sample_mt1_soln - LPG/U 7/22»: 7‘? Sample Midterm Exam #...

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Unformatted text preview: LPG/U 7/22»: 7‘? Sample Midterm Exam # 1 Physics 8A, Spring 2011 (Section 1) Name: Student 1]): Discussion Section: Name of Teaching Assistant: This examination has two parts. Part 1 consists of 11 multiple choice questions worth 4 points each. You need not show your work here. No partial credit will be given for these questions. There is no penalty for wrong answers. Part 11 consists of 3 problems. These problems each have multiple parts. You MUST show your work for these questions. All work must be done in this booklet. No blue books will be accepted. If you need additional paper for working the problems on this exam, raise your hand and the proctor will bring you paper. Make sure any additional sheets are stapled to the exam [the proctor will have a stapler). Calculators are NOT permitted; the arithmetic is designed to be easy. You may take ONE sheet of 8% x 11 inch paper with equations into this exam (for the first exam, please use only one side of the paper]. Please refer to the fact sheet that has been distributed for information such as the sin and cos of angles. Perfect Score Score PART 1 PART I 1 Part I: (44 points) Answer ALL the questions by Writing the letter cor- responding to the best answer next to the question. There is no penalty for wrong answers. ' ‘ a 1. The following position vs time graph represents the motion of a toy car. When does the car have “zero” velocity? V—‘O‘Weflrnf §%:a (zeros/off (a) 155 only (b) 731 (C) '53 (d) t; and t4 only (e) t2, t4, and t5 0‘ 2. Using the same graph as question 1, at which point does the car have “zero” acceleration? 00/ d 3X a = 0 mean: .: ; 0 (a) is only (and Eur/$96.: ‘ W a?“ (13) t1 fi ) Amt or 79%“ q'fMA/E‘A’ 7‘58 5/572 (0) t3 Mina/51a” admin 47‘ .__- 2‘6 5" 7“”«76?J 7%.} refur'ummf, If 2‘3 fir Cons/Were! W7 I mf/ecfforL/paaif) qfé) A}. a/fa {hera- d e 3. Which of the following is 3 NOT a unit of acceleration? J 4. consider the vectors A. = 3i+23dand B" : i—j‘. Which of the following best represents the vector (7 2: A — E? ‘3 ‘jk - — ‘ - \Q ‘ .Ql % ~ 'I ( 3 D 2 x E ‘1‘ E? y ‘5 ‘ Ut' -.._\ .4, A A A _ A A‘B *6”7)I*(2'(’U)J Q/ : ZIP-('3‘? "2, 3 _' - 5‘ 1‘ 5. A prince is being held captive in a tower which stands 180 m above the ground. He wraps a distress message around a rock and hurls it straight down with an initial speed of 25 m/s. After how long does the message hit the ground? (C: :8 {NL ‘15]? fora/“Ive y d/‘rliecffan ée. a/Ownward_ s _ 2 ' ,__ 4/- 6/47 +3!ij (a), 67/03) (9)7.23 [‘90 :Zfd’ff'fdte [fa/am/r‘é) 3%2+fef'3v/:P' 47": “fluff (s) / (7m); fJ/IJ'I‘CHI ‘" fir} nick/d 32 52/404 7%; 7%” 5 6. A block of mass 10 kg slides down an inclined plane as shown below. if the plane makes an angle of 37° with the horizontal and the coefficient of kinetic friction between the block and the plane is 0.1, what is the magnitude of the frictional force? ' (a) 5.88 N 5/ d} (b) 7.84 N \ l (c) 9.80 N .3” ((1) zero °\ (e) 98.0 N Wm} ‘31“ a 7. A block of mass 10 kg is attached to a spring with spring constanj : 2 84¢ ) k 2 10 N/m. The spring is stretched 10 em and let go. What is th . . ? maxnmun velomty thjljilihas. m t [0 k2 ’ d: at (I M (a .1 m/s ‘ I I E ’E . (b Jim/s n 1 A lit/4”” “(537763 .33m/s :47, => v=gd=-£LE-o-I=a-lf%/ (e 10 m / s l 730 (wa’fuml /e/2 274) e 8. A steel ball of weight W is supported b two strings as shown. Which one of the following relations must hold? ) l t (o) 1/x/im/s lggggglfl' B 7 0 * 35M "jmlzwt o l l (a) T1—T2:2 (b)Tlsin9:W (o) T1:Wcos9 .9“ (d)TE+T9:W - (e) Tlsin6:T2 v, t i: V a 0-9—9. 'lw ‘t’ Tats/mo 4 ; 73th@ :72 (nape Coffé'cf) 9. A skier of mass 60 kg goes down a slope as shown. If she starts from rest at the top of the hill, what is her Speed at the bottom of the hill. You may assume there is no friction 91¢ (a) 15.6 m/s K + M; : [{f 1 ’ (b) 31.3 m/s d _h l 2 500 m 3 +217 ‘ —34l'l/ + O (c) 22 1 m/s 2 _ m/S =9 )‘c MV—"F'aPé/ffa/ryd‘ef (e) 980 m/s :- Z{30 59ft: ' $329500: 797/2 237.64%) .10. A mass is moving Clockwise at constant speed in a circle of radius 10 cm as shown. At t : 0 the velocity is 1} m/s. The acceleration at t: 0 is: 2 l/ f A a 0 I —,'_' : ___—- : (a) 18 m/szi A l ( ) R 0‘ 70 A W”) - . a; , (b) —10 Ill/522' = A W 2". J S —| w A ((2)1Dm/sj 51-1/0 /5.2{ (d) —10 m/s? l (e 5 III/82;: + Sm/szj 11. A mass of 5 kg feels a force F = (4 3 + 3 N. What is the magnitude of the acceleration the mass feels? (worn/s2 J. -‘F’ , A} (bum/s2 (“Ills/"l 'Lm‘: 5 : 7 (c) 25 m/s2 (d) 5 1111/82 (e) 1/5m/s2 Part II ‘ You must show the reasoning for your aHSWers. Do this as clearly as possible so that you may be given partial credit if your approach is correct but your numerical answer is wrong. (Note: A neat easy-toread answer is much more likely to gain you partial credit than one we can’t decipher?) 1‘ (15 points) Note: To make the math easier, you may make the approx- - imation g m. 10 m/s. A boy throws a rock (mass : 2 kg) out a window. The Window is 20 3n above the ground and the rock has an initial Velocity: + r7:(5§+2§)m/s' ) 7‘ i “7+ (3.) How long does it take for the rock to hit the ground? Jnu/a/nwe if Take: ‘fz‘ma affair Me rock #0 ,4/‘7‘7legroumfl 75M} 4/: yp/u‘ -EL at; ‘20 =7 de‘j'zmdz‘a 54?)“242‘ —Zo:a 1 _ ,1 ' ' A ‘75(<jj¥4o¢)"5{7+f/o7)t5J ~3.g;(5) (fluke! fig”)! flrbeJ Ann-yofl/Jr'ca/a/pfwer) ‘ (b) HOW far does the rock travel horizontally in that time? (“r/0! )(M) ’“//+05 (2») f _ 453/: Vows; _— 5.§(/+W}; 7 (Q) What is the final Speed of the rock? n:- vmr 5 V}: :4), “£4; 1' Z-ro-§()+1/101) (d) How much work has been done by thé force of gravity during the rock’s total flight? - @rafivyferforw Work Mink, = ( 0) 4mg?) fax/14);) \. ' . : —b,;4/ ‘ (we ex/ecf’fifi 7519‘ / orr‘fv’ve. ma #9 ably/needy”? (a! a com/Men?‘ r9? 7%; Jung c/r‘recr’vbh 4.1 J M V}? ) L 2o :9; 2. (16 points) Masses m1 = 4 kg and m2 :flkg are connected by a massless string that passes over a frictionless pully. ml is held at rest on the floor and m2 is held on a fixed incline of 6 : 45° At time t = 0 the masses are released from rest and start to slide. Mass 7712 slides 1.00 In down the incline in 4.0 s. (a) Draw a free—body diagram for each mass (b) Determine the acceleration of each mass A72: 7.001451): 4f=¢0(s) 4 2 =W+ 5-621er é]: éazx‘¢a::> 427:2}- MJz) litlélsmv Mays /laCre/em7‘e.r ¢u4,‘{_a7‘2§- 7T2 Maw Z acre/emf“ q’owmrd era/on; 7%6 I>7CA>2€ a7 c—PL MA‘EA n J (c) What is the corefiicient of kinetic frictien between 7112 and the incline? ' Zf,f=7nqj/-$ T,-~m,j;?fi,éy r——(() Eli/:0 7‘ :9; A/: majearlfl' Z’iwme => We? 2;. 72 = ('2)- 14/?” fk:/Ikfl/’flkmajcorfl) 7; : 7:2 ) aha/.3549, =‘h;t(= ("A‘Ul 97M. (f)-r(2) g 7,, 223’»! 1b 'mz} 'flkMZ;Cafy=(27/+m2) Q é fl}: = We [mpawzm‘nflhmdé$0,735qu) r I f [0.01/5 4/.)0/0 inloofi r (d) What Is the tensmn 1n the stung? ‘ From e7». (1)) 7, = m7 +mflr/ = n, (g ml) 3. (15 points) A pogo stick can be thought. of as a stick with a Spring at theend. (yjeg:/0 h/rz Acre) (3) Suppose the pogo stic is standing vertically. When a boy (mass: .30 kg) climbs on the stick, the Spring compresses 1.0 cm. What is the spring constant k for the pogo stick? ":lFlzzde-Ioo-r I? )4/1. a‘o/M-_§:7-23X/o¢ (b) The boy gets off the stiCk and this time junnps on. His initial , velocity when his feet hit the stick is '27 = —10j m/s. How far will the pogo stick compress? [ef- f1: gmyrhfr‘aha/ [Do/LenT/Ez/cm/i/ 'o/dfq/g fie an s7” Wie‘mmwhf i/‘f/a?‘ in?" 7/; ,0va fff‘flk Z5? >916 May/Mk com/fernbn Xe //J’J cum/>7 M Meczah‘ca/ezyey/ {kw/$471606 ‘ (from) (Via?) __ + guy.) ' “7,”? ) K; +Z/a' ‘fé- " “eyeimyfi 0 + o I Q .l. "N I N? 5k x. 4,. g. >5 5" N (doo’ZL Olga)“L I 10 :gfiz #15 fer»: ” firth; -3, 4’ I0 L f ’74 ‘ I ' ‘: 72,—," 7 if 1/ / +1000 ) h ‘ ' — {' ' (Ia/27%»: “’75—; (1"‘1/1001) (9") Wham avg”. 15' ‘V 0-5250») - WM/‘fi‘k’h’ (c) After the Spring is compressed in part (b), it begins to expand again, pushing the boy upward. If the pogo stick transfers all Of its energy to the boy, how high will he go in the air? Z5? fl A; '7ch 5:7} War/mm 1(7/7 «Joy! 7%,: Hash) /£Ve/ of gmm‘fnflonp/ f070=fi75:¢/ dacrzlea/ I)? 7%: I'D/((qu 7‘1, f4rf’(5). - I - Com/gqraf ‘77,! meelam‘cn/ £69?% 474 #14 772,43 [Ar/’07.”! f/kfl‘ if?" 7‘19 1779} “(Fifi fie Met/ann're/ can??? Iwarxr'mwv 19:71?) w: 24.1% / I ' A?) + $023me ‘(Vr/y] :7 + r (’rufi) -/ z + a, I -- hi} + *ny +-O +' a i 0 : 0 +0. v? Ari/2i M h- .2; e\(? ' :' J alga“? 4/? 3111;), W 11 ...
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sample_mt1_soln - LPG/U 7/22»: 7‘? Sample Midterm Exam #...

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