PHY101: Major Concepts in Physics I
Transcript of PHY101: Major Concepts in Physics I
![Page 1: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/1.jpg)
Welcomebackto
PHY101:MajorConceptsinPhysicsI
Photo:J.M.Schwarz
![Page 2: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/2.jpg)
CourseWebpage:jmschwarztheorygroup.org/phy101/Thefirstthirdofthecoursescheduleispostedattheendofthesyllabus.Ourfirstin-classexamisscheduledforWednesday,October6.Wewillholdanin-classreviewsessionnextMonday,October4.
Lab:Lab3finishestoday.Lab4startstomorrow.Pleaselookoverthelabforabout10minutesbeforegoingtoyourlabsection.
Homework:HW4 isduethisFriday,October1, by3PMinyourTA’smailboxjustoutsideofPB201.
JoinourclassSlackpage:https://join.slack.com/t/phy101fall202-6yo4297/shared_invite/zt-vfuqm8l3-GxNF4Mj5uBe6c9WxmebNjw
Announcements
![Page 3: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/3.jpg)
3
Thirdsetofthreebigquestions
•Whatareforces?
• Whatlawsgovernforces?
• Howcanweapplythelawstosolveproblems?
![Page 4: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/4.jpg)
4
Tounderstandhowmotionisinduced,defineasystem.Forcescaninducemotion.
Simplyput,aforce isa“push”or“pull”onanobjectinasystem.
Forcesarevectors!
Wecandescribethisforceviaaforcediagram!
![Page 5: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/5.jpg)
Newton’sFirstLawNewton’sfirstlawofmotionForanobserverinaninertialreferenceframe,whennootherobjectsexertforcesonasystemorwhentheforcesexertedonthesystemaddtozero,thesystemcontinuesmovingatconstantvelocity(includingremainingatrest).
![Page 6: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/6.jpg)
Newton’sSecondLaw
Newton’ssecondlawTheacceleration ofasystemisproportionaltothevectorsumofallforcesbeingexertedonthesystemandinverselyproportionaltothemassmofthesystem:
on S 1 on S 2 on SS
S S
(3.6)F F Fam m
+ += =å
r r rr L
Herethesubscripts1and2standfortheobjectsexertingforcesonthesystem.Theaccelerationofthesystempointsinthesamedirectionasthevectorsumoftheforces.
⇀⇀ ……
⇀⇀⇀⇀
![Page 7: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/7.jpg)
Onelastforcelaw….
![Page 8: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/8.jpg)
ForcesComeinPairs:Newton’sThirdLaw
Whentwoobjectsinteract,object1exertsaforceonobject2.Object2inturnexertsanequal-magnitude,oppositelydirectedforceonobject1:
1 on 2 2 on 1 3( ).9F F= -r r
Notethattheseforcesareexertedondifferentobjectsandcannotbeaddedtofindthesumoftheforcesexertedononeobject.
⇀ ⇀
![Page 9: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/9.jpg)
Alargetruckcollideshead-onwithasmallcompactcar.Duringthecollision:
A.Thetruckexertsagreateramountofforceonthecarthanthetruckexertsonthecar.B.Thecarexertsagreateramountofforceonthetruckthanthetruckexertsonthecar.C.Thetruckexertsaforceonthecarbutthecardoesnotexertaforceonthetruck.D.Thetruckexertsthesameamountofforceonthecarasthecarexertsonthetruck.
QuickPollQuestion1
https://forms.gle/4j5tFXmzEe5UVC8q6
![Page 10: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/10.jpg)
Alargetruckcollideshead-onwithasmallcompactcar.Duringthecollision:
A.Thetruckexertsagreateramountofforceonthecarthanthetruckexertsonthecar.B.Thecarexertsagreateramountofforceonthetruckthanthetruckexertsonthecar.C.Thetruckexertsaforceonthecarbutthecardoesnotexertaforceonthetruck.D.Thetruckexertsthesameamountofforceonthecarasthecarexertsonthetruck.
QuickPollQuestion1
https://forms.gle/4j5tFXmzEe5UVC8q6
![Page 11: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/11.jpg)
Let’sdoanotherexampleproblem
Example3.7:Hairdryerscontainasmallpropellerthatpushesairawayfromthedryerthroughanozzle.Youplaceahairdryeronascalewiththenozzlepointingup,anditreads4.40N.Whenyouturnthehairdryeron,sothatthehairdryerispushingtheairupward,thereadingofthescaleincreasesto4.85N.Explainthechangethescalereading.
![Page 12: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/12.jpg)
Abookremainsatrestonatable.Whichofthefollowingistheforcepaired,accordingtoNewton'sThirdLaw,totheforcethatEarthexertsonthebook?A)Theforcethatthebookexertsonthetable.B)Theforcethatthetableexertsonthebook.C)TheforcethatthebookexertsonEarth.D)TheforcethattheEarthexertsonthetable.E)TheforcethatthetableexertsontheEarth.
QuickPollQuestion2
https://forms.gle/CsojSyxw156sb22b9
![Page 13: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/13.jpg)
Abookremainsatrestonatable.Whichofthefollowingistheforcepaired,accordingtoNewton'sThirdLaw,totheforcethatEarthexertsonthebook?A)Theforcethatthebookexertsonthetable.B)Theforcethatthetableexertsonthebook.C)TheforcethatthebookexertsonEarth.D)TheforcethattheEarthexertsonthetable.E)TheforcethatthetableexertsontheEarth.
QuickPollQuestion2
https://forms.gle/CsojSyxw156sb22b9
![Page 14: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/14.jpg)
14
Chapter3Textbookquestions
•Howdoseatbeltsandairbagssavelives?
• Ifyoustandonabathroomscaleinamovingelevator,doesitsreadingchange?
• Canaparachutistsurviveafalliftheparachutedoesnotopen?
![Page 15: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/15.jpg)
TwoNewBig Questions(Chapter4)
• Howdoesonedescribemotionintheplanewithconstantacceleration?
• HowdoesoneapplyNewton’slawsintheplane?
![Page 16: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/16.jpg)
Chapter4:ApplicationofNewton’sLaws
• Howdoesknowingphysicshelphumancannonballssafelyperformtheirtricks?
• Whowouldwinaracedownawaterslide:anadultorasmallchild?
• Howdoesfrictionhelpuswalk?
![Page 17: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/17.jpg)
OperationswithVectors• Thelengthofavectorarrowisthevector’smagnitude.
• Theorientationofeachvectorisdeterminedbythedirectionofthearrow.
• Avectorhasatail(thepointwhereitoriginates)andahead(thetipofthearrow).
• Theminussignusedinfrontofavectormeansthevectorhasthesamemagnitudeasapositivevectorbutpointsintheoppositedirection.
![Page 18: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/18.jpg)
OperationswithVectorsAddingvectors• Avectorcanbemovedfromonelocationtoanotheraslongasthereisnochangeinmagnitudeordirection.
• Tofindresultantofaddingtwovectors,thetailofonevectorisplacedattheheadofanothervector.
• Tofindresultantofaddinganynumberofvectors,thesameprocedureof“tailtohead”isusedforallofthem.
![Page 19: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/19.jpg)
OperationswithVectorsAddingvectors
Tailtoheadmethod
![Page 20: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/20.jpg)
OperationswithVectorsSubtractingvectors
Tailtoheadmethod
![Page 21: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/21.jpg)
Findingvectorcomponents
• Wecanreplaceanyforcewithtwoperpendicularforcesaslongastheperpendicularforcesgraphicallyaddtotheoriginalforce.
• Theperpendicularforcesarealongthex- andy-axisandarecalledthex- andy-vectorcomponentsoftheoriginalforce.
![Page 22: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/22.jpg)
Vectorcomponentstoscalarcomponents
• Theadvantagewithscalarcomponentsisthattheyarenumberswithsigns,whichcanbeaddedandsubtractedmoreeasilythanvectorquantities.
![Page 23: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/23.jpg)
Findingscalarcomponents
![Page 24: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/24.jpg)
Findingscalarcomponents
offorce,acceleration,velocity
![Page 25: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/25.jpg)
ProjectileMotion
Projectilesareobjectslaunchedatananglerelativetoahorizontalsurface.WecanuseNewton’ssecondlawtoanalyzeandexplaintheirprojectilemotion.
![Page 26: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/26.jpg)
ProjectileMotion
![Page 27: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/27.jpg)
ProjectileMotion
Areverticalaspectsofprojectilemotionindependentfromhorizontalaspects?
![Page 28: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/28.jpg)
ProjectileMotion
Areverticalaspectsofprojectilemotionindependentfromhorizontalaspects?
A. NoB. Yes
https://forms.gle/HUgYgR9tncbJA1pXA
![Page 29: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/29.jpg)
ProjectileMotion
Areverticalaspectsofprojectilemotionindependentfromhorizontalaspects?
Considerthefollowingtestingexperiment.
![Page 30: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/30.jpg)
ProjectileMotion
![Page 31: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/31.jpg)
ProjectileMotion
![Page 32: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/32.jpg)
QuantitativeProjectileMotion
![Page 33: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/33.jpg)
33
PMExampleProblem:Anobjectisprojectedfromtheorigin.Theinitialvelocitycomponentsarev0x =7.07m/s,andv0y =7.07m/s.Determinethexandypositionoftheobjectat0.2secondintervalsfor1.4seconds.Alsoplottheresults.
tvx
tatvy
ix
yiy
D=D
D+D=D 2
21
Since the object starts from the origin, Dy and Dx will represent the location of the object at time Dt.
![Page 34: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/34.jpg)
34
t (sec) x (meters) y (meters)0 0 0
0.2 1.41 1.220.4 2.83 2.040.6 4.24 2.480.8 5.66 2.521.0 7.07 2.171.2 8.48 1.431.4 9.89 0.29
PMExampleProblemcontinued:
![Page 35: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/35.jpg)
35
0
2
4
6
8
10
12
0 0.5 1 1.5
t (sec)
x,y
(m)
Thisisaplotofthexposition(bluepoints)andyposition(pinkishpoints)oftheobjectasafunctionoftime.
PMExampleProblemcontinued:
![Page 36: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/36.jpg)
36
PMExampleProblemcontinued:
0
0.5
1
1.5
2
2.5
3
0 2 4 6 8 10
x (m)
y (m
)
Thisisaplotoftheypositionversusxpositionfortheobject(itstrajectory).
Theobject’spathisaparabola.
![Page 37: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/37.jpg)
AnotherPMExampleProblemStephanieSmithHavensisshotfromacannonatspeed20m/s.Theendofthecannon’sbarrelis8.0mabovetheground,andthebarrelisorientedat53degreesabovethehorizontal.Stephanieenjoysherflightuntilshetouchesthenet,positioned2.0mabovegroundlevel.Thenetstretchestoreducetheforceexertedonherwhilestoppingher.
a) DeterminethetimeStephaniespendsinflight.b) Determinethehorizontaldistancefromtheendofthebarrel
wherethenetshouldbeplacedsothatshelandssafely.
![Page 38: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/38.jpg)
ProjectileMotion
Whatisthe timeofflightandtherange?
![Page 39: PHY101: Major Concepts in Physics I](https://reader034.fdocuments.in/reader034/viewer/2022051915/6284ece8412bc03fcf0342da/html5/thumbnails/39.jpg)
ProjectileMotion
Consideranothertestingexperiment.
Amovingcartthatverticallyejectsaball.