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PHYS211–Exam3NAME__________________________ FALL2016 Thisexamhas20multiplechoicequestionsworth5pointseach.ForeachquestionchoosetheanswerthatisMOSTcorrect. Markyouranswersonthisexamsheet&thescantron.Turninbothwhenyouarefinished. 1.Amassistiedtoastringoflength0.75-mandmovesinacircularpathontopofalevel(frictionless)tabletop. Ifthemaximumtensionofthestringis20-N,whatwillbethemaximumkineticenergyofthemassbeforethe stringbreaks? a) 7.5J d) 27J b) 15J e) Cannotbefoundwithoutmass&speedofthe c) 20J system 2.AspacestationhasacircularorbitaroundtheEarth.ThespeedofthesatelliteisV,theradiusoftheorbitisR. Whatwillbetheworkdonebygravityduringonecompleteorbit? c) mgR 1 a) mV 2 2 d) − mgR b) − 1 mV 2 2 e) ZERO 3.Aparticleexperiencesavariableforcewhichproducesanaccelerationthatisproportionaltotime.Whatwill betheresultingproportionalityforthekineticenergyoftheparticle? a) t4 1 d) b) t2 t2 c) t e) Thereisnodependenceontime Questions4-6refertothefollowinginformation: Avariableforceof F( x ) = 3x 2 − 4 x + 5 Newtonsisappliedtoamassof5-kg.Themassstartsattheoriginand displacestothepositionx=7meters. 4.Whatwillbethechangeinkineticenergyforthedisplacement? a) ZERO d) 620J b) 124J e) 1400J c) 280J 5.Whatwillbethespeedofthemassafterthedisplacement? a) ZERO d) 38.0m/s b) 10.6m/s e) 56.0m/s c) 24.8m/s 6.Whatistheaccelerationofthemassafterthedisplacement? a) ZERO d) 38.0m/s2 b) 10.6m/s2 e) 56.0m/s2 c) 24.8m/s2 7.TheweightofanobjectonMarsisone-thirdofthatonEarth.Whatwillbetheratioofkineticenergyofa massMmovingwithspeedVonMarscomparedtothatofthesamemassmovingwiththesamespeedon Earth? a) 1:9 d) 3:1 b) 1:3 e) 9:1 c) 1:1 8.Whichofthefollowingbodieshasthelargestkineticenergy? a) MassMandspeed4V d) Mass4MandspeedV b) Mass2Mandspeed3V e) Allhavethesamekineticenergy c) Mass3Mandspeed2V 9.WhichofthefollowingisNOTanexampleofenergyorwork? a) ma 1 d) mV 2 b) Pt 2 c) Fd 1 2 e) kx 2 10.Abookslidesacrossarough,leveltabletop.Frictionwillchange: a) KineticEnergyONLY d) Kinetic&ThermalEnergyONLY b) PotentialEnergyONLY e) Kinetic&PotentialEnergyONLY c) ThermalEnergyONLY 11.A20-kgcannonballisfiredatanunknownangleoverahorizontalfieldwithaninitialspeedof150m/s.When itimpactsthegroundthespeedisonly145m/s.Whatisthechangeinthermalenergyforthesystem? a) -100J d) +14750J b) +100J e) ZERO c) -14750J Questions12&13refertothefollowinginformation: Aforceof25-Nisrequiredtostretchandholdaspringadistanceof10-cmfromitsrestposition. 12.Amassof2kgisattachedtotheendofthespring.Thespringisreleased,whatwillbethespeedofthemass whenitreachestheequilibriumpositionofthespring? a) 1.12m/s d) 2.5m/s b) 1.25m/s e) ZERO c) 1.58m/s 13.Howmuchpotentialenergywillthespringhaveifitiscompressedtoadistanceof15-cmfromitsrest position? a) 2.50J d) 5.63J b) 2.81J e) 37.5J c) 3.75J 14.A1-kgmassslidesdownafrictionlesstrackfromanunknownheightand throughaloop-the-loopasshowninthefigure.Whatminimumkinetic energyisrequiredatthetopofthelooptopreventthemassfromfalling offthetrack? a) 5J d) 49.05J b) 12.26J e) Cannotbecalculated c) 24.52J 15.Anelevatormovesupwardwithaconstantvelocityof2m/s.Whichofthefollowingistrue? a) Thekineticandpotentialenergiesbothincrease b) Thekineticandpotentialenergiesbothdecrease c) Bothremainconstant d) Thekineticenergyremainsconstantbutthepotentialenergydoesnot e) Thepotentialenergyremainsconstantbutthekineticenergydoesnot. Questions16&17refertothefollowinginformation: AcrateofmassMisshovedacrossalevelfloorwithaninitialspeedof3m/s. Itcomestoahaltaftersliding2meters. 16.Whatisthecoefficientofkineticfrictionbetweenthecrateandthefloor? a) 0.07 d) 0.67 b) 0.23 e) 1.50 c) 0.46 17.Ifhalfthemassisremovedfromthecrateanditisgiventhesameinitialspeed,howfarcomparedtothe originaldisplacementwillthecrateslide? a) Itwillslide¼oftheoriginaldisplacement d) Itwillslidetwicetheoriginaldisplacement b) Itwillslide½oftheoriginaldisplacement e) Itwillslidefourtimestheoriginaldisplacement c) Itwillslidethesamedisplacement Questions18-20refertothefollowinginformation: A75-kgskierslidesdownahillofheightH=50mandmakesajump offofarampatanangleof30°withrespecttothehorizontal.The skierreachesamaxheightofhduringthejump. (Neglectfriction&airresistanceforthissystem) 18.Whatspeedwilltheskierhaveuponreachingtheramp? a) 13.8m/s d) 43.3m/s b) 31.3m/s e) 100m/s c) 38.3m/s 19.Whatwillbethespeedoftheskieratthemaxheightofthejump? a) ZERO d) 33.2m/s b) 12m/s e) 37.5m/s c) 27m/s 20.Whatisthemaxheightoftheskierduringthejump? a) ZERO d) 43.8m b) 12.5m e) 50m c) 37.4m