Exam2 Fall09 - 1. A ladder which weights 800 N is leaning...

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Unformatted text preview: 1. A ladder which weights 800 N is leaning against a wall. The length of the ladder is 5.0 m, and the center of mass of the ladder is at its center. The base of the ladder is‘3.0 m from the wall. Assuming that the wall—ladder Contact is frictionless, what is magnitude of the force of the wall on the ladder? (Note: the ladder is stationary, since there is friction at the ladder—floor contact.) D , FT N E- Tflg— (A) (vi—I6 // f d g- 7.745 e x ‘ (a)100N fl LADDFJK A13 b3 ‘2: LESQHL (b) 200N i I L 00N fl ' (d)400N UKSE 2:23:53 AHb SET T+\—E-3 (e) 500N BASE or: 7'11”; LADDER A: cjaoa 02347;”) Cn-C. {am/E? {Zak ft 0 = zen—Jed) sum 7F1L>sm~9 * TM“ ._ _ 800 3 _ 33 M . if a. 5 me- " 7- 46‘ . . . . 2. A tuning fork produces sound waves of velength A in air. This sound 18 used to cause resonance in an air column in a pipe, which is closed at one end. The length of the pipe ' Yl :i CANNOTbe: FOR A. oven} AT (MOE END, ‘ (a) V4, ’ I i gfl—' "(MVH'92A/4 L 2 25!); wHERE n 1-: 7m; Moog Mum»ng la '—' c) n ‘1 i591) i’n I' T 3/4 ( 3 l 5 (SEE bfAéZ/mrzr (.2157) f (d) 5A/4 ’ ’ g m 56 Ré’jarJ/CMCES accuR AT Obb'Mumgd/ZED <6) W4 eowm Mew 9”” - r -3 A) w 5.. ...._. ~ - .4; .2: (flyogmgwma mam?) " ' 1? _, i be “7‘3 . n-l if a (1% )5 {34113130 9‘ I 3— "4 Q h '— 4 F4) 32'? 4 % 3. A massive disk with rotational inertia I = 20 kg-m2 is initially not rotating, but then a ch _ constant torque 'r = 2.0 N -In is applied continuously for 10 3. What is the magintude of the angular velocity of the disk at the end of the 10 s? W ( ) 05 ad/ Pr??LI<—SD TN? 6906 fmfixf/ZN Wflfl/éé/Lflr? AzaeugR/N’ a . r s i _ .3; (b) 57rrad/s C7;ng g/JJFHJR :: 0‘ ‘ L @lflrad/s 5° ‘7‘ 7‘ E : -/ 5 (d) 5.0 rad/s To 65:7” jflgr/LA'I? yflocjry a.) use’ (e) noneofthese we.) 3 D90 +w<+l @Egrflr Film £6,579?) pa :0) who) :Qilha) : /5" A 4. A playground merry-go—around has a radius R and a rotational inertia I. The merry-go- around is spinning with angular velocity we and a child of mass m is standing at the rim a distance R from the center (i.e., from the axis of rotation). When the child moves to the center, the angular velocity of the merry-go—around is: Us safe, cm 54am mflonf 0F Awe own? WWW/7”": (a) we ,1. n A. U. @wo(1+mR2)/I La “Lfl —--> :J}M%.‘>w4 1 Jae, (C) wo/(I—mRZ) : I+MX2 If : I (d) wo/(I+mR2) 5, (Iflmzz) we (e) mR2wo/(I+mR2) w; r "7:"— wygrze 3: I?! 77/5 295.1”:ng 5;: fizz/97;» c3x: rive” 2474278271—676 f/ZJé/fl/D f and 1:: a)- I 5. A top spinning on the floor precesses because the torque due to gravity, about the point of contact of the top with the floor, causes the angular momentum of the top to change. The direction of this torque is:: E3 H . BL, b Eprfljfldfl/OF (a) parallel to the angular momentum 7%; C R a, {)5 7LoDuo'i" ..—L I (b) parallel to the angular velocity vector """ —t q A 7: J. r" , “t .L F (c) parallel to the axis of rotation A __,__ ' . r - 5 MW“ 7/“ (d) perpendicular to the floor “13 ' F FM 77"}! fr, P J ? 111,120" A a none of the above ‘— W91 V656 Tm Tfiir J’s 611 e . To rhpjgwfldflngTMf (' a SchJFféZD >3/?€¢71:""‘J5~ Tflf/f 7M 4M: #573? :25 fflflflééé’é To 7 6. A pulley (which can be considered to be a solid uniform cylinder) with mass M z: 40 kg [7 ('90,? ' is susPended from the ceiling. A rope passes over it with a 20.0 kg block attached to one end and a 10.0 kg block attached to the other. The rope does not slip on the pulley. When the speed of the heavier block is 2.0 m/s, what is the total kinetic energy of the pulley and blocks? (Hint: The radius of the pulley is not specified because it is not needed. For the pulley, K = éIwz; both I and w depend on the radius R of the pulley in suchaway that it cancels out.) I 3’- imgz' A”); (b ;§'£ 5° Idlgflimgl) L V . J 13* (a) 40 J ____ I 1’,” V 9°”? 7W” ALL. t/EWC 7' r (b) 603 I 3:“ A‘ka w:— c 1 2' .1 z I 100.] 0 k-zf’jl/ f2M,_lr 4"2' 15...)?" p ,z , - 1v (lo-Ho f 10) I p A :65 ll \ a a 7. A planet has twice the mass of the Earth, and its radius is twice the radius of the Earth. Approximately what will be the acceleration of a massive body dropped near the surface . 7 , r_ ofthisplanet. Fag dale fl/g'm [Divan/gt: m _2M th:2/? r (c)20m/32 Sgfiéf’i H GUM) 5257’” / _ a, are: R * w 3°13 w e HIS 8. An object is dropped from an altitude of three Earth radii above Earth’s surface. If M is the mass of Earth and R is its radius, what is the Speed of the object just before it hits Earth? (Hint: Assume the Earth is a sphere. Notice that the object’s altitude measured fi-om the Earth’s surface is not the same as its distance from the center of the Earth-) WSINfi gwsgamrrw/Im‘ Ext/54577! cwkzr; Lg (Mayan): (a) MGM/R START FROM 4 R (METH5 KAPJWJ 4- 3mm: ABMESVQFACE w’STHRT [2% I“)? «56 :5 D .. : . (b) MGM/2R ‘° M F Ula M A“ M :5— - M - c - mm (C) x/ZGM/R kAa — 1% 5,5 HAUL, ..(%ng..% __ M 74,; @«flGM/ZR 5 39M ' L L 36M 5 m (e) 1/4GM/3R ° —# k :imv _ —> 570 : Jyflf‘ \/ t q/ 3% I 9. At the same instant that a 1.0 kg ball is dropped from 40 m above Earth, a second ball with a mass of 2.0 kg is thrown straight upward from Earth’s surface with an initial speed of 10 m/s. They move along nearby lines and may pass each other Without colliding. At the end of 1.0 s, the height above Earth’s surface of the center of mass of the two-ball system is about (in your calculations use 9 = 10 111/52): (3352111 7746’ Cam fiszmfl I5 taxman/£7 KW” :Jég‘lm‘t; (b) 10m new??? 1’2 70:: H1) (d@:5.0m l“. ‘bpfivfi ~13: AND la}. =L°1+v1+ -35 f1 ((6; 33: lm 3* 49 +0 ~ijf = ‘2’0"1{/a)(r)" : 4/0 -5; 35" $0 "1“, = (/)(35’) :36' “1: 0 +047" “éljfz I CNN/l diff/002) V” “’35— 56 mill;— : (“Ma 5/0 5" £12m” = (5.51791 =45" .L #95 Maggi“. 2" dun/f) : 6f 10. 11. 12. BAWN‘E’Jl We, 54!? 28’?u.r2€$ 77/17'7' WWW; “*6 2.3/30- 2347;» Film} + hilt— Mjl dig) 31? A ball of mass m = 0.2 kg travels horizontally with a speed of 5.0 m/s and collides elastically with a wall and bounces back with the same speed. If the collision with the wall lasted for 0.04 s, the magnitude of the average force exerted on the ball in this collision is: ...._E'__._> T) :m‘j‘ 65- :—/ (a) m 6‘73; " ‘ 53*:th HAWK) :+/ Fiipzflp’tép' : (—0!) :35 :fonf (d)100N 53" + "’7 "’9’ (e) 12ON A person of mass m == 100 kg is standing on a cart with mass M = 400 kg which initially moves with speed 10 m/s on a straight track. At some moment, the person starts running with speed 5.0 m/s with respect to the cart’s floor towards the back of the cart (i.e., in the direction opposite to the original motion). What is approximately the speed of the cart now? (Hint: remember that the person’s speed is measured with respect to the cart after he starts running.) urn/S «Ann/«5 ém’feflm‘rw “5 MdMWT'V’”, (b) 9.0 m/s Mg: #4:er (Pf. I (C) 7-0m/S CENWR~0F~WJS "Lamar-170’?“ I" 6’Z/Wg7 : (d) :0 111/8 50 E; 1‘ (Mtyl e‘mlva :[t/dolCéb) Z/JM “Viv €153,610 e 0 s ' 3 0 1:. ya () 111/ so raga :Qgpv, #11 film” : igloo) vqff‘o 4(09'449V 5‘, v: £70 :75// A block of mass M = 50 kg rests at the end of a rigid uniform bar of length L and mass M = 50 kg. If the bar is supported at the point L/4 from the block, What force I3 is needed to hold the bar horizontal if it is applied at the other end of the bar? (Hint: the mass of the uniform bar should not be ignored. Take g = 10 m/sz.) (a) 0 N [E] if: (b) 10N 4 (c) 20 N riff/W 1E (d) 30N m (e) 40N 3 M1 dd, 7%? P Tiff JuPPdRT as 77/15” Mitt/7M2 ‘3'.— (Cipw :0 so Eel—X4] :@)(Mj){—;)(mjg : e. 5577:”)? 13:9 mac 55M» 0/ r ) EAL/secs») $1: W a uscgssM. p,er a» (stem, so w PM 1.1. was sjsrsmfi‘é Ari-Ritz; £5 13. A 400 N weight is hung from two ropes as shown. The tension in the horizontal rope “15.7.— has approximately the magnitude of: PM! STATIC. E? I V [{QTI CA L P54 (v (‘5 m BA’L-r‘t/‘JOE; AS Muff #okra—aflrflt— . ~ I (b) 400N ( i “P (c) 920N """ " ‘4" w "-7371 (d) 1150N was (6) 540 N Honizontalmpe A Z‘ Fv :0 fig 11? 2 40012:; Twp SM :- fllfigo 2% 313.120 “Tint? “5°10” 2!? #97: 800“ it”! -. A — ._ ‘ ,— - f 1:. 47/ we ’ swam 672 , 7; :7; s. xii/7:23;“ new“ 14. The displacement of a 7rsritring carrying a sinusoidal traveling wave is given bx A’ y(:r,t) = (1.0 cm) cos[(§m_l)x —— (5.0 s—l)t]. [4 c'r'e’ 714/47- 75? DyspL/CWF What is the Speed ofthis wave? purge-rpny j; 70".” : A (as {k X -uH.) I “ "IT ((3 ggl/S/ 5° #32:» a 4am 5—: a; . 7r m S V 63— VL‘ 3 f ; ‘ “Cf—o @10/17 m/s 1 k ‘ ‘50 V ((717 i 77— (d) 1.0/7r m/s (e) 5.0/71' 111/3 15. An object of mass m = 4.0 kg, oscillating on the end of a spring with spring constant k m 64 N/m, has amplitude A = 1.0 In. Its maximum speed is about: (a) lZm/S Kw) : A COS 0.2+) mob \JC—f) ~— g; mm $349+) (b) 10 m/s MMImum SPEED 325 7W5 GEE/50¢ aye/if n5mm+):+g :_ I 7.0m/s MD V‘ 3 “A . (A) ‘ i 4.0 m/s $6 (elm/S V‘— smh/Elm/ffla = M: 16. A moving source emits sound with a frequency of 500 Hz. It is moving toward a sta— tionary observer with a speed of 170 m/s. If the Speed of sound is 340 m/s, the observer hears somid with a frequency of about: 1000Hz WK 7’49, €?'//"7J“"/ PM :4 “MIA/9 fat/flee? (b) 800Hz f gaf; 71%; 5wch ;5 Marga/9 days??? To ‘F I , ,7}? 4 IL ) 750 Hz ' so 7 A; 7% Dé/p/dW/Vf (‘3 fair as we Mag 75 if fl 9 (d) 500 Hz , ,(P fig Mwuj 554M ,fp/fi <36”. (e) 3001-12 50] wt, flke’k 2 1‘ 5‘00 £5 . 5720 f U12: r #420: va—f’ ~ “f ,«zow 7 . 3? 2— ...
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This note was uploaded on 12/02/2009 for the course PHY 317k taught by Professor Kopp during the Spring '07 term at University of Texas at Austin.

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Exam2 Fall09 - 1. A ladder which weights 800 N is leaning...

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