Sample Exam 2 Key

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School

West Virginia University *

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241

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Physics

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Oct 30, 2023

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Uploaded by CoachFog5896

SAMPLE EXAM TWO Physics 111 (Date of exam will be here) Write your Last Name, First Name, PHYSICS NUMBER below: Correctly recording your physics number and course information earns 3 points. Key : by writing my name I swear to follow the student code of conduct at WVU And circle data for your LAB on three lists: My LAB Day of Week: Tue Wed Thu Fri My LAB Time: 8:30 11:30 2:30 5:30 My LAB Room is at the end of the hall. TRUE or FALSE And also circle the name of your LAB TA on this list: [real last names of TAs will appear here; circle yours on the real exam please...] And also circle the start time for your LECTURE on this list: My LECTURE Time is: 8:30 9:30 10:30 11:30 12:30 1:30 2:30 Table 1: Table for grading use only, lowest problem score from (2, 3, 4, 5) not counted in TOTAL Score. Info (3) || MC (32) || Prob 2 (15) | Prob 3 (15) || Prob 4 (15) [ Prob 5 (15) ][ Prob 6 (20) || TOTAL (100) Read all of the following information before starting the exam: o This test has a short answer section (worth 32 points) plus four half-page problems (each worth 15 points) and one full-page problem (worth 20 points). Your lowest half-page problem score will be omitted, so the overall exam (with 3 points for ID data) is worth 100 points. e Even if your final answer is correct, for full credit, some evidence of your solution or explanation is necessary. Show all work. Circle or otherwise neatly indicate your final answers. ® You may use a simple scientific calculator on this exam. No programmable calculators, cell phones, or other devices arc allowed. Have enough pencils or pens with you to complete the exam. * You may not have ANY electronics with you during the exam aside from the simple calculator. All your belongings (backpack, cell phone, watch, music player, headphones, etc.) should be placed near the front of the room or (better) left home. Breaking this rule will will invalidate your exam. e A valid exam represents your work and your work alone. Do NOT talk to others during the exam, do NOT look at others’ exams, do NOT share calculators. You may not leave the room during the exam. o If your behavior during the exam, or your exam as submitted, suggests that your exam is not wholly your own work, you will receive a zero, and you will be reported for academic dishonesty with serious academic consequences. e Show your student ID when turning in your exam. Good luck!

Physics 111 Sample Exam 2 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. On the real exam, you will have to mark your bubble sheet and provide your student ID. 1. A car traveling at 100 km/hr strikes an unfortunate bug and splatters it. The force of impact is 1. A. the same for both. B. greater on the bug. C. greater on the car. 2. Astalled car is being pushéd up a hill at constant velocity by three people. The net force on the car is 2. A. down the hill and greater than the weight of the car. B. up the hill and equal to the weight of the car. C. up the hill and greater than the weight of the car. D. down the hill and equal to the weight of the car. E. zero. 3. A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked ~ 3. quickly. This best demonstrates that A. the milk carton has no acceleration. B. the milk carton has inertia. C. gravity tends to hold the milk carton secure. D. there is an action-reaction pair of forces. E. none of these 4. If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's 4. kinetic energy. A. True B. False 5. If you find that twice as much work is needed to perform a task but it takes twice as much time, the 5. amount of power required is A. sixteen times as much. B. twice as much. C. four times as much. D. unchanged. 6. When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal 6. speed. Once he has reached terminal speed A. the force of air drag on him is equal to his weight. B. his acceleration is equal to g. C. his speed is equal to g. D. the force of air drag on him is equal to zero. E. the force of air drag on him is equal to g 7. A ball drops some distance and gains 30 J of kinetic energy. Do NOT ignore air resistance. How much 7. gravitational potential energy did the ball lose? A. more than 30 J B. less than 30 J C. exactly 30 J 8. A car's engine is 20% efficient. When cruising, the car encounters an average retarding force of 1000 N. If 8. the energy content of gasoline is 40 megajoules per liter, how many kilometers per liter does the car get? A 12 B. 8 C. 10 D. 14 E. none of these

9. Neglecting friction, a small and a large block of ice begin sliding down an incline side-by-side (but not connected). The larger block reaches the bottom A. at the same time as the small block. B. before the small block. C. after the small block. 10. A flower pot of mass s falls from rest to the ground below, a distance 4 Which statement is correct? A. The speed of the pot when it hits the ground depends on . B. The KE of the pot when it hits the ground does not depend on 7. C. The KE of the pot when it hits the ground is proportional to /. D. The speed of the pot when it hits the ground is proportional to /. E. None of these are correct. 11. Two identical arrows, one with twice the speed of the other, are fired into a hay bale. The faster arrow will penetrate A. the same distance as the slower arrow. B. more than four times further than the slower arrow. C. four times further than the slower arrow. D. two times further than the slower arrow. E. none of these 12. What horizontally-applied force will accelerate a 400-kg crate at 1 m/s2 across a factory floor against a friction force half its weight? A. 588N B. 1568 N C. 2360 N D. 1960 N E. none of the above 13. Atraveler pulls on a suitcase strap at an angle 36° above the horizontal. If908 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m, what is the tension in the strap? A. 92N B. 61N C.75N D. 85N 14. A force } =12N ?— 10 N}acts on an object. How much work does this force do as the object moves > from the origin to the point » =13 m ?+ 11 m}? A. 6217 B. 467 C.377 D. 2667 15. A plastic ball in a liquid is acted upon by its weight and by a buoyant force. The weight of the ball is 4.8 N. The buoyant force has a magnitude of 6.5 N and acts vertically upward. An external force acting on the ball maintains it in a state of rest. The external force, including direction, is closest to: A. 6.5 N, upward B. 6.5 N, downward C. 1.7 N, upward D. 1.7 N, downward E. 4.8 N, upward 16. Jason takes off from rest across level water on his jet-powered skis. The combined mass of Jason and his skis is 75 kg (the mass of the fuel is negligible). The skis have a thrust of 200 N and a coefficient of kinetic friction on water of 0.10. Unfortunately, the skis run out of fuel after only 48 5. What is Jason's top speed? A. 13m/s B. 130 m/s C. 81 m/s D. 48 m/s 10. 11. 12. 13. 14. 15. 16.

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2. (15 points) 1D Newton’s Second Law. Show your work and explain your reasoning. A gymnast of mass 64.0 kg hangs from a massless vertical rope attached to the ceiling. a. (3 pts) Draw the free-body force diagram of the gymnast. Clearly label all forces. F a b. (6 pts) Calculaté the tension in the rope if the gymnast is climbing up the rope at a constant speed of 1.15 m/s. a=o ZFy= 0 E—T—'g o = s F;':Wj :44%(?_?%):@2?‘21«/ c. (6 pts) Calculate the tension in the rope if the gymnast is climbing upwards but slowing down at a rate of 0.48 m/s?. §! 84k (1.6%-0%2) = 59658 3. (15 points) Equilibrium. Show your work and explain your reasoning. A 5.0 kg ball hanging from strings (see figure) is in equilibrium state. N | g feo Z v = O ‘ — 7-?:-.-'[:—:0 R =~y 7 —_ 22N e 7.:( - (:,« = —5Ac (?g;::) - fi/fN a. (5pts) Find the tension Tp. re g o b. (5 pts) Find the tension T) when the angle § = 30 degrees. c. (5 pts) Find the tension in the horizontal string, Ts. i éf‘i- o s ZF=o0 =0 =1 . R0 Ty R =0 (V Yo FT;__ F’:g,,\@ .rt C°5@= IWT‘.

4. (15 points) Ramp Work. Show all work and explain your reasoning. A block of mass 8.00 kg is pushed a distance of I = 3.00 m up a frictionless incline at a constant speed by a constant applied force Fu that points directly along the incline. The incline makes an angle of 30 degrees with respect to the horizontal. a. (6 pts) Find the work done by gravity as the block moves up the incline. wj:%‘[coscfi qS: /Zoo = 1Pty LCosp = ?kj(?'g?fsgm COE(’/ZO&) — 'MJ’ b. (3 pts) Find the work done by the normal force as the block moves up the incline. W= Fa £ Coc (90°) = O c. (6 pts) Find the work done by the applied force as the block moves up the incline. \/\/T " — A K ?* O rjvl rla /’avxs“;{rwt"' 5,’(¢z4 Wy W+ w, = 0 Waz-Wy= 176 T 5. (15 points) Frictionless 2D Motion. Show all work and explain your reasoning. Two blocks with same mass m are hanging on frictionless slopes. When the string attached to the vertical wall is cut, the blocks accelerate. What is the acceleration of the blocks? (Ignore the mass and the friction of the pulley and string.) Fy =rma 2 F, = mq 2_ F—' ia = o { T M3§ O=ma « + g Sind =i q

6. (20 points) Friction block, Show all work and explain your reasoning. A wooden block (mp, = 4.5 kg) is connected to a vertically-hanging mass m,, from a thread of negligible mass that goes around a frictionless pulley. The wooden block is on a table top with a coefficient of kinetic friction of 0.20. The block is released from the rest and immediately begins sliding. a. (5 pts) Draw free-body diagrams for the block and the hanging mass. N [ —F £ 2 7 T T F > — j; > # a — “ Fae 79 b. (5 pts) If the block"started to move with an acceleration of 1.0 m/s? to the right, what is the tension of the thread? Fr,“ /—“:;: m, G f”f‘:%a =0 Fr= o0+ M Fy=13.32 9 Fo=m3=1.1n c. (5 pts) What is the mass 1, in kg? ZF,. = mu(-a) - Fr Br MG T -G 2 Fr = Ma§ - MG D= G-a = .51 s d. >(5 pts) Sketch the velocity of the sliding block on the following velocity-time graphe——— ./ before and after the mass hits the ground. (Assume that the block remains on the table top throughout.) Released Hanging from rest mass hits here. floor here.

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