OA06a Torque, Equilibrium; Work, Energy PDF

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21/09/2016

OA06a:Torque,Equilibrium;Work,Energy

OA06a:Torque,Equilibrium;Work,Energy Due:11:59pmonWednesday,September21,2016 Youwillreceivenocreditforitemsyoucompleteaftertheassignmentisdue.GradingPolicy

PrelectureVideo:StaticEquilibriumandCenterofMass ClickPlaytowatchthevideo.Answertheungradedquestionsinthevideoandthegradedfollowupquestionsatright.

PartA Anextendedobjectisinstaticequilibriumif__________. ANSWER: eitherthenetforceactingontheobjectiszeroorthenettorqueactingontheobjectiszero onlythenettorqueactingontheobjectiszero onlythenetforceactingontheobjectiszero boththenetforceactingontheobjectiszeroandthenettorqueactingontheobjectiszero

Correct Anextendedbodyisinstaticequilibriumwhenthenetforceandthenettorqueactingonitarebothzero.

PartB Whichofthefollowingobjectsisinstaticequilibrium? Selectallthatapply ANSWER:

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OA06a:Torque,Equilibrium;Work,Energy

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Correct Boththesumoftheforcesandthesumofthetorquesmustbezeroforanextendedbodytobeinstatic equilibrium.

PartC Twochildrenwanttobalancehorizontallyonaseesaw.Thefirstchildissittingonemetertotheleftofthepivotpoint locatedatthecenterofmassoftheseesaw.Thesecondchildhasonehalfthemassofthefirstchild.Whereshould thesecondchildsittobalancetheseesaw? ANSWER: 

totherightofthepivot



totherightofthepivot

 

totherightofthepivot totherightofthepivot

Correct Whethertheseesawisbalancedornotdependsuponwhetherthereisanynettorqueaboutitspivotpoint.This canbedeterminedeitherbyexplicitlycalculatingthetorqueduetoeachchildaboutthatpoint,orbyfindingthe locationofthecenterofmassofthetwochildren.Ifthecenterofmassisnotdirectlyabovethepivotpoint,there willbeanettorqueaboutthatpoint.

PartD https://session.masteringphysics.com/myct/assignmentPrintView?assignmentID=4779899

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OA06a:Torque,Equilibrium;Work,Energy

Rankinorder,fromleaststabletomoststable,thethreeglassesofwatershown. Ranktheglassesfromleaststabletomoststable.Iftwoglasseshavethesamestability,placeoneontopof theother. ANSWER:

Reset

Help

 



Correct Stabilityisimprovedbywideningthebaseofsupportandloweringthecenterofmass.

Problem12.12

PartA Findthetensionintheleftwiresupportingthetrafficlightshowninthefigure. Assume =48 , =42 and =31 . Expressyouranswertotwosignificantfiguresandincludetheappropriateunits.

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ANSWER: = 230

Correct

PartB Findthetensionintheright. Expressyouranswertotwosignificantfiguresandincludetheappropriateunits. ANSWER: = 200

Correct

Problem12.10 A71

adultsitsatoneendofa9.4 longboard.His26

childsitsontheotherend.

PartA Whereshouldthepivotbeplacedsothattheboardisbalanced,ignoringtheboard'smass? Expressyouranswerusingtwosignificantfigures. ANSWER: = 2.5 

fromadult

Correct

PartB Findthepivotpointiftheboardisuniformandhasamassof15 https://session.masteringphysics.com/myct/assignmentPrintView?assignmentID=4779899

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OA06a:Torque,Equilibrium;Work,Energy

Expressyouranswerusingtwosignificantfigures. ANSWER: = 2.8 

fromadult

Correct

Problem12.22 Auniformsteelbeamhasamassof900

.Onitisrestinghalfofanidenticalbeam,asshowninthefigure.

PartA Whatistheverticalsupportforceatleftend? Expressyouranswertotwosignificantfiguresandincludetheappropriateunits. ANSWER: = 7700

Correct

PartB Whatistheverticalsupportforceatrightend? Expressyouranswertotwosignificantfiguresandincludetheappropriateunits. ANSWER: = 5500

Correct

Problem12.28 A53.0

personstands2.0

fromthebottomofthestepladdershowninthefigure.

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PartA Determinethetensioninthehorizontaltierod,whichishalfwayuptheladder.Ignorethemassoftheladderand assumethegroundisfrictionless.[Hint:Considerfreebodydiagramsforeachsectionoftheladder.] Expressyouranswerusingtwosignificantfigures. ANSWER: = 160  

Correct

PartB Determinethenormalforcethegroundexertsontherightsideoftheladder. Expressyouranswerusingtwosignificantfigures. ANSWER: = 210  

Correct

PartC Determinethenormalforcethegroundexertsontheleftsideoftheladder. Expressyouranswerusingtwosignificantfigures. ANSWER: = 310  

Correct

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PartD Determinetheforce(magnitude)thattheleftsideoftheladderexertsontherightsideatthehingeonthetop. Expressyouranswerusingtwosignificantfigures. ANSWER: = 260  

Correct

PartE Determinethedirectionifthisforce. Expressyouranswerusingtwosignificantfigures. ANSWER: = 52  clockwisefromtherightdirection

Correct

Problem7.1

PartA Howmuchworkisdonebythegravitationalforcewhena230

piledriverfalls2.40

?

Expressyouranswerusingtwosignificantfigures. ANSWER: = 5400  

Correct

Problem7.59 A1500 carrollingonahorizontalsurfacehasspeed =61 broughttorestinadistanceof2.1 .

whenitstrikesahorizontalcoiledspringandis

PartA Whatisthespringconstantofthespring? Expressyouranswerusingtwosignificantfigures. ANSWER: = 9.8×104 



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Correct

Problem7.19

PartA Aspringwithaspringconstantof2500N/m.isstretched4.00cm.Whatistheworkrequiredtostretchthespring? ANSWER: 0J 4.00J 1.00J 3.00J 2.00J

Correct

ConceptualQuestion7.18

PartA Apersonappliesaconstantforceonanobjectofmass20kgthatcausestheobjecttomovehorizontallyataconstan speedof0.20m/sthroughadistanceof0.80m.Whatistheworkdoneontheobject? ANSWER: 16J 160J 0J 10J Cannotbedeterminedwithoutknowingthemagnitudeoftheappliedforce.

Correct

ConceptualQuestion7.21

PartA Aconstantforceisappliedtoanobjectthatcausesacertaindisplacement.Iftheanglebetweentheforceandthe displacementis135°,theworkdonebythisforceis ANSWER:

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positive. negative. 0J. Cannotbedeterminedwithoutknowingthemagnitudeofthedisplacement. Cannotbedeterminedwithoutknowingthemagnitudeoftheappliedforce.

Correct

ConceptualQuestion7.15

PartA Theworkdonebythecentripetalforceonanobjectwithamassof1kgmovingwithaconstantvelocityof4m/sinto circularpathofradius0.6mforonefullcycleis ANSWER: 3.8J 40J 0J 100.7J 80J

Correct

ConceptualQuestion7.16

PartA Doesthecentripetalforceactingonanobjectdoworkontheobject? ANSWER: No,becausetheobjecthasconstantspeed. Yes,sinceaforceactsandtheobjectmoves,andworkisforcetimesdistance. No,becausetheobject'sdisplacementiszero. Yes,sinceittakesenergytoturnanobject. No,becausetheforceandthedisplacementoftheobjectareperpendicular.

Correct ScoreSummary: Yourscoreonthisassignmentis99.2%. Youreceived143.77outofapossibletotalof145points.

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