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PHYS 141 EXAM 2 CONCEPT QUESTIONS WITH COMPLETE ANSWERS.
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PHYS 141 EXAM 2 CONCEPT QUESTIONS WITH COMPLETE ANSWERS.
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PHYS 141 EXAM 2 CONCEPTQUESTIONS WITH COMPLETE
ANSWERS
The ffmass ffof ffthe ffmoon ffis ff1/81 ffof ffthe ffmass ffof ffthe ffearth. ffCompared ffto ffthe
ffgravitational ffforce ffthat ffthe ffearth ffexerts ffon ffthe ffmoon, ffthe ffgravitational ffforce ffthat
ffthe ffmoon ffexerts ffon ffthe ffearth ffis ff- ffAnswer ffequally ffstrong.
Compared ffto ffthe ffearth, ffa ffdistant ffplanet ffhas fftwice ffthe ffmass ffand fftwice ffthe
ffradius. ffThis ffmeans ffthat ffcompared ffto ffthe ffearth's ffsurface ffgravity, ffthe ffsurface
ffgravity ffon ffthe ffother ffplanet ffis ff- ffAnswer ffhalf ffas ffmuch.
A ffbox ffis ffsitting ffin ffthe ffback ffof ffthe fftruck. ffThe fftruck ffbegins ffto ffaccelerate ffforward
ff(to ffthe ffright) ffand ffthe ffbox ffdoes ffnot ffslip. ffIn ffa fffree-body ffdiagram fffor ffthe ffbox,
ffthe ffforce ffof fffriction ffon ffthe ffbox ffpoints ff- ffAnswer ffto ffthe ffright.
A ffcable ffattached ffto ffa ffcar ffholds ffthe ffcar ffat ffrest ffon ffthe fffrictionless fframp. ffThe
fframp ffexerts ffa ffnormal ffforce ffon ffthe ffcar. ffHow ffdoes ffthe ffmagnitude ffFn ffof ffthe
ffnormal ffforce ffcompare ffto ffthe ffweight ffof ffthe ffcar? ff- ffAnswer ffFn ff< ffw
An ffobject ffis ffthrown ffup ffin ffthe ffair. ffIs ffthe ffobject ffin ffmomentary ffequilibrium ffwhen
ffit ffreaches ffits ffhighest ffpoint? ff- ffAnswer ffNo, ffnever.
*equilibrium ff= ffzero ffacceleration*
You ffpress ffyour ffphysics ffbook ffflat ffagainst ffa ffvertical ffwall ffwith ffyour ffhand. ffYour
ffarm ffremains ffhorizontal. ffWhat ffis ffthe ffdirection ffof ffthe fffriction ffforce ffexerted ffby ffthe
ffwall ffon ffthe ffbook? ff- ffAnswer ffupward
You ffdrive ffa ffrace ffcar ffaround ffa ffcircular fftrack ffof ffradius ffR ffat ffa ffconstant ffspeed ffof
ffv. ffIf ffyou ffthen ffdrive ffthe ffsame ffcar ffaround ffa ffdifferent ffcircular fftrack ffof ffradius ff2R
ffat ffa ffconstant ffspeed ffof ff2v, ffyour ffacceleration ffwill ffbe ff- ffAnswer fftwice ffas ffgreat.
Consider ffthe fffollowing ffsituations:
(i) ffA ffminivan ffis fffollowing ffa ffhairpin ffturn ffon ffa ffmountain ffroad ffat ffa ffconstant ffspeed
ffof fftwenty ffmiles ffper ffhour.
(ii) ffA ffparachutist ffis ffdescending ffat ffa ffconstant ffspeed ffof ff10 ffm/s. ff
(iii) ffA ffheavy ffcrate ffhas ffbeen ffgiven ffa ffquick ffshove ffand ffis ffnow ffsliding ffacross ffthe
fffloor. ffThere ffis fffriction ffbetween ffthe ffcrate ffand fffloor.
(iv) ffA ffchild ffis ffswinging ffback ffand ffforth ffon ffa ffswing ffat ffthe ffpark.
, (v) ffA fffootball ffthat ffwas ffkicked ffis ffflying ffthrough ffthe ffgoal ffposts. ff
In ffwhich ffone ffof ffthese ffsituations ffdoes ffthe ffobject ffor ffperson ffexperience ffzero
ffacceleration? ff- ffAnswer ffii ffonly
A ffping-pong ffball ffis ffshot ffinto ffa ffcircular fftube ffthat ffis fflying ffflat ff(horizontal) ffon ffa
fftabletop. ffWhen ffthe ffping-pong ffball ffleaves ffthe fftrack, ffwhich ffpath ffwill ffit fffollow? ff-
ffAnswer ffThe ffpath fftangential ffto ffthe fftabletop
A ffpendulum ffbob ffof ffmass ffm ffis ffattached ffto ffthe ffceiling ffby ffa ffthin ffwire ffof fflength
ffL. ffThe ffbob ffmoves ffat ffa ffconstant ffspeed ffin ffa ffhorizontal ffcircle ffof ffradius ffR, ffwith
ffthe ffwire ffmaking ffa ffconstant ffangle ffB ffwith ffthe ffvertical. ffThe fftension ffin ffthe ffwire ff-
ffAnswer ffis ffgreater ffthan ffmg.
You ffare ffriding ffin ffthe ffforward ffpassenger ffseat ffof ffa ffcar ffas ffit fftravels ffalong ffa
ffstraight ffportion ffof ffhighway. ffThe ffcar ffcontinues fftraveling ffat ffa ffconstant ffspeed ffas
ffit fffollows ffa ffsharp, ffunbanked ffcurve ffto ffthe ffleft. ffYou fffeel ffthe ffdoor ffpushing ffon
ffthe ffright ffside ffof ffyour ffbody. ffWhich ffof ffthe fffollowing ffforces ffin ffthe ffhorizontal
ffdirection ffare ffacting ffon ffyou? ff- ffAnswer ff-a ffstatic fffrictional ffforce ffbetween ffyou ffand
ffthe ffseat
-a ffnormal ffforce ffof ffthe ffdoor
NOT ffa ffforce ffpushing ffyou fftoward ffthe ffdoor
The ffearth ffis ffa ffsatellite ffof ffthe ffsun. ffSuppose ffthe ffsun ffwere ffto ffshrink ffto ffhalf ffof
ffits ffpresent ffradius ffwhile ffmaintaining ffthe ffsame ffmass. ffWhat ffeffect ffwould ffthis
ffhave ffon ffthe ffradius ffr ffand ffthe ffperiod ffT ffof ffthe ffearth's fforbit ffaround ffthe ffsun? ff-
ffAnswer ffr ffand ffT ffwould ffboth ffbe ffunchanged.
The ffMoon ffdoes ffnot ffcrash ffinto ffEarth ffbecause ff- ffAnswer ffof ffits ffhigh ffspeed
fftangential ffto ffits ffpath. ffIf ffit ffslowed ffdown ffor ffstopped ffmoving ffall fftogether, ffit
ffwould, ffof ffcourse, fffall ffdirectly ffinto ffEarth. ffWith ffits ffhigh ffspeed, ffthe ffMoon ffwould
fffly ffoff ffinto ffspace ffif ffit ffweren't fffor ffgravity ffproviding ffthe ffcentripetal ffforce.
An ffelevator ffis ffbeing fflifted ffat ffa ffconstant ffspeed ffby ffa ffsteel ffcable ffattached ffto ffan
ffelectric ffmotor. ffWhich ffstatement ffis ffcorrect? ff- ffAnswer ffThe ffcable ffdoes ffpositive
ffwork ffon ffthe ffelevator, ffand ffthe ffelevator ffdoes ffnegative ffwork ffon ffthe ffcable.
A fftractor ffdriving ffat ffa ffconstant ffspeed ffpulls ffa ffsled ffloaded ffwith fffirewood. ffThere ffis
fffriction ffbetween ffthe ffsled ffand ffthe ffroad. ffThe fftotal ffwork ffdone ffon ffthe ffsled ffafter ffit
ffhas ffmoved ffa ffdistance ffd ffis ff- ffAnswer ffZero.
Assuming ffa ffcircular fforbit, ffthe ffwork ffdone ffby ffthe ffgravitational ffforce ffexerted ffon
ffthe ffEarth ffby ffthe ffSun ffduring ffa ffshort fftime ffinterval ffin ffwhich ffthe ffEarth ffmoves
ffthrough ffa ffdisplacement ffin ffits fforbital ffpath ffis ff- ffAnswer ffZero.
Two fficeboats ff(one ffof ffmass ffm, ffone ffof ffmass ff2m) ffhold ffa ffrace ffon ffa fffrictionless,
ffhorizontal, fffrozen fflake. ffBoth fficeboats ffstart ffat ffrest, ffand ffthe ffwind ffexerts ffthe
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