force and newton’s laws -...

Glencoe Science

Chapter Resources

Force and Newton’s Laws

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: Leroy Simon/Visuals Unlimited;Section Focus Transparency 2: UNIVERSAL PRESS SYNDICATE;Section Focus Transparency 3: Wally McNamee/CORBIS,Teaching Transparency: (t) Globus Brothers Studios, New York, (b) Stone

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 theForce and Newton’s Laws program. Any other reproduction, for use or sale, isprohibited without prior written permission of the publisher.

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

ISBN 0-07-867154-X

Printed in the United States of America.

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

Force and Newton’s Laws 1

ReproducibleStudent Pages

Reproducible Student Pages■ Hands-On Activities

MiniLAB: Try at Home Observing Friction . . . . . . . . . . . . . . . . . . . . . 3MiniLAB: Measuring Force Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Lab: Balloon Races . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Lab: Design Your Own Modeling Motion in Two

Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Laboratory Activity 1: Static and Sliding Friction . . . . . . . . . . . . . . . . 9Laboratory Activity 2: Newton’s Second Law . . . . . . . . . . . . . . . . . . . 13Foldables: Reading and Study Skills. . . . . . . . . . . . . . . . . . . . . . . . . . 17

■ Meeting Individual NeedsExtension and Intervention

Directed Reading for Content Mastery . . . . . . . . . . . . . . . . . . . . . . . 19Directed Reading for Content Mastery in Spanish . . . . . . . . . . . . . . 23Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Enrichment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Note-taking Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

■ AssessmentChapter Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Chapter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

■ Transparency ActivitiesSection Focus Transparency Activities . . . . . . . . . . . . . . . . . . . . . . . . 44Teaching Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Assessment Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

2 Force and Newton’s Laws

Hands-OnActivities

Hands-On Activities

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Observing FrictionProcedure 1. Lay a bar of soap, a flat eraser, and a key side by side on one end of a hard-sided notebook.

2. At a constant rate, slowly lift the end of the notebook with objects on it. Note the order inwhich the objects start sliding. Record your observations in the table.

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Data and Observations

Analysis1. For which object was static friction the greatest? For which object was it the smallest? Explain,

based on your observations.

2. Which object slid the fastest? Which slid the slowest? Explain why there is a difference inspeed?

3. How could you increase and decrease the amount of friction between the two materials?

Bar of Soap

Eraser

Key


Name Date Class

Measuring Force PairsProcedure 1. Work in pairs. Each person needs a spring scale.

2. Hook the two scales together. Each person should pull back on a scale. Record the two readings in the table below. Pull harder and record the two readings.

3. Continue to pull on both scales, but let the scales move toward one person. Do the readingschange?

4. Try to pull in such a way that the two scales have different readings.


Hands-On Activities

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Analysis1. What can you conclude about the pair of forces in each situation?

2. Explain how this experiment demonstrates Newton’s third law.

Set-up Scale 1 Scale 2

both partnersFirst pull pull

both partnersSecond pull pull harder

scales closer toThird pull one person

Fourth pull

Fifth pull

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Lab PreviewDirections: Answer these questions before you begin the Lab.1. What does Newton’s third law of motion state?

2. What will you use to make a path for your rocket?

The motion of a rocket lifting off the launch pad is determined by Newton’slaws of motion. Here you will make a balloon rocket that is powered byescaping air.

Real-World QuestionHow do Newton’s laws of motion explain the motion of balloon rockets?

Materialsballoons string *clockdrinking straws tape *Alternate materials

meterstick stopwatch

Goals■ Measure the speed of a balloon rocket.■ Describe how Newton’s laws explain a rocket’s motion.

Balloon Races

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Safety Precautions

Procedure1. Make a rocket path by threading a string

through a drinking straw. Run the stringacross the classroom and fasten at both ends.

2. Blow up a balloon and hold it tightly at theend to prevent air from escaping. Tape theballoon to the straw on the string.

3. Release the balloon so it moves along thestring. Measure the distance the balloontravels and the time it takes.

4. Repeat steps 2 and 3 with different balloons.


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Hands-On ActivitiesCommunicating Your Data

Discuss with classmates which balloon rocket traveled the farthest. Why? For more help,refer to the Science Skill Handbook.

Analyze Your Data1. Compare and contrast the distances traveled. Which rocket went the greatest distance?

2. Calculate the average speed for each rocket. Compare and contrast them. Which rocket has thegreatest average speed?

Conclude and Apply1. Infer which aspects of these rockets made them travel far or fast.

2. Draw a diagram on a separate sheet of paper showing all the forces acting on a balloon rocket.

3. Use Newton’s laws of motion to explain the motion of a balloon rocket from launch until itcomes to a stop.

(continued)

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Lab PreviewDirections: Answer these questions before you begin the Lab.1. What is a net force?

2. What safety precautions must you take for this Lab?

When you move a computer mouse across a mouse pad, how does the rollingball tell the computer cursor to move in the direction that you push themouse? Inside the housing for the mouse’s ball are two or more rollers thatthe ball rubs against as you move the mouse. They measure up-and-downand back-and-forth motions. The motion of the cursor on the screen is basedon the movement of the up-and-down rollers and the back-and-forth rollers.

Real-World QuestionCan any object be moved along a path by aseries of motions in only two directions?

Form a HypothesisHow can you combine forces to move in astraight line, along a diagonal, or around corners? Place a golf ball on something thatwill slide, such as a plastic lid. The plastic lid is called a skid. Lay out a course to follow onthe floor. Write a plan for moving your golfball along the path without having the golfball roll away.

Possible Materialsmasking tapestopwatch*watch or clock with a second handmeterstick*metric tape measurespring scales marked in newtons (2)plastic lidgolf ball*tennis ball*Alternate materials

Goals■ Move the skid across the ground using two

forces.■ Measure how fast the skid can be moved.■ Determine how smoothly the direction can

be changed.

Safety Precautions

Test Your HypothesisMake a Plan1. Lay out a course that involves two directions,

such as always moving forward or left.2. Attach two spring scales to the skid. One

always will pull straight forward. Onealways will pull to one side. You cannotturn the skid. If one scale is pulling towardthe door of your classroom, it must alwayspull in that direction. (It can pull with zeroforce, if needed, but it can’t push.)

3. How will you handle movements alongdiagonals and turns?

4. How will you measure speed?

Design Your Own

Modeling Motion in Two Directions

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5. Experiment with your skid. How hard doyou have to pull to counteract sliding frictionat a given speed? How fast can you accelerate?Can you stop suddenly without spilling thegolf ball, or do you need to slow down?

6. Write a plan for moving your golf ballalong the course by pulling only forward orto one side. Be sure you understand yourplan and have considered all the details.

Follow Your Plan1. Make sure your teacher approves your plan

before you start.2. Move your golf ball along the path.3. Modify your plan, if needed.4. Organize your data so they can be used

to run your course and write them on a separate sheet of paper.

5. Test your results with a new route.

Hands-On Activities

Communicating Your Data

Compare your conclusions with those of other students in your class. For more help,refer to the Science Skill Handbook.

Analyze Your Data1. What was the difference between the two routes? How did this affect the forces you needed to

use on the golf ball?

2. How did you separate and control variables in this experiment?

3. Was your hypothesis supported? Explain.

Conclude and Apply1. What happens when you combine two forces at right angles?

2. If you could pull on all four sides (front, back, left, right) of your skid, could you move anywherealong the floor? Make a hypothesis to explain your answer.

(continued)

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Static and Sliding Friction

When two objects are in contact, the molecules on one surface can attract molecules on the othersurface. These surfaces are not smooth; small bumps and grooves exist. When one object slides overthe other, the surfaces catch and stick as these bumps and grooves nestle together. The force thatresults between the surfaces is called friction. Many factors affect the force of friction, including thematerials the surfaces are made from, how smooth the surfaces are, and how hard the surfaces arepressed together. For a block sliding on a level horizontal surface, the weight of the block pushesthe bottom surface of the block against the horizontal surface.

When an object is at rest, static friction must be overcome to move the object. When one objectis already sliding over another, sliding friction occurs. To keep the object moving, a force must beapplied that is equal to the sliding friction force.

StrategyYou will calculate coefficients of static and sliding friction.You will compare static friction to sliding friction.You will describe the effect of weight on the force of friction.You will determine the effect of surface area on friction.

Materialseye hook spring scale calibrated in newtonsset of masses wood block (about 5 cm ✕ 10 cm ✕ 26 cm)

LaboratoryActivity11

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Procedure 1. Screw the eye hook into the end of the

block. Weigh the wood block and eye hookusing the spring scale. Record the weight inthe table.

2. Lay the wood block on a flat surface asshown in Figure 1.

3. Find the force required to move the blockfrom rest. Pull on the spring scale andnotice the highest reading that occursbefore the block moves. That is the staticfriction force.

26 cm

Eye hook

Spring scale

10 cm

5 cm

Figure 1


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Laboratory Activity 1 (continued)

Name Date Class

4. Find the force required to keep the blockmoving at a constant speed. As you pull onthe spring scale, the reading will not beexact because the friction value will vary.Make the best judgment you can for thevalue of sliding friction. Record this value in the table.

5. Repeat steps 3 and 4 with different weightsadded on top of the friction block. Be sureto record the new weight of the block andits added weight.

6. Repeat steps 3 and 4 without masses addedand with the block resting on a side with adifferent area.

7. Calculate the coefficient of static frictionfor each of the trials using the followingequation.

µstatic = static friction forceweight

8. Calculate the coefficient of sliding friction foreach of the trials using the equation below.

µsliding = sliding friction forceweight

9. Graph the relationship between the weightof the block and the force of static frictionin Graph 1. Also graph the relationshipbetween the force of sliding friction andthe weight of the block in Graph 1.


Table 1

Hands-On Activities

Force ofstatic friction

Force ofsliding friction

Weightof block �Static �Sliding

Areaof side

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Questions and Conclusions1. How did the addition of more weight affect the friction?

2. How did the change in surface area of the contact between the block and the table affect thefriction?

3. How did the force of friction depend on the weight of the block?

4. Compare the size of static friction and sliding friction.

Fric

tion

forc

e (N

)

Weight (N)

00 1 2 3 4 5 6

0.5

1

1.5

2.0

2.5

Weight Versus Friction ForceGraph 1


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5. What could be a source of error in this experiment?

6. What happened to the coefficients of friction as the weight increased?

7. What happened to the coefficients of friction as the surface area of the contact increased?

8. Does the coefficient of sliding friction depend on the weight of the block? Explain.

9. Does the area of contact between objects make a difference in the friction forces? Explain howyou know.

10. If you are buying new tires for a car, would you prefer a high or a low coefficient of friction?

Strategy Check

Can you calculate coefficients of static and sliding friction?

Do you understand the effects of weight and surface area on the force of friction?

Hands-On Activities

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Newton’s Second Law

Newton’s second law of motion deals with acceleration, which is how quickly something speedsup or slows down. Acceleration depends on the mass of an object and the force pulling or pushingit. One way to write Newton’s second law is force = mass ✕ acceleration. Another way to think ofNewton’s second law is that if the same force acts on two objects, the object with the greater masswill accelerate more slowly.

StrategyYou will time the acceleration of a small toy car.You will observe the effects of increasing mass on acceleration.

Materialsbalance modeling clay (about 300 g) string or threadlarge table small toy car with free-spinning wheels tapemeterstick stopwatch

Procedure 1. Cut a piece of string or thread 110 cm long.

Tie a small loop in one end of the string.2. Make a small ball of clay with a mass of

about 2.5 g. Attach this ball of clay to thestring by folding the clay around the loop.The loop will prevent the clay ball fromfalling off the string.

3. Divide the remaining clay into 40-g pieces.4. Use your balance to measure the mass of

the toy car. Write the mass of the car in theData and Observations section.

LaboratoryActivity22

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Clay ball

Tape

Toy car

String

1 m

Figure 1


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5. Use a meterstick to find a spot on the table1 m from the edge. Mark it with a smallpiece of tape. This spot will be the startingpoint for the toy car during the experiment.

6. Put the front of the toy car at the starting point.Hold the piece of string on the table so that theclay ball is about 3 cm over the edge. Tape theother end of the string to the front of the toycar. Trim any excess string so that it does notinterfere with the car’s wheels. Check that yoursetup is similar to that shown in Figure 1.

7. Pick someone in your group to be the timer,someone to be the recorder, someone to holdthe toy car in place and release it, and some-one to catch it as it falls off the table.

8. Release the car. Use a stopwatch to measurethe time it takes for the car to reach thetable edge.

9. Write the travel time in Table 1.10. Repeat steps 8 and 9 two more times. Use

the data to calculate the average traveltime for the car.

11. Add one 40-g piece of clay to the top ofthe car. Be careful that the clay does notinterfere with the car’s ability to roll freely.

12. Time three trips of the car. Record thetravel times, calculate the average time,and record the average time in Table 1.

13. Repeat steps 11 and 12 until you havetimed the car carrying 160 g of clay.

Hands-On Activities


Mass of car = ______ g

Table 1

Mass (g) Travel Time (s)

Total clay on Total car Time 1 Time 2 Time 3 Average timetop of car and clay (T1) (T2) (T3) (T1 � T2 � T3) / 3

0

40

80

120

160

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Graph 1

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Tota

l mas

s (g

)

Average travel time (s)

Questions and Conclusions1. Make a graph of total mass versus time in Graph 1.

2. Explain how your data support Newton’s second law of motion.

3. Why is it important to average three travel times for each one of the total masses?

4. What were some possible sources of error in this lab? In other words, what things might havecaused differences in travel time for the same mass?


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5. Use your graph to predict how much mass would be necessary to cause travel time of 15 s.Test your prediction. What happened?

Strategy Check

Do you understand the effects of increasing mass in acceleration?

Can you relate force, mass, and acceleration?

Hands-On Activities

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

Newton’s Three Laws of Motion

First Law of Motion

Second Law of Motion

Third Law of Motion

This law connects force, acceleration, and mass. It states that an objectacted upon by a net force will accelerate in the direction of the force.

This law describes how an object moves when no net force is acting onit. It states that unless a net force acts on it, an object at rest tends tostay at rest and a moving object will continue moving in a straight linewith constant speed.

This law describes the connection between the object supplying theforce and the object receiving the force. It states that forces always actin equal but opposite pairs.

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Meeting IndividualNeeds

Meeting Individual Needs

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OverviewForce and Newton’s Laws

Directions: Complete the concept map using the phrases listed below.

the direction of the force a net force an equal but opposite reaction

Mee

ting

Indi

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eeds

Directed Reading for

Content Mastery

Newton’s laws of motion

the second law the third lawthe first law

which states that anobject at rest or moving

at constant speed in a straight path will

continue to do so untilacted upon by

which states that anobject acted

upon by a net forcewill accelerate in

which states that forevery action there is

3.2.1.

Directions: In the space provided, write the number for Newton’s law of motion that best applies to the conditions described.

4. A golf ball is motionless until it is hit by a golf club.

5. The golf club is swung in a northerly direction, and that is the directionthe ball travels.

6. When hit, the golf ball pushes back on the club with the same amountof force that the club exerts on the ball.

Name Date Class


Section 1 ■ Newton’s First LawSection 3 ■ Newton’s Third Law

Directions: Identify which one of Newton’s laws applies in each case. Explain your answers.

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2.

1.


Content Mastery

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Section 2 ■ Newton’s Second Law

Directions: Write the correct term in the boxes in the puzzle. The boxed letters should spell the word that completes Newton’s Second Law in item 9.

Mee

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eeds

1. ______ exists between any two objects that have mass.

2. ______ occurs any time an object speeds up, slows down, or changes direction.

3. In the formula a =Fnet, Fnet stands for ______.m

4. When you sit in a chair, it exerts ______ against you.

5. Force is measured in ______.

6. A gravitational ______ exists between you and every object in the universe.

7. In the formula a =Fnet, m stands for ______.m

7

6

5

4

3

2

11

8

E

E

8. ______ describes how fast an object is moving and in what direction.

9. An object acted upon by a force will _____________ in the direction of the force.


Content Mastery

Name Date Class


Key TermsForce and Newton’s Laws

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

normal force friction inertia force

net force second law third law acceleration

1. When more than one force is acting on an object, the

______ determines the motion of the object.

2. When you throw a ball, your hand applies ______ to the ball.

3. _____ is the force that brakes use to stop a car.

4. _____ tells how velocity changes.

5. If an object is placed on a flat surface, the _____ is

straight up and is equal to the weight of the object.

6. “Forces always act in equal but opposite pairs” is Newton’s

_____ of motion.

7. Every time you change your speed or direction, Newton’s

_____ describes the action.

8. The tendency of an object to remain at rest is called _____.

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Content Mastery

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Nombre Fecha Clase

Las fuerzas y las leyes de Newton 23

SinopsisLas fuerzas y las leyes de Newton

Instrucciones: Completa el mapa de conceptos usando las siguientes frases.

la dirección de la fuerza una fuerza neta una reacción igual, pero opuesta

Lectura dirigida para

Dominio del contenidio

Las leyes demovimiento de Newton

la segunda ley la tercera leyla primera ley

establece que un cuerpo enreposo o en movimiento a unavelocidad constante, en una

trayectoria recta, permaneceráasí a menos que una fuerza

actúe sobre él

establece que uncuerpo sobre el cual

actúa una fuerzaneta, acelerará en

que establece quepor cada acción

existe

3.2.1.

Instrucciones: En el espacio dado, escribe el número de la ley de movimiento de Newton que mejor se aplica alas condiciones descritas.

4. Una pelota de golf está en reposo hasta que se golpea con un palo de golf.

5. El palo de golf se oscila en dirección norte y esa es la dirección en queviaja la pelota.

6. Al golpearse, la pelota de golf empuja el palo con la misma cantidad defuerza que el palo ejerce sobre ella.

Satis

face

las n

eces

idad

es in

divi

dual

es

Nombre Fecha Clase

24 Las fuerzas y las leyes de Newton

Sección 1 ■ Primera ley de NewtonSección 3 ■ Tercera ley de Newton

Instrucciones: Identifica cuál de las leyes de Newton se aplica en cada ejemplo. Explica tus respuestas.

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Satisface las necesidades individuales

1.

2.

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Nombre Fecha Clase

Las fuerzas y las leyes de Newton 25

Sección 2 ■ Segunda ley de Newton

Instrucciones: Escribe el término correcto para cada definición. Las letras en las cajas numeradas verticalmentedeben contener la palabra que completa el nombre de las leyes de Newton.

1. Cuando te sientas en una silla la silla ______ contra ti.

2. Un cuerpo sobre el cual se ejerce una fuerza, se ______ en la dirección de lafuerza.

3. Existe una fuerza gravitatoria entre ti y todos los objetos del ______.

4. ocurre siempre que un objeto aumenta su rapidez, la disminuye o cambia dedirección

5. En la fórmula a = , la m representa ______.

6. Te dice con qué rapidez se mueve un objeto y en qué dirección.

7. En la fórmula a = , la F representa ______.

8. existe entre dos cuerpos cualquiera que tienen masa

9. La fuerza se mide en ______.

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Nombre Fecha Clase

26 Las fuerzas y las leyes de Newton

Términos clavesLas fuerzas y las leyes de Newton

Instrucciones: Usa los siguientes términos para completar las oraciones.

fuerza normal fricción inercia fuerza

fuerza neta segunda ley tercera ley aceleración

1. Cuando más de una fuerza actúa sobre un cuerpo, el(la)

______ determina el movimiento del cuerpo.

2. Cuando lanzas una pelota, tu mano aplica un(a) sobre la

pelota.

3. Es la fuerza que usan los frenos para detener el auto.

4. El(La) ______ te dice los cambios en velocidad.

5. Si un objeto se coloca sobre una superficie plana, el(la)

______ es directamente hacia arriba y es igual al peso del

objeto.

6. “Las fuerzas siempre actúan en pares iguales pero

opuestos” es la ______ ley del movimiento de Newton.

7. Cada vez que cambias tu rapidez o dirección, la ______

de Newton describe la acción.

8. La tendencia de un cuerpo a permanecer en reposo se

llama ______.

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Satisface las necesidades individuales

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Newton’s First Law

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Directions: Mark each statement below either true or false. For each true statement, fill in all the correspond-ing numbers in the box above. When you’re done, you’ll find an important word from this chapter.

1. When the net force is zero, the forces on an object are balanced.

2. If two forces are in the same direction, they cancel each other out.

3. Any time the forces are unbalanced, an object will remain at rest.

4. According to Newton’s first law of motion, an object at rest will stay at rest until a netforce acts upon it.

5. According to Newton’s first law of motion, an object moving at a constant speed in a straight path will continue to do so until a net force acts upon it.

6. Friction brings most moving objects to a stop.

7. Friction will never speed up an object.

8. Galileo believed that the natural state of an object was to be at rest.

9. If you slide a bag of groceries along a countertop, you must first overcome rolling friction.

10. Walking would be impossible without rolling friction.

11. Rolling friction always reduces the net force acting against an object’s motion to zero.

12. Sliding friction is caused by the attraction between the two surfaces.

13. If an object accelerates, a push or pull must be acting on it.

14. If an object is not moving, the net force working on it is zero.

15. Friction can be reduced but never eliminated.

16. The word in the puzzle is __________________________________________.

15 2 11 3 6 11 15 7 10 13 11 14 4 5 15 6 2 7 11 10 15 13 13 3 7 11 2 8 5

14 1 12 5 7 12 1 9 2 1 3 12 9 15 2 11 8 13 2 5 8 3 14 12 14 6 3 8 5

13 3 4 8 10 9 4 11 3 4 2 12 8 6 12 12 9 7 9 15 2 11 10 11 6 3 15 9 4

10 8 2 3 13 2 5 8 12 10 8 9 9 10 11 3 8 6 12 4 9 9 13 12 4 8 11 4 1

15 9 11 9 14 8 6 4 13 5 3 11 2 14 3 8 12 7 3 10 1 14 7 2 1 12 9 2 10


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Newton’s Second Law

Directions: Select the term from the following list that matches each description. Some terms will not be used.a. 16 N e. a = F

m i. 600 Nb. –16 N f. normal forces j. Newton’s second law of motionc. gravity g. air resistance k. terminal velocityd. F = ma h. F = m(9.8 m

s2 ) l. Newton’s first law of motion

1. acts against the direction of motion and gets larger as an object moves faster

2. Force is equal to mass times acceleration.

3. An object acted upon by a net force will accelerate in the direction of that force.

4. the gravitational force on any object near Earth’s surface

5. the outward forces exerted by a surface

6. the speed an object reaches when the force of gravity is balanced by the force of airresistance

7. What force must be applied to a 60-kg object to make it accelerate at 10 m/s2?

Directions: Study the illustration of the diver. Then identify each statement as true or false. If the statement isfalse, change the word(s) in italics to make it true.

Reinforcement22


8. After the diver jumps forward from the diving board, the force ofgravity will accelerate the diver parallel to the direction of motion.

9. When the diver hits the water, the force of the water against herbody can stop it about five times faster than the pull of gravity thataccelerated it.

10. If the diver doesn’t have the correct form when she enters the water,the force of the water can accelerate her speed.

11. Air resistance prevents the diver from moving in a straight line onceshe jumps from the platform.

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Directions: Complete the table by naming the action and reaction forces in the following examples.

Newton’s Third Law

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Directions: Complete the following sentences using the correct terms or phrases.6. Newton’s third law states, “For every action, there is an equal but ____________________.”

7. There is no ____________________ in time between the action and the reaction.

8. One reason it’s often easy to miss an action-reaction pair is because of the ____________________of one of the objects.

9. Action-reaction forces are always the same ____________________ but are in

opposite ____________________.

10. When you swim in water, your arms push the water ____________________. The water

reacts by pushing ____________________ on your arms, causing your body to

accelerate ____________________.

Directions: Answer the following question using complete sentences.

11. How could the action force of a canoe moving through water be increased?

Example Action force Reaction force

1. A flying bird

2. Two bumper carscollide

3. Holding your handout the windowof a moving car

4. Walking

5. Touching yourfinger to your nose


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Gyroscopes

A gyroscope is a kind of top that spinsaround a central axis. If you’ve ever seen a toygyroscope, you know it’s a spinning wheel thatcan balance on a string or a fingertip. Even ifyou tilt your finger out to the side, the gyro-scope continues to spin. That’s because ofNewton’s first law—an object continues itsstate of motion unless a force acts upon it.Even though you are moving your finger, noforce is applied to the gyroscope so it contin-ues its spin. In keeping with Newton’s first law,a gyroscope always points in just one direction.That’s why it looks as if it’s defying gravity.

Navigation by GyroscopeBut gyroscopes aren’t just toys; they’re used

in everything from boats to missile guidancesystems to the Hubble Space Telescope. Gyro-scopes can be mounted on boats, airplanes,telescopes, or other platforms so that whenthe object moves, the gyroscope (which continually points in the same direction)detects changes in altitude. Altitude in thiscase is defined as “the position of an aircraft orspacecraft determined by the relationshipbetween its axes and the horizon or other reference point.”

In other words, a gyroscope can tell whensomething is going off course.

The Hubble Telescope uses six gyroscopes.Three are used to keep the telescope pointing inthe right direction; the other three are spares.The Hubble gyroscopes are the most accurate inthe world. An airplane usually uses three gyro-scopes to help in navigation. Each one spins in adifferent direction. When the plane changesdirection, one of the gyroscopes detects it. Themovement is measured by a magnetic sensor,and the airplane’s navigator or pilot calculates anew path for the airplane to follow.

Other GyroscopesGyroscopic function is also used in race

cars and motorbikes. In race cars, for example,the engine acts as a gyroscope. Mechanicsrotate the engine in one direction so that asthe car goes around the track, the enginepushes the front of the car’s body down andthe back of the car’s body up. This helps thecar stay on the track. It’s truly amazing howpowerful gyroscopic effects can be.

Directions: Use textbooks, the library, or other resources to help you answer the following questions.1. Restate Newton’s first law of motion in your own words.

2. How important do you think the three gyroscopes are to the Hubble Space Telescope? Explain.

3. Do gyroscopes defy gravity? Explain.

4. Name another well-known space project that uses gyroscopes to operate.

Enrichment11


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Off to the Races

1. If your go-cart weighs 500 kg, what is the force you will have to apply to accelerate it at +1.5m/s2?

2. You discover that Eunice and Bert’s go-cart weighs 400 kg and will have a 675 N force acting onit. How fast will it accelerate (to the nearest tenth)?

3. If you are able to decrease the mass of your go-cart by 15 percent, and the same force that wasapplied in number 1 is applied, will your go-cart be able to beat Eunice and Bert’s? (Roundyour answer to the nearest tenth.) Explain.

It’s Friday afternoon and all you can thinkabout during science is the upcoming go-cartrace. You and a friend have been working onyour entry for over two months. With raceweekend only a month away, there is still a lotof work to be done.

Your friend comes over after school with a wor-ried look on her face. She explains to you thatEunice and Bert have designed an awesome cartthat no one could possibly beat. As the two of yousit and mope, an idea springs into your head.

“Wasn’t the science teacher talking aboutsomething that had to do with acceleration?Yeah, it was something about Newton.”

Finally, you remember exactly what it was.“Newton’s second law of motion states thatthe acceleration of an object is directly proportional to the force acting on it, andinversely proportional to its mass.”

You look to your friend with a smile onyour face and tell her it is time to get to work.You explain that by using Newton’s second lawof motion you can help make sure that yourgo-cart is the fastest one at the races.

Newton’s second law of motion can be

written as acceleration = net forcemass or a =

fnet.

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Jupiter Furniture Design

Your mother works for NASA and has toldyou that we are very close to colonizingJupiter. She tells you this is top secret and thatyou shouldn’t tell anyone else. You always havebeen an entrepreneur and immediately beginthinking about ways you could profit from thenewly divulged information.

As you sit at your desk and stare aroundyour bedroom, you realize that furniture willbe needed if people are going to colonizeJupiter. As quickly as your excitement builds,however, it disappears. You are certain thatthere are enough furniture designers in theworld already.

Your father comes home and calls you tocome down for dinner. As your dad sits in hischair, it collapses to the floor. Everyone in thefamily begins to laugh, including your father.

He continues to laugh and jokes about need-ing to lose weight as he gets another chair. Allof a sudden it hits you—your dad’s mass andthe gravity acting on it caused the chair to collapse.

After dinner you dig out your science bookand get to work. You go directly to the sectionon Newton’s laws of motion and refresh yourmemory. It appears that Newton’s third lawwill help you. It states that, “an action forcehas an equal, but opposite, reaction force.”

On Earth, gravity is measured at 9.8m/s2

down. That means that when your dad sits ina chair, he is applying a force equal to his massmultiplied by the force of gravity. This can bewritten as Force = Mass ✕ Gravity, or mg.When you calculate the weight of an object,you write your answer in newtons (N).

1. Your father used to weigh 484 N. What was his mass (to the nearest tenth)?

2. Your father gained 30 N, which caused his chair to break. What was his new mass? How muchforce was acting on the chair? How much force was reacting?

3. How much force will your father exert on Jupiter? (Jupiter’s gravity is 24.5m/s2.)

4. What will be the reaction force necessary to hold your father up and keep his chair from collapsing on Jupiter?

5. Explain what these problems have to do with Newton’s third law.

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Section 1 Newton’s First Law

A. ______________—push or pull on an object

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

2. When forces are _________________ forces, they cancel each other out and do not change an

object’s motion; when forces are ___________________ forces, the motion of an object changes.

B. Newton’s __________________ of motion—an object will remain at rest or move with

constant speed unless a net force is applied.

C. _________________ is a force that resists sliding between two touching surfaces or through

air or water.

1. Friction ___________________ an object’s motion.

2. _______________ friction—the type of friction that prevents an object from moving when

a force is applied

3. ________________ friction is due to the microscopic roughness of two surfaces; it slows

down a sliding object.

4. ________________ friction between the ground and a wheel allows the wheel to roll.

Section 2 Newton’s Second Law

A. Newton’s ___________________ of motion connects force, acceleration, and mass; it explains

that an object acted upon by a force will accelerate in the direction of the force; acceleration

equals net force divided by mass.

B. ________________—attractive force between two objects; depends on the mass of the objects

and distance between them; gravitational force is also called _______________.

C. The second law explains how to __________________ the acceleration of an object if its mass

and the forces acting on it are both known.

D. In circular motion, the ____________________ force is always perpendicular to the motion.

E. The __________________________ is reached when the force of gravity is balanced by air

resistance; the size of the air resistance force depends on the shape of an object and its speed.

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F. An object can speed up, slow down, or turn in the direction of the net force

when __________________ forces act on it.

Section 3 Newton’s Third Law

A. Newton’s __________________ of motion states that forces always act in equal but opposite

pairs; for every action there is an equal and opposite reaction.

B. Action-reaction forces are always the same size but are in _________________ directions and

act on different objects.

1. When the mass of one object is considerably _______________ than the mass of another

object, the action-reaction force is not noticeable.

2. ____________ and ______________ exert action-reaction forces with objects such as

hands or canoe paddles.

3. A _______________ launches due to the equal but opposite forces of the burning fuel.


Note-taking Worksheet (continued)


Assessment

Assessment

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Chapter Review


Part A. Vocabulary ReviewDirections: Match the terms in Column II with the descriptions in Column I. Write the letter of the correct termin the blank at the left.

Column I

1. An object at rest or moving at a constant speed in a straight path will continue to do so until a net force acts on it.

2. An object acted upon by a net force will accelerate in the direction of the force according to the equation

acceleration = net forcemass .

3. the outward force from a surface

4. a push or a pull

5. The net forces on an object are not zero.

6. the total force felt by an object

7. Forces always act in equal but opposite pairs.

8. two or more forces whose effects cancel each other

9. the rubbing force that acts against motion between two touching surfaces

Column II

a. Newton’s first lawof motion

b. unbalanced forces

c. balanced forces

d. friction

e. net force

f. normal force

g. Newton’s third lawof motion

h. force

i. Newton’s secondlaw of motion

Directions: Complete the following sentences using the terms listed below. Some terms may not be used.

accelerate friction velocity static

sliding slipping wheel strength

brake inertia terminal velocity

10. An object will ____________________ when the net force is not zero.

11. ____________________ will never speed up an object.

12. The friction that prevents an object from moving when a force is applied is

____________________ friction.

13. The friction that slows down an object that slides is ____________________ friction.

14. A(n) ____________________ helps reduce sliding friction.

15. Normal force is supplied by the ____________________ of the surface.

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Chapter Review (continued)


16. The speed an object reaches when the force of gravity is balanced by the force of air resistance

is called ____________________.

17. Earth has so much ____________________ that it hardly accelerates when you push againstthe ground while walking.

Part B. Concept ReviewDirections: Correctly complete each sentence by underlining the best of the three choices in parentheses.

1. (Static, Sliding, Rolling) friction keeps an object at rest.

2. A force can (push, pull, either push or pull).

3. The unbalanced force that stops almost everything is (gravity, friction, momentum).

4. An object will accelerate in the direction of the (net force, balanced forces, normal force).

5. A net force acting on an object changes the object’s (mass, size, motion).

6. Newton’s (third, second, first) law of motion describes the connection between an object

supplying force and the object receiving the force.

7. A force in the opposite direction to the motion of the object will cause the object to

(speed up, slow down, turn).

8. If an object is at rest, all forces acting on that object must be (unbalanced, balanced, normal).

Directions: Answer the following questions using complete sentences.

9. Explain why it is easy to miss an action-reaction pair. Give an example.

10. Why does friction never speed up an object?

Assessment

Transparency Activities


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Section FocusTransparency Activity11


Little things happen every day that we don’t really think about. If acup of coffee gets knocked off a table, we grab a towel or a mop toclean up the mess. But what if we looked at the event closely? There’s a lot to be learned from even the most common occurrences.

Another Cup, Please

1. What causes the cup to break when it strikes the floor?

2. Why do the pieces eventually stop moving?

3. What determines how far and in what direction the coffee cup(and coffee) will travel?

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Have you ever gone upside down on a roller coaster? What kept thecar on the track? In the cartoon, Calvin is pulling the sled far up thehill so he can get a good start.

Loop D’loop

1. Does it make a difference where Calvin begins his descent?Explain.

2. How does friction figure into Calvin’s scheme?

3. How will gravity affect Calvin if he makes it into the loop?

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

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People run for many reasons. Sometimes it’s for exercise or competition, and sometimes it’s for the pure joy of running. What-ever the reason, running is about applied forces.

Pushing the Limits

1. When you run, in which direction does your body exert force?

2. How does friction help a runner?

3. How will this athlete stop at the end of the sprint?

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Teaching TransparencyActivity11 Newton’s Laws of Motion


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Teaching Transparency Activity (continued)

1. What is force?

2. What is a balanced force?

3. In the top picture on the transparency, what is the club doing to the ball?

4. Describe Newton’s law of motion that explains the dynamics behind the rocket engine (middleimage on the transparency).

5. The girl pushing the sled is illustrating which of Newton’s laws of motion?

6. What unbalanced force brings nearly everything to a stop?


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AssessmentTransparency Activity

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


1. All of these objects have unbalanced forces acting upon themEXCEPT ___.A AB BC CD D

2. Rolling friction pushes on an object that is rolling. According tothis definition, which of these examples shows rolling friction?F A and DG B and AH C and BJ D and C

3. A force is a push or pull. Which force is acting on all of the objectsin the diagram?A Static frictionB MagnetismC GravityD Acceleration

A B C D

force and newton’s laws -...

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