雨课堂学堂在线学堂云《Engineering Mechanics 工程力学（全英文）（北京理工）》单元测试考核答案

第1题Theresultantforceoftwointersectingforces

and

is

,i.e.,

.Themagnitudeof

mustbelargerthanthoseof

and

.第2题Aslongastwoforceshavethesamemagnitudeandareinoppositedirections,thesetwoforcesformacouple.第3题Foranycoplanarforcesystem,aslongasitsprincipalvectorisnotequaltozero,theforcesystemcanbereducedtoonesingleforce.第4题Asshownintheparallelogram,allforcesareatpointA.Inwhichfigure

FR

canbeconsideredastheresultantof

F1

and

F2?

ABCD第5题Neglecttheweightsofallmembers.InwhichcasebarBDisnotatwo-forcemember?

ABCD第6题Tostudythewholesystem,whichfree-bodydiagramiscorrect?

ABCD第7题Tostudythewholesystem,whichfree-bodydiagramiscorrect?ABCD第8题Tostudythewholesystem,whichfree-bodydiagramiscorrect?

ABCD第9题ForbarAD,whichfree-bodydiagramiscorrect?

ABCD第10题Inthisequilibriummechanism,thefree-bodydiagramofcrank

OA

canbedrawnasABCD正确答案：BCD第1题Anactionanditsreactionhavethesamemagnitudeandareinoppositedirectionsandcollinear,sotheyformanequilibriumforcesystem.第2题Allweightsandfrictionscanbeneglected.IfaforcePisappliedatthemid-pointofbarAB,inwhichcasethebarcanbeinaequilibriumstate?

ABCD第3题Arigidbodyisinequilibriumstateunderthecoplanarforcesystem.Whichsetofequilibriumequationsarenotindependentofeachother?ASF_x

=0,

SF_x

=0,

SM_A(F)=0BSM_O(F)=0,

SM_A(F)=0,

SM_B(F)=0CSM_O(F)=0,

SM_C(F)=0,

SF_y=0DSF_x=0,

SF_y=0,

SM_O(F)=0第4题Arigidbodyisinequilibriumstateunderthecoplanarforcesystem.Whichsetofequilibriumequationsarenotindependentofeachother?ASF_x=0,

SM_O(F)=0,

SM_A(F)=0BSM_O(F)=0,

SM_A(F)=0,

SM_B(F)=0CSM_A(F)=0,

SM_C(F)=0,

SF_y=0DSF_x=0,

SM_A(F)=0,

SM_B(F)=0第5题ConsidertheequilibriumofbarAB.ThecorrectmomentequationaboutpointAshouldbeASM_A(F)=m+Psinq

×

L/2+M+M_A=0BSM_A(F)=-m-Psinq

×

L/2+M=0CSM_A(F)=-mL-P

×

L/2+M+M_A=0DSM_A(F)=-m-Psinq

×

L/2+M+M_A=0第6题Considertheequilibriumofthewholesystem.Whichsetsofequilibriumequationsarecorrect?AåM_O(F)=-m-Fx_A×L×sinj

+Fy_A×L×cosj

-Q×2L×cosj

-P×

L×sinj

+F_B×3L×cosj

=0BåM_O(F)=-m-Q×2L×cosj

-P×

L×sinj

+F_B×3L×cosj

=0CåM_B(F)=-m-Fx_A×2L×sinj

-Fy_A×2L×cosj

+Q×L×cosj

=0DåM_B(F)=-m

-Fx_O×

L×sinj

-Fy_O×3L×cosj+

Q×L×cosj

=0正确答案：DB第7题Thewholesystemisinequilibriumstate.Whichsetofequilibriumequationsiscorrect?AStudy

ADB：

åM_A(F)=F_B×2L+Fy_D×L=0BStudythewholesystem：

åM_A(F)=-P×(L+r)+F_B×2L=0CStudy

CDEandthepully：

åM_D(F)=-P×r-T×(L–r)+Fx_E×L+F_BC×L×sin30°

=0DStudythewholesystem：

åM_A(F)=-P×(L+r)+F_B×2L-T×(L–r)=0第8题Aplanarmechanismconsistsofthreerigidbodiesandissubjectedtoaforcesysteminitsplane.Howmanyindependentequilibriumequationscanbecreatedatmost?A6B9C12D3第9题For

afree-bodydiagraminoneplane,whichsetsofequilibriumequationscouldbeindependentofeachother?AthreeforceequationsBtwoforceequationsandonemomentequationConeforceequationandtwomomentequationsDthreemomentequations正确答案：BCD第10题Thewholesystemisinequilibriumstate.Assumethememberforceinbar

i

(i=1,2,…5)isSi.Whichsetofequilibriumequationsiscorrect?AStudy

AB：

åM_A(F)=-q×L×L/2+S2

×L/2-P×3L/4=0BStudy

ABCDE：

åM_A(F)=-q×2L×L+S2

×L/2+S3×3L/2-P×3L/4+Fy_B×L+F_C×2L=0CStudy

BC：

åM_B(F)=-q×L×L/2–S3

×L/2–S5×L/2+F_C×L=0DStudy

ABCDE：

åM_A(F)=-q×2L×L-P×3L/4+F_C×2L=003Test第1题Themotionpathequationofapointiss=b+

ct,wherebandcareconstant.Whichstatementiscorrect?AThemotionpathmustbeastraightline.BThemotionpathmustbeacurve.CThespeedmustbeconstant.DTheaccelerationmustbezero.第2题Whichstatementiscorrectforamovingpoint?AIfat

isalwaysequalto

0andan

isnotequalto

0,thenthepointmovesalongacurvewithvaryingspeed.

BIfat

is

constant

andan

isnotequalto

0,thenthepointmovesalongacurvewithuniformlyvaryingspeed.CIfat

isnotequalto

0andan

isalwaysequalto

0,thenthepointmovesalongacurvewithvaryingspeed.DIfat

isnotequalto

0andan

isalwaysequalto

0,thenthepointmovesalongastraightlinewithconstantspeed.第3题Apointmovesalongacurvewithreducingspeed.Whichofthefourdrawingsforthevelocityandaccelerationispossible?ABCD第4题Apointmovesalongacirclewithpathcoordinate

s.Themotionequationofthepointcanbeexpressedas

.Whenthepointmovestothehighestpoint(M),the

x

and

y

coordinatesoftheaccelerationshouldbeABCD04Test第1题ThethreebarsO1A,O2BandABarepin-connectedinoneplane.Atthepositionshown,O1A//O2B.InwhichcasebarABundergoestranslationwhenbarsO1AandO2B

rotate

intheplane.ABCD第2题Ifarigidbodyundergoestranslation,thenthemotionpathofapointontherigidbodyAmustbeastraightline.Bmustbeaplanarcurve.Ccannotbeaspatialcurve.Dcouldbeaspatialcurve.第3题ThevelocitiesoftwoarbitrarypointsAandBonarigidbodyare

vA

and

vB,respectively.Whichstatementiscorrect?AIftherigidbodyisintranslation,then

½vA½=½vB½

mustbesatisfied.BIf

½vA½=½vB½

issatisfied,

thentherigidbodymustbeintranslation.CIftherigidbodyisintranslation,then

½vA½=½vB½

mustbesatisfiedandthedirectionsofthetwovelocitiescouldbedifferent.DIftherigidbodyisintranslation,then

thedirectionsof

vA

and

vB

mustbethesamebutprobably

|vA|¹|vB|.第4题Ifarigidbodyisrotatingaroundafixedaxis,thenAatsomeinstant,theaccelerationsofallpointsonalineperpendiculartotheaxisofrotationarenotparalleltoeachother.Batsomeinstant,thevelocitymagnitudesofanytwopointsareproportionaltotheirverticaldistancestotheaxisofrotation.Catsomeinstant,thevelocitiesofanytwopointsareparalleltoeachother.Ditisimpossiblethatthemotionpathsofallpointsarecirculararcs.第5题Aright-anglebarisrotatingaroundafixedaxis.Thedirectionsoftheangularvelocity

ω

andangularacceleration

α

areshowninthefigures.Whichonegivesthecorrectdirectionsforvelocity,normalandtangentialcomponentsofaccelerationofpointB?ABCD第6题Inthemechanism,

,

,

.Crank

rotateswithaconstantangularvelocity

inclockwisedirection.Atthepositionshown,points

,

and

areononeverticalline.Whichequationiscorrectforthevelocity/accelerationofpoint

or

?ABCD第7题ThedisksarerotatingaroundaxespassingthroughpointO.TheaccelerationsofpointMonthedisksareshown.Whichsetofequationsarecorrect?ABCD05Test第1题Incompositemotionofapoint,thetransportvelocityandaccelerationataninstantarethevelocityandaccelerationofthepointinthemovingreferenceframecoincidingwiththemovingpoint.第2题Howmanyunknownscanbesolvedforbasedonthevectorequation

Va=Ve+Vr?

A1B2C3D4第3题ThetheoremofcompositionofvelocitiesAis

onlyvalidwhenthetransportmotionisatranslation.Bisonlyvalidwhenthetransportmotionisarotation.Cisnotvalidwhenthetransportmotionisarotation.Disvalidforanytypeoftransportmotion.第4题Inthevelocityparallelogramdrawnbasedonthetheoremofcompositionofvelocities,Athe

absolutevelocityisdiagonaloftheparallelogramformedbythetransportvelocityandrelativevelocity.Bthetransportvelocityisdiagonaloftheparallelogramformedbytheabsolutevelocityandrelativevelocity.Ctherelativevelocityisdiagonaloftheparallelogramformedbythetransportvelocityandabsolutevelocity.Dthealgebraicsumoftheprojectionsoftheabsolutevelocity,transportvelocityandrelativevelocityonanyaxisisequaltozero.第5题Inthemechanism,barOArotateswithangularvelocity

w

incounterclockwisedirection.WhichvelocityparallelogramiscorrectifpointBonbarBCDischosenasthemovingpointandthemovingreferenceframeisattachedtobarOA?ABCD第6题Inthemechanism,thediskrotateswithangularvelocity

w

incounterclockwisedirection.WhichvelocityparallelogramiscorrectifpointAonbarABischosenasthemovingpointandthemovingreferenceframeisattachedtothedisk?ABCD第7题CrankOArotateswithangularvelocity

w

andangularacceleration

α.TheaccelerationsaredrawninthefigureifpointAoncrankOAischosenasthemovingpointandthemovingreferenceframeisattachedtotheT-shapedmember.Whichequationiscorrectaccordingtothetheoremofcompositionofaccelerations?ABCD06Test第1题Points

and

areanytwoarbitrarypointsinaplanefigure.Theprojectionsofthevelocitiesofthesetwopointsonline

are

and

,respectively.

Theprojectionsofthe

accelerations

ofthesetwopointsonline

are

and

,respectively.Thenwecanget

and

.第2题Theplanarmotionofarigidbodycanberesolvedintoatranslationandarotation.Theangularvelocityandangularaccelerationwithrespecttobasepoint

are

and

,respectively.Theangularvelocityandangularaccelerationwithrespecttobasepoint

are

and

,

respectively.Whichsetofthefollowingequationsiscorrect?ABCD第3题Fortheplanarmechanismatthepositionshown,bar

isinhorizontaldirectionandbar

isinverticaldirection.Atthisinstant,thevelocityandaccelerationofslider

are

and

,respectively;theangularvelocityandangularaccelerationofbar

are

and

,respectively;

theangularvelocityandangularaccelerationofbar

are

and

,respectively.

Whichsetofthefollowingequationsiscorrect?ABCD第4题Points

and

areanytwoarbitrarypointsinaplanefigure.

Atainstant,thevelocitiesofthesetwopoints

are

and

,respectively;

The

accelerationsofthesetwopoints

are

and

,respectively.Which

of

thefollowingequationsiscorrect?ABCD正确答案：AD第5题Atainstant,themagnitudesofvelocitiesofpoints

and

inaplanefigureare

and

,respectively,and

.

Whichdrawingsareimpossibleforthevelocitydirections?ABCD正确答案：DA第6题Therelationsofvelocitiesofpoints

and

inthecrank-connectingrodmechanismareshown.Whichonecouldbecorrect?ABCD第7题Whicharethecorrectmethodstocalculatetheangularvelocity

ofbar

inthemechanism?ABCD正确答案：ABD第8题Intheplanarmechanism,thethreebars(,

and

),wheel

andslider

arepin-connectedtogether.Bar

rotatesaroundpoint

.Wheel

rotateswithoutslippingonthehorizontalsurface.Slider

movesinverticaldirection.Whichstatementsarecorrect?APoint

istheinstantaneouscenterforvelocitiesofwheel

.BPoint

istheinstantaneouscenterforvelocitiesofbar

.CPoint

istheinstantaneouscenterforvelocitiesofbar

.DPoint

istheinstantaneouscenterforvelocitiesofbar

.正确答案：ACD第9题Intheplanarmechanism,thesmallgear

rotateswithoutslippingonthebigfixedgear

.Crank

rotatesaroundpoint

.Bar

ispin-connected

togear

andbar

.Whichstatementsarecorrect?AThecontactpoint

ofthetwogearsistheinstantaneouscenterforvelocitiesofgear

.BPoint

istheinstantaneouscenterforvelocitiesofgear

.CPoint

istheinstantaneouscenterforvelocitiesofbar

.

DPoint

istheinstantaneouscenterforvelocitiesofbar

.正确答案：AD第10题Aplanefiguremovesinitsplane.Thevelocityvectorsoftwodifferentpointsontheplanefigurearethesameatainstant.Whichstatementsarecorrect?AAllpointsintheplanefigurehavethesamevelocityatthisinstant.BAllpointsintheplanefigurehavethesameaccelerationatthisinstant.CTheangularaccelerationoftheplanefiguremustbezero,buttheangularvelocitymaynotbezeroatthisinstant.DTheangularvelocityoftheplanefiguremustbezero,buttheangularaccelerationmaynotbezeroatthisinstant.正确答案：AD07Test第1题A

particleissubjectedtoforcesof

,

,

¼

and

,andtheresultantoftheseforcesis

.

Whichstatementiscorrect?AThemovingdirectionoftheparticlemustbethesameasthatoftheresultantforce

.BThegreatertheresultantforce

,thegreaterthespeedoftheparticle.CThegreatertheresultant

force

,

thegreaterthe

acceleration

ofthe

particle.DTheaccelerationdirectionoftheparticlemayormaynotbethesameasthatoftheresultantforce

.第2题Acarpassesthroughpoints

,

and

onaroad.Thepressuresontheroadfromthecar

are

,

and

，respectively,thenABCD第3题Aspherewithweight

issuspendedbytwocables

and

.Basedonequilibriumanalysis,thetensileforceinthetwocablesshouldbe

.Ifcable

iscutsuddenly,thetensileforceincable

willbe

atthisinstant.Whichstatementiscorrect?ABCD第4题Asshown,acannonballwithmassmisfiredwithinitialvelocity

andemissionangle

.Theairresistanceisproportionaltothe

cannonball

velocity,i.e.,

,where

isaconstant.ThedifferentialequationofmotionofthecannonballcanbeABCD08Test第1题Fortwoparticleswithmassesof

and

，theirspeedsatsomeinstantare

and

，respectively.Whichstatementiscorrect?AIf

and

，themomentaofthesetwoparticlesmustbethesame.BIf

and

，themomentaofthesetwoparticlescanalsobethesame.CIfand

，themomentaofthesetwoparticlescanalsobethesame.DIfand

，themomentaofthesetwoparticlesmustbedifferent.第2题Amovingrigidbodywithmass

hasamomentum

andmasscentervelocity

,then

shouldbesatisfied.第3题Threehomogeneousdisks

,

and

havethesameradius

,thesameweight

andthesameangularvelocity

.Asshown,disk

rotatesarounditsmasscenter;disk

rotatesaroundafixedaxisonitsedge;diskrotateswithoutslippingonahorizontalsurface.Ifthemomentaofthethreedisksare

,

and

,respectively,thenABCD第4题Ahomogeneousbar

hasaweight

.Oneendofthebarcontactswiththesmoothgroundandtheotherendissuspendedbyacable.Ifthecableiscutatthepositionshown(),thenAThemotionpathofthemasscenter

willbeacirculararcduringthesubsequentmotion.B

whenthebarfallstotheground.C

whenthebarfallstotheground.D

whenthebarfallstotheground.第5题Ahomogeneousdiskrestsonasmoothhorizontalsurface.Ifacoupleformedby

and

isappliedonthedisk,thereshouldbenodisplacementforthediskcenter.第6题Whichstatementiscorrect?AThemomentaofasystemofparticlesmustbelargerthanthemomentumofoneparticleinthesystem.BThemomentumofeachparticleinasystemisequaltozero,thenthemomentaofthewholesystemmustbeequaltozero.CThemomentumofeachparticleinasystemisnotequaltozero,thenthemomentaofthewholesystemmustnotbeequaltozero.DThemagnitudeofthemomentumofaparticlesystemmustbeequaltothesummationofthemagnitudesofthemomentaofallparticlesinthesystem.09Test第1题Ahomogeneousdiskwithmass

M

andradius

R

isrotatingaroundanaxispassingthroughpoint

O.TheangularmomentumofthediskaboutthisaxisshouldbeABCD第2题Ahomogeneousdiskwithmass

M

andradius

R

isrotatingwithoutslippingalonganinclinedplane.Thevelocityofthediskcenteris

V.Theangularmomentumofthediskabouttheitscontactpoint

C

withtheplaneshouldbeABCD第3题Asshown,

-axispassesthroughthemasscenterofonebodywithmass

m.

-and

-axesareparallelto

-axis.Thedistancesbetween

-and

-axes,

-and

-axes,and

-and

-axesare

a,

b

and

d,respectively.Basedon

theparallel-axistheoremformassmomentofinertia,wecangetABCD第4题Aslenderbarwithmass

iscomposedoftwohomogeneoussegments,whicharemadeofsteelandwood,respectively.Themassmomentofinertiaofbarabout

-,

-and

-axesare

,

and

,respectively.ThenwecangetABCD第5题Thetwowheels

and

havethesamemassmomentofinertia.Ablockwithweight

issuspendedonwheel

andaforce

isappliedonwheel

.

.Iftheangularaccelerationsofthetwowheelsare

and

,respectively,then

mustbeequalto

.第6题Thehomogeneouspullyhasamass

andradius

.BlockAofmass

andblock

ofmass

aresuspendedonthepullythroughaweightlesscable.Iftheangularacceleration

ofthepullyisinclockwisedirection,thenthedifferentialequationofrotationofthepullyshouldbeABCD第7题ThetwohomogeneousringsinFigs.(a)and(d)andthetwohomogeneousdisksinFigs.(b)and(c)havethesameweight

andradius

.Force

isappliedinFigs.(a)and(b).Amoment

isappliedinFig.(c).Ablockwithweight

issuspendedinFig.(d).Whichstatementiscorrect?ATheangularaccelerationoftheringinFig.(a)isequaltothatofthediskinFig.(b).BTheangularaccelerationoftheringinFig.(a)isequaltothatofthediskinFig.(c).CTheangularaccelerationoftheringinFig.(a)isequaltothatoftheringinFig.(d).DTheangularaccelerationofthediskinFig.(b)isequaltothatoftheringinFig.(d).第8题AhomogeneousdiskCwithweight

P

andradiusrisrotatingaroundpointOwithangularvelocity

w.TheeccentricityisOC=e.TheangularmomentumofthediskaboutpointOshouldbeABCD10Test第1题The

undeformed

lengthofaspring

is

.Oneendofthespringisfixedandtheotherendisattachedtoablock.Whentheblockmovesfrom

point

to

,frompoint

to

andfrompoint

to

,theworkdonebythespringforceis

,

and

,respectively.Whichofthefollowingiscorrect?ABCD第2题Asmallspheremovesfrompoint

topoint

alongacircularpathinaverticalplane.Ifitmovesalongpath

,theworkdonebyitsgravityforce

is

.Ifitmovesalongpath

,theworkdonebyitsgravityforceis

.ThenwecangetABCD第3题Ahomogeneousbarhasmassmandlength

.Atthepositionshown,theangularvelocityofthebaris

.Thevelocitiesofpoints

,

and

are

,

and

，respectively.Point

istheinstantaneouscenterforvelocitiesofthebar.ThekineticenergyofthebaratthisinstantshouldbeABCD第4题Asmallsphere

withmassmmovesfromthesameheighttothegroundalongthreedifferentpaths.Itisassumedthattheinitialvelocityiszeroandallfrictionscanbeneglected.Ifthemagnitudesofvelocitiesofthespherewhenitreachesthegroundare

,

and

，respectively,thenABCD第5题Twoblocks

and

connectedbyaspringareputonahorizontalsmoothsurface.Thespringiscompressedandthenreleasedfromrestsuddenly.Ifthekineticenergyandmomentumofthesystemare

and

,respectively,thenABCD第6题Asmallspherewithmassmmovesalongasmoothsemi-circularpath

.Theinitial

velocity

pointsdownward.Whichofthefollowingstatementsarecorrect?AThemomentaofthespherearethesameatpoint

andpoint

.BThemomentaofthesphereare

differentat

point

andpoint

.CThe

kineticenergies

ofthesphereare

thesameatpoint

andpoint

.DThekineticenergiesofthesphereare

differentat

point

andpoint

.正确答案：BC第7题Asmallspherewithmassmmovesalongasmoothsemi-circularpath

.Theinitialvelocity

pointsdownward.Whichofthefollowingstatementsarecorrect?AThemomentumisnotconservedduringthemotion.BThe

angularmomentumaboutpoint

is

conservedduringthemotion.CTheangularmomentumaboutpoint

is

notconserved

duringthemotion.DThemomentum

is

conservedduringthemotion.正确答案：AC第8题Thekineticenergyofarigidbodyinplanemotioncanbedeterminedbyone-halfoftheproductofitsmassandthesquareofits

velocityatthecentroid.第9题Theinternalforceof

a

particlesystemcanchangethekineticenergyoftheparticle

system.第10题Thethreehomogeneousrigidbodies(ring,diskandbar)havethesamemass.Theyareallreleasedfromrestfromthedashlinepositions,i.e.,theirmasscentersandpoint

areinahorizontalline.Ifthevelocitiesoftheirmasscentersare

,

and

,respectively,whentheymovetothelowestposition,thenABCD11Test第1题Aprincipalvector

andprincipalmoment

canbeobtainedbyreducinganinertialforcesystemtoonepoint(reductioncenter).Whichstatementsarecorrect?ATheprincipalvector

dependsonthepositionofthereductioncenter.BTheprincipalmoment

dependsonthepositionofthereductioncenter.CTheprincipalvector

doesn’tdepend

onthepositionofthereductioncenter.DTheprincipalmoment

doesn’tdependonthepositionofthereductioncenter.正确答案：BC第2题Twoblockswith

weights

and

aresuspendedonahomogeneouspulleywithweight

byaweightlesscable.

.Amoment

isappliedonthepulleyandthewholesystemisinastationarystate.Thecableforcesonblocks

and

are

and

,respectively.Ifthemoment

isremovedsuddenly,then

mustbelargerthan

providedthereisnorelativeslidingbetweenthecableandthepulley.第3题Underahorizontalforce

,twoblockswith

masses

and

()aremovingonasmoothsurface.ThetwoblocksinFig.(a)areacceleratingandthetwoblocksinFig.(b)aredecelerating.Iftheforceexertedonblock

byblock

is

,

then

mustbelargerthan

.第4题Aparticleissubjectedtoitsgravityforceonly.Theinertialforceis

whentheparticleisinfreefallingmotion.

Theinertialforceis

whentheparticleis

thrownupright.WecanhaveABCD第5题Under

aforce

appliedatpoint

,thetrolleywithweight

ismovingwithacceleration

a

onahorizontalsurface.Point

isthemasscenterofthetrolley.By

D’Alembert’s

Principle,theinertialforceonthetrolleyshouldbeABCD第6题Ahomogeneousslenderbar

withlength

andmass

rotatesaroundpoint

.Atthepositionshown,bar

has

an

angularvelocity

and

angularacceleration

.TheinertialforcesystemcouldbeABCD第7题Ahomogeneous

wheel

with

mass

andradius

rotates

withoutslippingonahorizontalsurface.Point

istheinstantaneouscenterforvelocities

ofthewheel.The

acceleration

ofthewheelcenter

is

.

TheinertialforcesystemcouldbeABCD正确答案：BD12Test第1题Basedontheisotropyassumption,inalldirectionsthematerialhasthesameAstressBdeformationCdisplacementDmechanicalproperties第2题Whichstatementiscorrect?AThe

internalforce

on

acrosssectionofabaristhe

algebraicsummationofthestresseson

thiscrosssection.BThestressonacrosssectionofabaristheaverageinternalforceonthiscrosssection.

CStressistheintensityoftheinternalforce.DTheinternalforcemustbelargerthanthestress.第3题TherelationshipbetweeninternalforceandstressisthatATheinternalforceissmallerthanthestress.BTheinternalforceis

thealgebraicsummationofthe

stress.

CTheinternalforceisavectorandthestressisascalar.

DThestressistheinternalforceperunitarea.

第4题Themagnitudeoftheinternalforceofabardependsonnotonlytheexternalforcebutalsotheshapeofitscrosssection.第5题Thestressistheintensityoftheinternalforceperunitarea.13Test第1题Thevolumeelementdeformsfromthesolidlinepositiontothedashlineposition.Theshearstrainmustbe

.14Test第1题Hooke’slawcanbeusedforAductilematerialsonly.

Baxialtensiononly.Cacasewiththestresssmallerthantheproportionallimit.Dacasewiththestresssmallerthantheyieldingstress.第2题Afterstrainhardening(coldhardening),thematerialshowsAhigherproportionallimitandlowerductility.Bhigher

proportionallimit

andductility.Clowerproportional

limitand

higherductility.Dlowerproportional

limitand

ductility.15Test第1题The

crosssection

areaofabarintensionis

A.Thenormalstress

ontheinclinedplanewithinclinedangle

shouldbeABCD第2题Theaxialloadonsectionn-nofthebarshouldbeA-3PB-4PC4PD8P第3题Forabarunderaxialtension,thesectionswiththemaximumnormalstressandmaximumshearstressareAthecrosssectionandinclinedsectionwithinclined

angle45°,respectively.Bboththecrosssections.Ctheinclinedsectionwithinclinedangle45°andcrosssection,

respectively.Dboththe

inclined

sections

withinclinedangle45°.第4题ThemaximumtensileforceinthebarshouldbeA12KNB20KNC8KND13KN第5题Ifthetotalelongationofabariszero,thentheremustbenodisplacementforeachcrosssectionofthebar.第6题Twobarsmadeoftwodifferentmaterialshavethesamelengthandcrosssectionarea.Iftheaxialloadsinthetwobarsarethesame,thenthestressesontheircrosssectionsmustbealsothesame.第7题Onewoodenbarandonesteelbarhavethesamecrosssection.Iftheexternalforcesonthesetwobarsarethesame,thentheinternalforcesinthesetwobarsshouldbealsothesame.第8题Thetensilerigidityofthebarwithlength2l

is

EA.ThetotalelongationofthebarshouldbeABCD第9题Thebarissubjectedtoaforceasshown.Oneendofthebarisfixed.Whichstatementiscorrect?AThereisnodeformationinsegmentAB.BThereisnodeformationinsegment

BC.CThereisnodisplacementforanycrosssectioninsegment

AB.DThereisnodisplacementforanycrosssectioninsegment

BC.第10题ThebarwithaslotinsegmentBCissubjectedtotensileloading.WhichofthefollowingiscorrectfortheaxialforcesandstressesinsegmentABandBC?ABCDNoneoftheseiscorrect.16Test第1题Ahollowshaftissubjectedtoanexternaltorque.Whichofthefollowingfiguresiscorrectfortheshearstressdistributiononthecrosssectionoftheshaft?ABCD第2题Whichiscorrectforthesignsoftheinternaltorquesintheshaftshown?ATheinternaltorqueispositiveinsegment

AB

andnegativeinsegment

BC.BTheinternaltorqueis

negativein

segment

AB

and

positivein

segment

BC.CTheinternaltorquesinsegments

AB

and

BC

arepositive.DTheinternaltorquesinsegments

AB

and

BC

are

negative.第3题ThefactorsaffectingthemagnitudeoftheangleoftwistofacircularshaftincludeAtheinternaltorque,materialandlengthoftheshaft.Btheinternaltorque,

length

and

torsionalrigidity(GJ)of

the

shaft.Ctheinternaltorque,materialand

crosssectiongeometry

ofthe

shaft.Dthe

internaltorque,lengthandcrosssectiongeometry

of

theshaft.第4题TheinnerandouterdiametersofahollowcircularshaftaredandD,

respectively.

a=d/D.ThepolarmomentofinertiaoftheshaftshouldbeABCD第5题Asolidcircularshaftissubjectedtoanexternal

torque

Mn.Iftheshaftisinlinearelasticregion,theshearstressdistributiononitscrosssectionshouldbeABCD第6题Twocircularshaftswiththesamelengtharesubjectedtothesameexternaltorque.Thediameterofthefirstshaftisonehalfofthatofthesecondone.TheratioofthemaximumshearstressesinthesetwoshaftsshouldbeA2:1B4:1C8:1D16:1第7题Ifacircularshaftisundertorsion,thenthereshouldbeonlyshearstressesandnonormalstressesonitscrosssection.第8题Ifacircularshaftisundertorsion,then

allpointshavingthesamedistancetothecrossse