Science24Notes Module4

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Science24

Module4

Chapter13–ANeedforSafety–page232AnalyzingtheDanger

• Almostallvehiclecollisionsarepreventable

o SeeTable1‐PercentageofDriverInjuries&Fatalities‐page234o SeeTable2‐CanadianCausesofDeath‐page235

• InjuriesinMotorVehicles

o Cuts,bruises,&brokenboneso Whiplasho Seriousburnso Internalinjurieso Head&spinalinjuriesthatmayleadtoblindness,

paralysis,orbraindamageReactionTime

• ReactionTime‐thetimeittakesyoutorecognizeaproblem&actonit

• ReactionTime&Distractionso Distraction

Anythingthattakesyourattentionawayfromwhatyouaresupposedtobedoing

Maybeinsideoroutsidethecar Examples‐

•

•

•

• Fatigue&ReactionTimeo 15%ofdriversadmittheyhavefallen

asleepwhiledrivingo Noamountofcaffeine,loadmusic,cold

air,orpinchingyourselfwillkeepyouawake

o Pullover&takeanap!

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• ReactionTime&Drugso Impaired‐youareunabletofunctionnormallyo Alcohol,prescriptiondrugs,&non‐prescriptiondrugscanaffectthe

humanbodyinwaysthatmakeitdangerousforausertodrive Alcohol

• Isadepressant• Itslowsreactions,lowerco‐ordination,&makesthe

driversleepyoncethealcoholreachesthebrain

• BloodAlcoholConcentrationo BACo Thenumberofmgofalcoholinamlofbloodo IfBAC=0.08,thismeansthereare0.08mgofalcoholineachmlof

thatperson’sbloodo Dependsonthenumberofdrinksconsumed&bodyweight

Canvaryifpersonistiredorhungry 2drinkswillputa45kgpersonoverthelegallimit

o Onedrink 45mlofhardliquor(40%) 150mlofwine(11%) 350mlofbeer(4%)

• BloodAlcohol&theLaw

o LegallimitinCanada=0.08o Policeofficerscanchargeanydriverwith

alcoholontheirbreathwhenpulledovero Thebodygetsridof0.015BACunitsperhour

CollisionInjuries

• Traumao Thephysical&emotionalstressthatresultsfromanaccidento Somephysicalinjuriescannotberepaired

Braindamage,amputation,spinalcord Physiotherapists,chiropractors,&occupationaltherapistshelp

dealwiththephysicaltrauma

• Whiplasho Occurswhenthemuscles&ligamentsofaperson’sneckaresprainedo Commoninjuryinrear‐endcollisionso Seatbelts&headrestsproperly

adjustedhelppreventtheheadfromflyingbackward

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• Griefo Feelingsofregret&sadnesso Passengersmaybeinjuredorkilledwhileyousurvive

PsychotherapistshelpdealwiththeemotionaltraumaProtection&Prevention

• SafeVehicleso InAB,everyonemustwearaseatbelto Peoplewere3x’saslikelytobeinjuredwithnoseat

beltvs.thosewhoworetheirseatbeltso OtherSafetyFeatures

Airbags Anti‐lockbrakingsystems Crumplezones Sideimpactbeams

• VehicleMaintenance

o Isimportantforallsafetyfeaturesonyourvehicle Tires Steering Windshieldwipers

• SafeRoads

o Rumplestripso Guardrailso Flashinglightsforpedestriansorintersections

Chapter14–TheNatureofSpeed–page250DefiningVelocity

• Distanceo Isachangeinpositiono Changeinpositionoccursoveraperiodoftime

• Velocityo Isthedistancetraveledduringaspecifictimeinterval

• CalculatingVelocity

o

o d=distanceinkilometers(km)ormeters(m)o t=timeinhours(h)orseconds(s)o v=velocityinkm/horm/s

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GraphingVelocity

• Distance/TimeGraphso Title

Describestheobjectbeingstudied Whatvariables(changingaspectsofthe

investigation)weremeasuredforthegrapho Axis

Showunitsforeachvariable X‐axis

• Showsthemanipulatedvariable• Thevariablechangedbythe

researcher Y‐axis

• Showstherespondingvariable• Measuredbytheresearcherasitchangesasaresultof

changestothemanipulatedvariableo Thelineofbestfitthatjoinsthedatapointsgivesinformationabout

thevelocity

• ConstantVelocity,ChangingVelocityo Astraightlineshowsconstantvelocityo Ajagged/curvedlineshowschangingvelocity

• CalculatingVelocityfromaDistance/TimeGraph

o

CalculatingDistance

• distance=velocityxtime=vxt

o v=velocityinkm/horm/so t=timeinhours(h)orseconds(s)

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DistanceTraveledduringReactionTime

• ReactionTime&StoppingDistanceo Brakingdistance

Thedistancethatavehicletravelsafterthedriverappliesthebrakes

o Stoppingdistance Includesthedistancetraveled

duringreactiontime+thebrakingdistance

o Followingdistance Asafefollowingdistancebehindothersis2seconds Ifnotpolicecanissueatailgatingticket

Chapter15–ThePhysicsofCollisions–page268

• Momentum&Masso Momentum

Isameasureofanobject’smotion&howlikelyitisthattheobjectwillremaininmotion

o Force Isanypushorpullonanobject.Thesizeoftheforcerequired

tomoveanobjectdependsonhowlongyouapplyforce,themassoftheobject,&howfastyouwanttomaketoobjectgo.

o CalculatingMomentum

momentum=massxvelocity =mxv

• m=massinkilograms(kg)• v=velocityinkm/horm/s• momentuminkilogrammeterspersecond(kg•m/s)

o SlowingMomentum

Braking• Applyaforcethatstopsvehiclesbydecreasingtheir

momentum• Usefriction

o Aforcethattwoobjectsexertoneachotherwhentheypressagainsteachother

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ChangingMomentumisRelatedtoForce

• Impulseo Thecombinationthesizeofforce&thetimeduringwhichtheforce

actso Changesmomentum‐eitherincreasingordecreasingo Thebiggertheimpulseis,thebiggerthechangeinmomentum

o MeasuringImpulse

impulse=forcextime=fxt

impulseismeasuredinkg•m/s f=forceinkg•m/s2ornewtons(N) t=timeinseconds(s)

o Impulse&Force

Impulseincreasesas• Forceisappliedoveralongperiodoftime• Alargeforceisapplied

Alargeimpulsecanchangemomentumagreatdealby• Applyingagreaterforce• Applyingaforceforalongerperiodoftime

• ChangingMomentumQuickly

o Faststopsrequirealargeimpulsethatresultsinanimmediatechangeinmomentum

Alargeamountofforceisrequired Forceiswhatcausesinjury&propertydamageduring

collisionsIsMomentumLost?

• ConservationofMomentum

o LawofConservationofMomentum Thetotalmomentumoftwocollidingobjectsstaysthe

sameaftertheircollision

• Head‐onCollisionso Totalmomentum=0o Positivemomentum&oppositemomentum

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Chapter16–TheTechnologyofSafety–page286HowSafetyFeaturesWork

• Theforceresultingfromacollisionissmallerifthechangeinmomentumoccursoveralongerperiodoftime

• Safetyfeaturesservetoslowdownthecollisioninorderforpassengerstoexperiencelessforce&fewerinjuries

• CrashTestDummiesareusedtodetermineo whatwillhappentopeopleduringacollisiono howwellcrumplezonesincarswork

SafetyFeatures Description Examples

CrumpleZones

‐Arepartsofthecarthataremadeofcrushablemetalorfiberglass

‐Slowdownthecollision‐Increasethetimeofthecollisionbetweentheoccupants&the

interiorofthevehicle;subsequently,reducingtheforceexperiencebythe

occupants

hood,doors,&trunk

RestrainingFeatures

OperationalFeatures

StructuralFeatures­RigidFeatures

StructuralFeatures­CrumpleZones

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• RoadSafetyFeatures

o Reducetheforceofacollisionbyslowingtheimpulseo Crashcushion

Barrelsfilledwithwaterorsandburstonimpact Placearoundpollsorsolidbarriers

o Guardrails Willbend,butnotbreaktolowerthemomentumofavehicle&

absorbtheforceofthecollision Preventthevehiclefromrollingoverorreboundingintotraffic Ifhitheadon,asectionwillsnapofftoslowthevehicle

Roll Cage

Side Impact Beams

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SeatBelts

• Designedtostopyourbodyfrombeingthrownforwardduringacollisiono 2‐pointbelts

alapbeltholdsapersonacrossthepelviso 3‐pointbelts

ashoulderharnessrestrainstheupperbodyaswell• Shouldcrossthepelvis&upperchest• Shouldbekeptsnug

o 4‐pointbelts Restrainsbothshoulders&distributetheforceover

moreofthechest Reducesstressontheribs,heart,&lungs

o Cannotrestrainaperson’sheadyet;therefore,youneedtoraisetheheadrest

o 1990 Albertaintroducedtheseatbeltlaw 90%ofAlbertansnowuseseatbelts

• HowSeatBeltsWork

o Webbing Polyesterornylon Stretch10to15%toallowthepassengertostopmore

gradually&feelasmallerforceo RetractorUnit

Involvesapendulum&aratchet

• ChildRestraintso Childrenhaveweakerbones&muscles

alongwithcomparativelyheavyheadso Devisesaredesignedtoprovideextra

protectionfortheirtypeofbody

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TheEvolvingAirBag

• AirBagso Rolledupinsidethesteeringwheel&thepassenger‐sidedashboardo Inacollision,achemicalreactioninsidethebagcausesittoinflatein

30millisecondso Theairinsidethecushionstheoccupants&slowstheirvelocity&

momentum

• SafetySystemsContinuetoImproveo AirBags

Firstgeneration• Causedmanyproblems

Secondgeneration• Deployatasaferspeed,atasafer

force,&workwiththeseatbelttoprotectoccupants

Thirdgeneration• Seatsensorsthatdetectthemass

oftheoccupant&adjusttheforceofthebagaccordingly

• Somehaveswitchessotheycanbeturnedoffwhenachildisinthefrontseat

o Modernseats Shapedlikeacatchersmitttocradlethebody

• Belts&airbagsshouldcatchyougentlybutfirmlyasyouflyforward

• Seats&raisedheadrestsshouldcatchyougentlybutfirmlyasyouflyback