Collisions Between Objects

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LESSON 4 | ENGINEER IT Collisions between Objects

Percussionists use collisions to make music.

By the end of this lesson . . . b.v./Alamy TSIKAS/epa european pressphoto agency ©MICK © Houghton Mifflin Harcourt • Image Credits: you will be able to apply Newton’s laws of motion to design a solution to a problem involving two colliding objects.

68 Unit 1 Forces and Motion DO NOT EDIT--Changes must be made through "File info" LONumber=6P1_0570; CorrectionKey=NL-A

Go online to to view view the the digital digital version version of of the Hands-On Lab for this lesson and to download additional lab resources.

CAN YOU EXPLAIN IT?

HowHow can can Newton’s Newton’s laws 3rd lawbe applied be applied to protect to protect a smartphone a device's screen screen during during a a collision? collision?

People carry smartphones everywhere. If people are not careful, they can drop or bump their smartphones into other objects. Smartphones may be damaged in a collision.

1. Oh no! Have you ever seen this problem with a smartphone or a tablet? Write a step-by-step account of what you think might have happened to cause damage to the smartphone pictured. © Houghton Mifflin Harcourt • Image Credits: ©Patrick Strattner/Getty ©Patrick Images © Houghton Mifflin Harcourt • Image Credits:

EVIDENCE NOTEBOOK As you work through the lesson, record evidence that helps you determine how to protect a smartphone screen during a collision.

Lesson 4 Engineer It: Collisions between Objects 69 LONumber=6P1_0570; CorrectionKey=NL-B DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 70 the meteoroid isdestroyed. the meteoroid. However, theeffects are verydifferent. Earth’s crustgetsasmalldent, but force thatthemeteoroid exertsonEarthisthesame strength astheforce Earthexertson bat, theballfliesawaybutyou andthebatdonot.Whenameteoroid strikes Earth,the smaller objectisgreater thanthe effect onthelarger one.Whenyouhittheballwith during thecollisionitself, whichisoften averyshortperiodoftime. sometimes calledactionforce and reaction force orforce. Theseforces pairs actonly second objectexertsanequalbutoppositeforce onthefirstobject.Theseforces are on thebat.Thatiswhyyoufeelastingingsensationin your hand asthebatvibrates. with abat.Thebatcollidestheballandpushesit away. Theballalsoexertsaforce When twoobjectscollide,eachobjectpushestheother. Thinkabouthitting asoftball Newton’s Third Law of Motion and Collisions 2. laws ofmotion. object inacollisioncanbedescribedbyNewton’s analyze thansimplecollisions.Themotionofeach These complexcollisionsmaybemore difficult to may involvemanyobjectsandmultiplecollisions. the ground. Othercollisions,suchascarcrashes, A collisionmaybeassimpleaballbouncingon Collisions betweenobjectshappeneveryday. Unit 1Forces and Motion after theimpact? What doyouthinkhappenedtolifeinthearea crater’s shapegiveyouaboutthecollision? of MeteorCrater. Whatinformationdoesthe changed duetoweathering.Look attheshape occurred longago,andthecraters havebeen collided withEarth.Manyofthesecollisions Discuss When themasses oftwocollidingobjectsare verydifferent, theeffect onthe Newton’s third lawstatesthatwhenoneobjectexertsaforce onanother, the Over theyears,manymeteoroids have Applying Newton’s Laws Collisions to EXPLORATION 1 deep. Itwasformedapproximately 50,000yearsago. sites onEarth.Thecrater isalmost1mileacross and240feet Meteor Crater inArizonaisoneofthebestpreserved impact

Newton’s Second Law of Motion and Collisions The robots are kicking identical balls; each kick is a collision. The effect of each kick on each ball depends on the ball’s initial motion and the force of the kick. The force of the robot’s kick causes the ball to accelerate. Remember that a change in the speed or direction of an object is acceleration. The robot is much more massive than the ball, so it accelerates less than the ball during the collision. This example illustrates Newton’s second law of motion—the acceleration of an object depends on the mass of the object and the force applied to it (F = ma).

Robots Collide with Identical Balls

An object accelerates in the direction of the net force applied to it. The greater the force applied to the object, the greater the acceleration.

3. If the balls start at rest, the ball kicked with the most force will be moving faster / slower than the other balls after it is kicked. The ball with the greatest velocity will travel the farthest/ least after it is kicked. The yellow/red/blue robot kicked with the most force. The evidence is the distance the ball traveled/size of the robot. 4. Draw A satellite collides with debris in space. Draw a picture showing the collision. Show the forces and indicate their likely effects. © Houghton Mifflin Harcourt

Lesson 4 Engineer It: Collisions between Objects 71 LONumber=6P1_0570; CorrectionKey=NL-B DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 72 applied toeach situation. about thefollowingexamples, considerhoweachofNewton’s lawsof motioncanbe a collisionaffect theobjects’motionsbefore, during,andafter acollision.Asyouthink Let’s lookatsomeexamples ofsimplecollisionstoseehowthe masses oftheobjectsin can helpengineersandscientists explainmore complexcollisions, suchasacarcrash. collision canbeanalyzedusing Newton’s lawsofmotion.Analyzingsimplecollisions In asimplecollision,deformationsandenergy losses are notconsidered. Asimple Simple Collisions 5. a collision.Howdoesinertiaexplainthecrumplingofcarduring thecollision? continue tomovedueinertia.Thisiswhywehaveseatbeltsstoppassengers during know thatwhenthecarstops,passengers will affect collisions?Look atthecarcrash shown.You resistance toachangeinmotion.Howdoesinertia describes theinertiaofanobject,orobject’s vehicle rather thanaffecting thepassengers. energy from themovingcargoesintodeforming acting onthepassengers inthecar. Someofthe important safetyfeature becauseitreduces theforce deform inspecificwaysduringacollision.Thisisan shape, duringacollision.Carsare designedto collisions. Manyobjectsactuallydeform,orchange Different objectsbehavedifferently during Collisionsand Newton’s First Law of Motion Unit 1Forces and Motion car throughout thecollision. knowledge ofNewton’s lawsofmotionandcollisionstodescribethe Withapartner, analyzethecollisionshowninphoto.Useyour Collaborate Recall thatNewton’s firstlawofmotion from harmincollisionssuchasthisone. Automotive engineersstudycollisionstoprotect passengers

© Houghton Mifflin Harcourt Explainhowthecollisionwouldornotchangeifboth marbleswere moving 6. speed thebluemarbleinitiallyhad. marble stopsmovingandtheorange marblebeginsmovingtotherightatsame marble’s speedwilldecrease. Onepossible result ofthiscollisionwouldbethattheblue the oppositedirection ofthemarble’s originalvelocity. Sotheblue exerted onthebluemarble.Inthisexample,acceleration isin opposite. Thebluemarbleaccelerates inthedirection oftheforce acceleration oftheballsduringcollisionwillalsobeequal and the masses are thesame,Newton’s secondlawtellsusthatthe on theotherisequalinstrength andoppositeindirection. Because marbles collide,Newton’s third lawtellsusthattheforce eachexerts orange marblewillstayatrest—until theycollide,thatis.Whenthe law, weknowthatthebluemarblewillcontinuetomove,and from left toright.Theorange marbleisatrest. From Newton’s first the samemass. Before thecollision,bluemarbleismoving Consider thetwomarblesshowninimage.Both have Collisions with between Objects Equal Masses Whichofthestatements are trueaboutthecollisionoftwoobjectswithdifferent 7. collision betweentwoobjectswithdifferent masses? the appliedforce. Howwillthatrelationship affect a acceleration ofanobjectdependsonitsmass and From Newton’s secondlaw, weknowthatthe shown willexperienceanequalandoppositeforce. masses. We knowthateachballinthecollision Many collisionsinvolveobjectswithdifferent Masses Different with Objects between Collisions motion tosupportyourreasoning. before thecollision,insteadofonlybluemarblemoving. UseNewton’s lawsof D. Eachobjectwillaccelerate inanoppositedirection from theotherbutata C. Themore massive objectwill exertagreater force ontheless massive object. B. Eachobjectexperiencesanequalandoppositeforce. A. masses basedonNewton’s lawsofmotion? Theless massive objectwillaccelerate duetotheforce ofthecollision,but more massive objectwillnot. different rate. dimensions, butthesteelballhasagreater mass. A glass marble collideswithasteelball.Bothhavethesame Lesson 4Engineer It:Collisions betweenObjects shown intheimage. force ontheothermarble.Thisforce pairis During thecollision,eachmarbleexertsa 73 LONumber=6P1_0570; CorrectionKey=NL-A DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 74 direction ofeachthesequantities. positive andnegativesignstoindicatethe have bothmagnitudeanddirection. We use Recall thatforce, velocity, andacceleration the sameamountbutinoppositedirections. Newton’s lawstellusthattheywillaccelerate When twoobjectswiththesamemass collide, directions. Bothmarbleshavethesamemass. are movingatequalspeedsinopposite Before thecollision,thetwomarblesshown 9. 8. 12. 11. Thevelocitiesofthemarbleschange,soweknowthataccelerate . 10. Unit 1Forces and Motion V During thecollision,bothmarblesaccelerate toastop,or0m/s. Usetheformula direction. Whatisthevelocityoforange marblebefore thecollision? of 2m/s. Theorange marbleismovingatanequalspeedbutintheopposite Before thecollision,bluemarbleismovingfrom left toright,andithasavelocity Blue marble:0m/s –2m/s = Orange marble:0m/s –(–2m/s) =2m/s Use Newton during thiscollision. the accelerations oftheblueandorange marblesduring thiscollision? collision, whichisthesameforbothobjectsincollision. What canyousayabout by time.To calculateacceleration duringacollision,thetimeisduration ofthe Acceleration istherate ofchangevelocity, whichisthechangeinvelocitydivided What canyousayaboutthechangeinvelocitiesofmarbles? final –V Analyze Acceleration aCollision During the MathDo initial to calculatethechangeinvelocitiesfororange andbluemarbles. ’ s lawsofmotiontowriteadescriptionthebothmarbles and oppositeindirection. Notice thattheforce arrows oneachmarbleare equalinmagnitude

© Houghton Mifflin Harcourt • Image Credits: ©Freedom_Studio/Shutterstock each collisionasevidenceoftheselosses. thermal energy into othertypesofenergy suchassoundenergyand there are somelosses astheenergy istransformed other ballsduringeachcollision.Duringtransfer have kineticenergy. Thisenergy istransferred tothe object willnotmove.Whentheballsare moving,they then moveasaresult ofthecollision,butsecond of thecollisiontothird object.Thethird objectwill The objectinthemiddleeffectively transfers theforce identical objectthatistouchingathird identicalobject? What happenswhenanobjectcollideswithasecond in Contact Collisions with Objects Theblueteamisrolling oneoftheirballstoward 15. after eachteamthrows theirballs. have theballthatisclosesttotarget ball toward atarget ball.Thegoalofthegameisto In thegameofbocce,twoteamsroll theirballs Shot Bocce a Analyze with evidence. Make anargument aboutwhetherthisistrueornot.Supportyourclaim that oncetheNewton 13. good shotfortheblueteam? will happenwhentheballscollide?Willthisbea opponent’s ballasshown.Whatdoyoupredict another oftheirballs,whichistouchingan Whymightasmartphonebedamagedwhenitfallsonhard surface? 14. EVIDENCE NOTEBOOK Language SmArtsBasedonNewton’s lawsofmotion,youmightexpect Record yourevidence. . You canhearaclickingsoundduring ’ s cradle issetinmotion,itwillstaymotionforever. , Lesson 4Engineer It:Collisions betweenObjects when objectsare incontact. The Newton’s cradle isanexampleofhowcollisionswork 75 LONumber=6P1_0570; CorrectionKey=NL-A DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 76 18. 17. develop solutionstoreduce thedamagecausedbycollisions. nail. Ouch!Becausedamagingcollisionswillhappensometimes, engineersworkto can bedangerous ordamaging. Imaginethehammerhitting yourthumbinsteadofthe such ashammeringanail.Unfortunately, notalleffects ofcollisionsare desirable; they The bird usesacollisiontoitsadvantage.Humansalsousecollisionsachievegoal, Thebird fliesoverdifferent surfaces.Howwill 16. surface orahard surface. ball isnotmoving.Atennisbouncesdifferently onaclaysurfacecompared toagrass lower force. Ifaballismovingtoward aplayer, akickwillhavedifferent effect thanifthe greater acceleration whenitiskicked withagreater force thanwhenitiskicked witha involved andthemotionofobjectsjustbefore thecollision.Asoccerballhasa You knowfrom experiencethatcollisionshavedifferent effects dependingontheobjects of CollisionsEffects Unit 1Forces and Motion forces actingonthestunt personduringthecollision. With apartner, discuss howthemotion ofthestuntpersonrelates tothe Discuss middle, andendofthecollisionwithairbag. a seriesofthree imagesshowingthemotionofstuntpersonatbeginning, slowly bringthestuntpersontoarest. Imaginethiscollisioninslowmotion.Draw Draw affect whethertheclamwillopen? the surfaceontowhichbird drops theclam Engineering aSolution aCollision to Problem Imagineastuntpersonfalling ontoanairbag.Theairbagisdesignedto EXPLORATION 2 A bird drops aclamtobreak theshellopenforfood.

Hands-On Lab Test Packing Materials

Packaging designers need data on packing materials in order to MATERIALS choose the best materials to meet their needs. Test engineers design tests to collect this data. In this lab, you will design a testing method • box, cardboard, about 6 in. on each side and perform tests on different packing materials. A successful testing • bubble packing method is repeatable and will give engineers the data they need to • cotton balls choose the best materials for their packing needs. • egg, hard-boiled • meterstick Procedure and Analysis • rubber bands • scale STEP 1 The list below is an incomplete list of criteria and constraints for this engineering design problem. With your group, • tape or glue discuss the engineering problem and add at least one constraint and one criterion to better define the problem.

Criteria Constraints Testing method can be used to test a Testing method can be performed with variety of materials. materials available in the classroom

Testing can be completed within one class period.

STEP 2 Brainstorm ideas for testing methods that can be used to evaluate the effectiveness of different packing materials. Do not evaluate the ideas yet. Record each idea in a notebook.

STEP 3 Choose a method from Step 2 that you will implement. Draw or describe the method, and explain why it is the most promising solution. Show your method and explanation to your teacher. © Houghton Mifflin Harcourt

Lesson 4 Engineer It: Collisions between Objects 77 LONumber=6P1_0570; CorrectionKey=NL-B DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 78 STEP 6 STEP 5 STEP 4 Unit 1Forces and Motion item duringacollision? Based onyourtesting,whatqualitiesmake amaterialusefulforprotecting an you mightimprove yourtesting method. Does yourtestingmethodsatisfycriteriaandconstraints? Describehow packing materialsbeingtested. and record thetestresults foreachofthe Implement yourchosentestingmethod, Students examinetheireggafter atest.

© Houghton Mifflin Harcourt • Image Credits: ©Viktor Cap/Alamy is transformed intosoundenergy andislostfrom thesystem.WhileNewton on thesituation.For example,whenapercussionist hits adrum,someoftheenergy another form,someoftheenergy islost.Theselosses maybedesirable depending energy transforms backintokineticenergy. Wheneverenergy istransformed into the objectdeforms.Whenreturns toitsoriginalshape,thiselasticpotential elastic material,theenergy maytemporarily bestored aselasticpotentialenergy as forms suchassoundenergy orthermalenergy. Ifanobjectinacollisionismadeof object totheotherduringcollision.Someofenergy istransformed intoother Some oftheenergy remains withtheobject.Someofenergy istransferred from one object ismoving,ithaskineticenergy. Whathappenstothisenergy duringacollision? Objects andsystemsmaycontaindifferent amountsandtypesofenergy. Whenan Collisions and Energy other conceptsare neededtofullyanalyzeacollision. motion canbeusedtodescribetheofobjectsduringacollision,sometimes 19. Language from thetexttosupportyourreasoning. Use Newton’s lawsofmotionandinformation Explain indetailwhythetennisballbounces. tennis ballduringacollisionwiththeground. Howcanthelabresults helpyoudesignprotection forasmartphone 20. EVIDENCE NOTEBOOK screen during acollision?Record yourevidence. SmArts The imageshowsa A tennisballdeformsasitbouncesontheground. Lesson 4Engineer It:Collisions betweenObjects Explore ONLINE! ’ s lawsof 79 LONumber=6P1_0570; CorrectionKey=NL-A DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 80 Explainhowyouwould begindesigninga 23. must beprotected. minimize wasteandpackageweight,buttheproduct and companiesdesire minimalpackagingto collisions thatoccurduringshipping.Consumers what isbeingshippedneedstobeprotected from Packages are shippedallovertheworld.Often Packaging Design Unit 1Forces and Motion item, suchasalaptop,duringshipping. solution totheproblem ofprotecting afragile 21. Objects AandB,eachwithamass of20kg, collidewithamuchlarger object. 22. Use theaccelerations ofobjectsAandBtoexplainhowacollision’s duration changing theduration ofacollisionaffects themagnitudeofacceleration. a collision,theduration ofthecollisionisextended.Domathtoseehow have stoppedaccelerating relative toeachother. Ifanobjectdeformsduring initial contacttothetimewhenobjectsare nolongerincontactorwhenthey When objectscollide,theduration ofthecollisionismeasured from thetimeof Do theMath of eachobjectusingtheformulaa=(V The duration ofthecollisionobjectBis0.002s.Calculateacceleration full stopafter thecollision.Theduration ofthecollisionobjectAis0.001s. Both AandBhaveavelocityof10m/sjustbefore thecollisionandcometoa affects theobject’s acceleration. Object B Object A | AnalyzetheEffect ofCollisionDuration onAcceleration 0 m/s–10 0 m/s–10 0.001 s s final = = –V initial A drone deliversapackage. –10 m/s –10 m/s 0.001 s )/t. s = = –10,000 m/s 2 m/s 2

TAKE IT FURTHER

Continue Your Exploration

Name: Date:

Check out the path below or go online to choose one of the other paths shown.

Go online to Careers in • Wrecking Ball Demolitions choose one Engineering • Propose Your Own Path of these other paths.

Crash Test Engineer You have probably seen videos of crash test dummies in a car collision. Crash test engineers design ways to test the effects of a car collision on a car’s passengers and to improve car designs to be safer. Recording devices on crash test dummies measure forces experienced by the bodies during a collision. Engineers then analyze this data and use it to design better safety devices for vehicles. Safety measures include devices such as safety belts and airbags, which apply forces directly to passengers to protect them. Car bodies themselves are engineered to deform in specific places to protect the passengers. A crash test engineer often has a degree in mechanical engineering or industrial engineering. The job requires an understanding of physics, math, and how to use computers to analyze data. © Houghton Mifflin Harcourt • Image Credits: ©fStop Images - Caspar Benson/Brand X © Houghton Mifflin Harcourt • Image Credits: Pictures/Getty Images

A crash test is performed with a cyclist colliding with the side of a car. Video and sensors on the crash test dummies record data about the acceleration and forces experienced by the crash test dummies.

Lesson 4 Engineer It: Collisions between Objects 81 DO NOT EDIT--Changes must be made through “File info” LONumber=6P1_0570; CorrectionKey=NL-B

TAKE IT FURTHER

Continue Your Exploration

1. Based on the description of a crash test engineer’s job, which of these engineering tasks would the engineer work on? Choose all that apply. A. testing prototypes of a new design to determine whether they meet safety criteria B. choosing materials used in automobile manufacturing C. studying customer preferences to improve marketing D. using a computer to analyze large amounts of data

2. Which of the following may affect a passenger’s safety during a collision? A. the mass of the automobile in which the passenger rides B. the mass of the automobile that collides with the passenger’s vehicle C. the velocity of the passenger’s vehicle D. the acceleration of the passenger’s vehicle during the collision

3. Automobiles did not always have safety devices such as safety belts, airbags, and roll cages. What societal needs led to the creation of these safety measures and the career of crash test engineering?

4. Collaborate Work with a partner or a group. Consider the engineering design process involved in making cars and trucks. Make a list of other jobs in the automotive industry that could also be filled by mechanical or industrial engineers.

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LESSON 4 SELF CHECK

Can You Explain It?

Name: Date:

How can Newton’s laws be applied to protect a smartphone screen during a collision?

EVIDENCE NOTEBOOK Refer to the notes in your Evidence Notebook to help you construct an explanation for how to protect a smartphone screen during a collision.

1. State your claim. Make sure your claim fully explains how a smartphone can be protected during a collision. ©Patrick Strattner/Getty©Patrick Images

2. Summarize the evidence you have gathered to support your claim. © Houghton Mifflin Harcourt • Image Credits: © Houghton Mifflin Harcourt • Image Credits:

Lesson 4 Engineer It: Collisions between Objects 83 LONumber=6P1_0570; CorrectionKey=NL-B DO NOT EDIT--Changes mustbemadethrough “Fileinfo” 84 Thephotoshowsevidenceofmeteorscollidingwith 5. Use the photo to answer 5. Question Whichofthefollowingcriteriaare satisfiedbythemat 4. Thematinthephotohelpsprotect thegymnastby 3. Use the photo to answer 3and 4. Questions lesson. of your the following to check the understanding questions Answer In asimplecollisionbetweentwoobjects,Newton’s 6. Unit 1Forces and Motion the collisionbetweengymnastandfloor. D. Thecollisionswere sosmallthatnoforces acted C. Themoon andmeteorsexertedequalbutopposite B. Duringeachcollision,themoonexertedagreater A. said aboutthesecollisions? the moon.According toNewton’s laws,what canbe D. protects agymnastfrom injuryduringadismount C. is easilytransported byasingleperson B. doesnotinterfere withgymnastduringaroutine A. in thephoto? of thegymnastduringcollision. Decreasing /Increasing decreasing /increasing collision decreases the Neither object C. Onlyobjectsthatare movingbefore thecollision B. Bothobjects A. which oftheobjects? laws ofmotioncanbeused todescribethemotionof Becausethemoonhasnoatmosphere, Newton’s fitsinasmallcar the moonandmeteors. laws cannotbeappliedtothecollisionsbetween collisions. on eitherthemoonormeteorsduring forces ontheeachother. on themoon. force oneachmeteorthanexerted from therings on therings acceleration /velocity theduration of theduration ofthe LESSON 4 SELF CHECK 4 LESSON Checkpoints

© Houghton Mifflin Harcourt • Image Credits: (t) ©Freedom_Studio/Shutterstock; (b) ©Mira/Alamy problem, includingaproblem ofobjectscolliding. The engineeringdesignprocess canbeusedtodevelopasolutionanengineering in acollision. Newton’s lawsofmotioncanbeusedtodescribethemotions ofobjectsinvolved Complete thissectiontoreview themainconceptsoflesson. Interactive Review LESSON 4 SELF CHECK 4 LESSON Collisionsmaycauseunwanteddamage toan B. HowcanNewton’s lawsofmotionbeusedto A. Lesson 4Engineer It:Collisions betweenObjects protect anobjectduringacollision. process canbeusedtodesignasolution object. Describehowtheengineeringdesign analyze thecollisionbetweentwoobjects? 85