B.C.

■ In the third century B.C., Archimedes supposedlypulled a boat from the water using a compoundpulley.

■ The Greeks may have been the first to use thescrew, using it to press clothes in the second cen-tury B.C. One hundred years later, the screw wasbeing used to press oil and wine.

Answers to Student Worksheet1. The ramp and the dolly are helping the mover get

the boxes out of the truck.2. There are wheels on the truck and wheels on the

dolly.3. Answers will vary. Students will probably mention

the ramp and dolly. Other possibilities includetools like hammers and screwdrivers for takinglarge items apart. Encourage discussion of toolsthat make work easier.

Teaching Transparency (page 45)


Section 2Transparency Teaching Tips■ Use the transparency to introduce the concept that

motion occurs in predictable ways. Tell studentsthat in the 1600s, Isaac Newton developed threelaws of motion that helped to describe and predicthow everyday objects move.

■ Ask students to identify the forces at work in thetransparency. Remember to identify opposingpairs of forces. For example, if students say thehockey stick pushed the ball, they should alsoindicate the ball exerted a force on the stick.

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Reteaching Suggestion■ Review with students the three laws of motion

and describe how the pictures on the transparencyillustrate these laws.

ExtensionsActivity: In pairs, have students devise an activitythat demonstrates one of the laws of motion.Students should conduct the activities for the class.Challenge: Have students cut pictures from anewspaper or magazine that show objects inmotion. Ask pairs of students to diagram andexplain the forces at work on the objects in two ofthe pictures.

Answers To Student Worksheet1. You can infer the forces are unbalanced.2. a push from the hockey stick; friction with the

ground3. The shopping cart will accelerate more because it

has less mass.4. Newton’s third law of motion5. the ground6. The forces don’t cancel each other out because

they do not act on the same object. In this case,one force acts on the wall, and the other acts onthe swimmer. The swimmer accelerates becauseshe is experiencing unbalanced forces.

Assessment Transparency (page 47)


Section 3Answers1. A. Students must realize that the railroad tracks

exert a force opposite in direction to the forceexerted by the train on the tracks.

2. G. To answer this question, students must remember that friction is the force that resistsmotion between two surfaces in contact; frictionacts opposite to the direction of motion. As it isdrawn, the train is moving forward, so the force offriction must be indicated by arrow 2.

3. C. Forces indicated by arrows 2 and 4 are pointingin opposite directions, so, if they are the samesize, they are balanced. Balanced forces do notcause a change in an object’s motion.Choice A: No, accelerating the train is a change inmotion.Choice B: No, decelerating the train is also achange in motion.Choice C: Yes, the train will keep constant motionon a straight track.Choice D: No, this is similar to decelerating.

Test-Taking TipRemind students to read each question carefully tobe sure they understand what is being asked.


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