Physics_8A_-_Fall_2002_-_Jacobsen_-_Midterm_2

Physics_8A_-_Fall_2002_-_Jacobsen_-_Midterm_2 - University...

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Unformatted text preview: University of California Department of Pi r” Physics 3A. Fall Second Midterm Exam November ti. 1on2 You will be givett lfl-[l minutes to work this exam. No books. but you may use a handLvrilten note sheet no larger titan an 3 NE by 1 l sheet of paper. Your description of the physics involved in a problem is worth significantly more than any numerical answer. Show all work. and take particular care to explain what you one doing. Write your answers directly on the exam. and if you have to use the back of a sheet make sure to put a note on the front. Do not use a blue book or scratch paper. sin 45" = Ufifl't. cos 45” = {Hill sin 3G“ 2 ilfiilil. cos 3D“ = flfififi Rotational Lnertias for radius [it or length L: - sphere about axis: {EISJMRE spherical shell about axis: IEEt'B'tlfle2 disk about axis: [lt’ElMRg hoop about aais; MR2 rod about perpendicular at midpoint: i"t.=lL::'-tr 12 1PV2+V9fl+P=CGfl5tElht i-'-=Emu“2 tn=1i£ m=J-g: Ef=ma 2 t"2 m 1' Each part is worth the number of points indicated. These should sum to lilil points. Setup and explanation are worth almost ail the of the points. Clearly state what you are doing and why. In particular. make sure d'tat you explain what principles and conservation rules you are applying. and how they relate. Fri ntseusSIoN SECtiDN Daren'tsia: Read the problems carefully. Try to do all the problems. if you get stuck. go on to the next problem. Don't give up! Try to remain relaxed and work steadily. 1A] {2 pts} A ladder leans against a wall. If the ladder is net te slip, which ene pi" the fellnwingtnust he true?r a} the coefficient at friction between the ladder and the wall must net be new - Blithe cctefficient of friction between the ladder and the finer must net he zere e} hath a and h - d} either a er I) el neither a ner h 13) (2 pls} if a sphere is pivoted aheut an axis that is tattgcnl as its surface, its rotational inertia is all us MR1 1': bi 35 MR3 _. -. - y 9 in tea2 ' .-;’_'§»t Te MR1 ' ' "-'~' e} are MR3 3- w 10} [2 pts} We may apply eenseryarien ef energy In a cylinder rolling dewu an incline witheut slipping. thus saying no work is denc hy frictien. because a) there is up frietien present h} the angular selecin ef die center ef mass aheut die peint ef cuntaet is zero e} the eeeffieieut of kinetic frictieu is acre --d_} the linear velocity ef the peint el" centact {relative tn the surface} is acre let the ceeffieients of static and kinetic friction are equal in this case 1m {2 pts} A figure skater stands en nne spet en die ice [assumed frictienlcss} and spins areuud 1with her arms extended. 1|ill-"hen she pulls tn her arms. she reduces her retatienal inertia and her angular speed increases so fliat her angular mementurn is eensewed. Cemparecl te her initial retatienal kinetic energy, her retatienal kinetic energy after she has pulled in her arms must be _r - I ' s v.2" ._.a} fire same. I _ h} larger because she's retating faster. ' cl smaller because her retatinnal inertia is smaller. 1E} {2 pts} in simple harmonic metinn, the magnitude ef the acceleratien is greatest when the " — " — ' a} yeleeity is maximum h} displacement is acre e) ferce is acre d} displacement is maximum e} nene ef these .._1 -I-.J.-J.1'.-.t. 1,; F..1-_.J J :1 W 3:“ gill-u J pt “I: I'LL? I] F . d x - ~"'L"“'-_" U 4* Paar-“1"? v.1 1H ll r. t' ._-I a» ,-...| In. if fr“ .4 El 23' . kl 1L; I.” kiwi”! 3*: “Music. is Li-E-r'rv'll bw..';.-1" await-LEM 5A. " I I L '.._,...I' E— 1" -4" fl'v “ti luff-{LIE’tc-f 1I. lacs-mi. [Gm-t t i :\t. ._-_.._f‘_ iba U ' — . I Lulu-“Etii 'Mi‘A-J' \m - l_ _ ._.F‘j II I I . . .r ' . I —:'.' 4:... .‘I m Thin |_‘I .1 __' It: II- I I. I w “r J” ‘5‘ "”""""+ rested mm “in s y‘ ..-.....r Ir.“ .1s...ssfi.i..c.i '. ' ' ._..I ._. I 2A] (5 points} Water is flowing from a reservoir. The tube varies in height. At which of the daree points labeled A, B and C is the fluid moving fastest when you ignore frictional loses, viscosity. etc? At which of the three points labeled A, B. C is the fluid moving fastest if you include the effects of friction on the fluid? As always. explain your answers. tam-mull! 5 ~Mi‘l3rv E PF. -1' {E III" U?- _.+ Eh'ilk F (-‘L. .- — . r .-| 'u'iuw 'm -: “Ln.- .- I-hrIEJ'II'j'i carer'vrhvr “£- Eycwtb.e--A$:I"a u: but” L2. in flu-t ctr—v It?” ' F J ‘1'" . III . . U . - ‘ L-I . It: " -. . _ I _. h, - -‘ a I_.' I- r_fl_"- Iggy-"grailtrsl “Uni? fiat-HIKE; :Iffi “AA-{DT‘B I. LL-J I“ Jilin 1"". T. lr‘l Ii PM!- [L -|'L f if f |'_ 1] ..-!}_n__:.-".n -|;[A_I (tn-T J I_,‘_L_l._',- L Mn {:23 I,.F...I{uf\,...,_l: {j'EI(_-'r‘ I‘lfl-‘in’fi-fi . - ct 23} (5 points} Water fills an oddly-shaped cup {see figure}. ls the total force exerted on the bottom of the cup by the water greater than. equal to, or less than the weight of me water? As always. explain your answer. - r" I II I“! '1'I-u JL‘E-tu_|'_.~f'c we; .a W $qu |-:- —- :1..- lm-TFN'W'A wal‘éflfi . . | .' - —- . . .. ,.J .- ra'. ".L'. :'I.I_I:- La MFA-A fi'n'" V’t'lw' - I H'- ‘I' - .1' fl 'I'l I ' 'I i‘" am; haul-it: EWIij u tin-Ln .II-f_._- Half} Lril at rt |._-F[._ {gnu i,- _{, c In, lrJ." Tim IfliII-LI‘JLFJ Ear LII-l: I !' :- leg-Ed,“ III“. ref |'_.1 Cf 'I'ithd 'RH'J'I‘PLT-fl'r Pbljfi.‘ P I! In 1"“ LIL-'1' {5’1 .3 | | I"- ..: a“; .',.. 1. I: LL}! Iii-r- ,J-tr.a;i—.ra.r-4.>L.» synH'H- .5. L, .c LcFINHtht/v fl ._. ., 1. 1_ I_, If I. :I _ . | l' I._.:l {1 LI"- . - _.-. .- . -. [if I“. “1;... W: “I III-re... | lymw‘fihl: 313p. :ql. Lid-1 ‘l|_ I“. .. l. I [In Jun + u DIM- \ r A III T J D! If _ I uJ QM Fr! to |’ “Mi-3'. L'V1"'J “ I “._.-G 4.5.; .411 TEL L] ’I I: I-EIL’ E 'LFZI'IL' TV“. I “t. Ila-'7 5|; '-{|.‘ut ova—4ft yll'j. AWL- [twig-“91W? IP-Li' r .. ._- l 3 {2G pts} A reel of length L and mass m is attaeheel to a wall with a hinge at ene end. The eenter ef mass ef the red is in the eeuter. The red is released frem a horizontal penitien. a} At the memth ef it‘e release, what‘s it‘s angular aeeeleratien a. aheut the hinge? b} At the moment of it's releaSe, what‘s the dewa'tward aeeeleraljen a of the center ef mass? 4-.' T' L ‘i' lull-3L rh-H—n.‘ L '12.? _ r, -_--:.T]_— f. 3,! .- F_ t . . T M L J 'W'N'. :I %: _ ' I..1. l I —-‘—F H ' | f 51‘ n' '1_ ‘r ' I I' II .r_'.' I»? .. r'"I‘I "’L‘ "‘"l _ J I . .-. - -_ '. - '. ' " '-" ' - '-l - an ~~ u -~ ‘— r :~_ I . -'— ml ll.._._|.:|' N‘J' l ,_|.L ~ <. PM _ H. J7 Illin- __.J_ -. _ .. _f— _t ' -r _———I ._ I IL 4 1—4 r. I.“ch . Li .. - r {fluff-a 3 _"_:‘L " _— __.—.o——_ f ' I: lJ' a I L! .:| . '1‘.-'I _: ' ' " If" 5' a—L'Jr -.'- ’1 I. .l_.1_; 4 {2G pts} A lllflfl kg car is bai =lU cm, and the small density as water. See figure. a) ‘M-IaI is the pressure a: point A? b} What is the measure an point B? rug lifted by a hydraulic jack. The large pismn has radius piston has radius r=l cm. Hydraulic fluid has abdui the 5am: 03:91 1 9 “I J. I‘. ." r H r {JET-L Jr J'r-EI r1'. I-I :AIJ."'"__.I J ' . "fl-L. fl. '1::‘.=_.4|-..".J Lid-r I: :IJIJ- ll.l.ll.|_.: I. I Hi: I_\__ I r .I' ‘i' I l r 1/: ||'_ I' _ : I, L— .d" _. | -'F ll 1 :5: m T. l 'r -_ I. I _-. 1. W25- .r' _ _ :‘L Fin _ Pu I. M. .J' [1.1 .1 -. ': _I h, ' -.-- . : I L _ |-.J : r - _1: r- r. h " - l M p‘ . a - |-_-" .- J _dl I F II‘::' II I = If .I2I_ 1. ‘llia . . x _ I'i.-|_-_‘-_,i H r. r _ [Lilli ] . _- -r . a” 5’ _ I I - _ ...7.__}I_.II ..— .i}-:- ll __ It... a”. . I.- _ l-: ‘ -— —-ll I' 'I ' | r _ _ I IJ 'l'. ra- ’ 1'“; Han. - — '- III; .J 1" f. ' .7! 3!? -' Tl' IL"— .—- _.r“ 5 [EU pm} A whael of radius r and 1113.95 111 would normaitfi [fl1_1_dnwn a ramp. In This problem it’s CDDSLE‘Hjflfid by :1 string. which pmvants 51 {Toni—rillling. What's the tension in HIE string? 4' a "an. E ’0 "q j} P I f '1' x _ \H LF r w T Era-K - Jujl .T _: __ . ,1 f _ I _ Ril- r.- ‘. :_l '_-5 "a 'a ("I Jirjw IE-"H'u‘J-‘l. L'l' .3. -_ ' -r' H."*E~F\\:J_) a. — __ . -‘ . "5",' T' '5 T'r I“ *- T r " '--' F rum 5 ] .l i:.'_ , A . — :Jr r"~ 5‘. ELM-'3 " ', r' — _ _ _r L I; '- T — r-Ml‘fr-=-b"l .l J (—1 2T - my»; -._J _ I II ’ '3 r: - ' __'...'. __ I xl u:‘:: _ ‘1 "II “L. ' I -" E l-_. C3. 9 I l I'l'f'a' 6 (2H pts} A block of mass rn is attached to a spring with spring eo slant k. The mass is sitting at the equilibrium position when it is suddenlyr _h_it_ to add e rgy E to it. it then oscillates around the equiiibrium position with opened}. ‘ "1:: a} What are die maximum 1mines of the position. velocity and acceleration of this motion? in} Make it sketch showing where in Ihe motion those maxima occur. {Eg at the center. NE of the way through, or whatever] is- E. ‘-= 'Ifi-E = swan: -F- .—|-. —r I . l _ —| '- L‘ LEI _: F'Jcl- .IITMLH _ F- F; I'.-. _— ' .n .. . . . PJ I: v (If. all Ii-rb1'."l{ LL" I'I:'.'I {Ii III-{Pr} .‘v- {II-'b'll’Il-I “4”- :- I] -' If. ' 'f. L '1” : +e-—:--' " I: i v i i..." ' 1-H“- I "| I I. I I II.I IZI -_ I '- 2'. r - -"" II "" r ' '3 r':.: ’1'. fi'lt:_ xhfl‘r *I'fv I J L .r- " [er ~- —TF_' .I -" Mar I" Lv' _ J I: j“ “x ' '- th [5—7. _ _ I ._.- ir'I- L w . uL-c-‘r T " L u"""1 "a? if ‘ FEE—I 4 -~ _ . I .2——‘| -'-'.-| -+:_ .' '-'__ _ -'- ‘___T_ir_1___ . v in K “ILA—V“. ail ‘- V I): I if L" .——| _.—.— 1 -' -1 | 1 _ J- 'LE : ' " I" Lt . _ J r I — I - '- w: | V" Xf-fl'! '1' r’. _I__' I I .LC II .—_—| _ '.z . '3—: l—'— r 'l'r': W 'i. . -<-'IT - IIITIIJ _'\u|'r,u. r. H .' __ J V. I: r : I _ - I I I | — r— i -" 1' _. .II I ___ .|-— . r -31. I ...
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Physics_8A_-_Fall_2002_-_Jacobsen_-_Midterm_2 - University...

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