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Physics Fall 2008 Common Hour Exam 2 Solutions

Physics Fall 2008 Common Hour Exam 2 Solutions - 10 Physics...

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Unformatted text preview: 10. Physics 123 - Analytical Physics SECOND COMMON HOUR EXAM Monday, November 10, 2008 Professor RA. Bartynski W => (pl.u Your name sticker with exam code. SIGN HERE: The exam will last from 9:40 — 11:00 pm. Use a #2 pencil to make entries on the answer sheet. Enter the following ID information now, before the exam starts. In the section labeled NAME (Last, First, MI.) enter your last name, then fill in the empty circle for a blank, then enter your first name, another blank, and finally your middle initial. Under STUDENT # enter your 9—digit RUID Number. Enter 123 under COURSE, and your section number (see label above) under SEC. Under CODE enter the exam code given above. During the exam, you may use pencils, a calculator, and one 8.5 x 11 inch sheet (both sides) with formulas and notes. There are 15 multiple-choice questions on the exam. For each question, mark only one answer on the answer sheet. There is no deduction of points for an incorrect answer, so even if you cannot work out the answer to a question, you should make an educated guess. At the end of the exam, hand in the answer sheet and the cover page. Retain this question paper for future reference and study. When you are asked to open the exam, make sure that your copy contains all 15 questions. Raise your hand if this is not the case, and a proctor will help you. Also raise your hand during the exam if you have a question. Please SIGN the cover sheet under your name sticker and have your student ID ready to show to the proctor during the exam. If needed, the acceleration due to gravity on earth may be take as g = 9.81 2 m/s . 1. An empty beer mug slides off a bar 086 111 high and strikes the floor 14 111 from the base. With what speed did the mug leave the counter? w are we b) 1.86111/s m c) 2.26111/s t : 2X 3'3 /¢7 d) 5.11111/s - ‘ = O'LH 4— e) 1.641115 ‘1: : I. m / vi,“- [UK Q, Z+>/O m3 = 3,35?‘ :6— 1.4 m4 rm : ~ Two forces act on afibody of mass 6 kg. F: has a magnitude of 12 N, and acts to the right. F2 has a magnitude of 12 N and acts to the left. The acceleration of the mass is:_;a g; be} . F -” —7 —7 @ 0111/82 <—z——rl:l F\ [F.\ — ‘FL‘ 1)) 2 Iii/s2 a ~7 C) 12111/s2 _ _ F, 4’ F; 3 (9 d) 4 111/5;2 —7 , e) 72 111/s2 9 Q’ ~ 0 A mass of 2 kg is in contact with a horizontal plane and is moving horizon— tally due to an external horizontal force of 6 N. The coefficient of kinetic friction between the mass and the plane is 0.25. What is the magnitude of the acceleration of the mass? Assume g r 10 111/s2. A @ 0.5111/s2 2115 G M A b) 20111/s2 l l” ‘9 K c) 1.0 Ill/S2 /(’L: 0. 25 w) d) 60111/52 1? _ 6 __ 2x0,25 $.10: 1 [/71 :’W\& e) 3.0 rn/s2 11:; , a m a : 3-" : 0; b 5 2. A 5.0 kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at 2.6 111/ 82. What is the tension in the string? a) 49 N / I 6) 36 N f; c) 02 N d) 13 N 3&3 e) 52 N l ”‘57 4,) ———) ——7 m3 —L T -: YY‘ CU slam—T = 512.1) T : 5(‘7.9— 2.5) = 36 M 5. A block of mass 3 kg is pulled up a frictionless 30° incline by an applied force of 25 N in the direction parallel to the incline. What is the magnitude of the resulting acceleration of the block? a 3 m 5 1051 )1 F ‘f” ' ' 0 a) 4.6m/s2 95.0 (9 F3, / {F’IIP “mgrAl/st // 2.3 s2 \ J” P 9 , i 1:; 4.913% “/1. lFiv+l‘lt7+ 5,}:25 “”35“" 0 D d) 2.9111/52 33/0 . WW7 : H)“ = ’YY‘Q 3.4111/s2 V (6 \O A, 4- m. Obt 3-- = 3. 5; 6. When a spring is stretched an external agent to a. distance of 5.0 in from its equilibriui‘i'i position. the restoring force (the force exerted by the spring) is 10 N. What is the amount of work that is done by the external agent in stretching the spring to 5.0 m'? al50J :ule :ioN =>le=2fl 1))500J l: 9,“ fl" @25J 5m 3 d) OJ W" Sid = kaz 3i”, 25 : 25$ e) 25w ' 0 X 2. a 02 7. On a snowy October afternoon, you take a walk with your dog Newton, pulling an empty sled behind you. You pull the sled for 100111 at a constant speed of 3 in/s by applying a force F1 at an angle of 300 above the horizontal. You then tie Newton to the sled. and he pulls it for 200111 at a constant speed of 6 in/s by applying a force F2 that is directed along the horizontal. Which of the following is a true statement“? / O / a) Elie total work done on the sled when Newton is pulling is twice the work you do while pulling 2:01] as 30") >4 (00 m ‘3? O b) The total work done on the sled when you are pullirpflés 1/4 of the Work Newton does while pulling : F2 1 Zagmdp C) 0 ® he total work done on the sled when Newttfii‘s panning is the same as {he total work done on the sled while you are pulling} —_—. O (l) The work done by friction is larger in magnitude whe i on are pulling a ___; than when Newton is pulling. “94+ W ‘5 O :57 Eh... = O “:7 F : ~— F ‘ . - . -. . , 59'“ fr'cfim e) None of the forces acting on the sled do work.1 9V W, mcgfl WOW/£114) fixer-ton does W , m . 9. 10. A 2.0 kg block is moves down a plane that makes an angle of 20° with the horizontal with an initial kinetic energy of 2.0 J. If the coefficient of kinetic friction between the block and the plane is 0.407 how far will the block slide along the plane before coming to rest? Assume g = 10 111/82. @ 3.0111 _ __ _1_ «f3 1)) 1.8111 Kg” : 240 I ~ 2 Tn] L C) 0.30 In UK : xii—2': : i, LH S ‘ d) 1.0111 F: Qflma-COOG +WQ’W‘6 e) 1.3111 :flo'axizozofiq + wx0~3¥ ~7.52 + éflf 3.015% A pendulum bob that weighs 1 N is held at an unknown angle 6 from the vertical by a 2 N horizontal force F as shown. The tension in the string supporting the pendulum bob 1s: ‘ Two blocks of 6 kg each are connected by a string that passes over a niassless pulley as shown and are moving with a constant acceleration. Neglect friction. Assuine g : 6 [Q9 10 111/82. The tension in the string is: “3 a) 60 N b) 120 N T, c) 20 N 6% T d) 0 N M a; mg, m @ 30 N 6 .1 o “it 0t —' : 5' £1 i2 5‘ m3) — T: YHCU m ( 6A v- a) ‘— T c < \UP5) - T 3 0 N 7 T 11. An object is constrained by a cord to move in a circular path of radius 0.5 m on a horizontal frictionless surface. The cord will break if its tension exceeds 16 N. The maximum kinetic energy of the object is: o 44 4 W; b) s] ”E" , 16J , 405:3 (i; 32.1 “View: TM“ R T H” 7.. e) 64J 12. Peter is driving east in the right lane of a highway at a speed of 31 m/s. George is in the left lane and driving west at 18 m/s. What is Peter’s speed, in m/s, relative to George? , - f m a) 49 West 63‘ M 3 l /5 , b) 13 West W, C ”‘J’ EMT @ 49 East M Q d) 31 East "Ll- e) 13 East 13. A biology book lies on top of a physics book which lies on top of a horizontal table as shown. Which of the following is a Newto— nian action— reaction force pair? a) The weight of the biology and physics M W 19¢ka “—7 oft/1M NOT books and the normal upward force of WW {1% ”D hawks PM the table on the books. b The weiO‘ht of the biolo‘ book and ) the nornfal upward force ifthe physics ' ’ NOT PM book on the biology book. c) The downward force ofthe physics book P MSW: boat” 2 on the table and the upward normal M, force of the physics book on the biol— PW“ bah) 7 b 0’97 beak / ogy book. @ The upward force of the physics book on the biology book and the down— ward force of the biology book on the piwmm e) The weight of the physics book and the weight of the biology book, as- suming they both have the same mass. Pfilaovf/L—afl/M’Cf/t K) ' lowyo books M? O’Tpm 14. A block of 1.0 kg mass is pulled from rest on a frictionless horizontal surface by a constant force applied in the direction of motion. After the force applied over a distance of 12 in, the speed of the block is 2.0 rn/s. What is the magnitude of the applied force? a 6N Afi-Eiw" FA | ' Z Fd (:l)0.17.\1 :imU1:,,’,Lf: if: ',' c) 1.0N AKE Z 1 ’12 (1) MN 2 _. “L N J 0”,?“ e) 0.085N :- Ti: ~ g — A sign is suspended from a wall by a horizon— tal bar attached the side of the sign nearest the wall and cable attached to the other side, as shown in the figure. Which of the follow— ing force should NOT be included in the free body diagram of the sign? a) The tension in the cable. @ The force of the sign on the bar. c) The force of gravity on the sign. ('1) The force of the bar 011 the sign. ) e All of these forces should be included. ...
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