111_Midterm_part3 - Page 1 of 7 Midterm Physics 111 —...

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Unformatted text preview: Page 1 of 7 Midterm Physics 111 — Prof. Honscheid 10:30 PM, October 24, 1994 NAME Rec. Instructor . Grade __ - Lab Points __ " Two significant digits suffice. " Exam is closed book, closed notes. Calculator allowed (but memory must be cleared before exam). " Write yomnsme and the name ofyour recitation instructor on'every page of the exam. " This exam consists of two sections: a Section I: Two lob questions (graded separately from midterm) a Section II: The second Midterm Exam (this purl will be curved) Part A: Ten multiple choice questions (5 pts each) Part B: Two problems where you are required to show work ' You have 48 min to complete both sections. Don’t get stuck at a single problem for too long. " Acceleration due to gravity = g = 9.8 111/52, downwards NAME Rec. Instructor Page 2 of 7 Prof. Honscheid, 10:30 pm section, October 24, 1994 SECTION I: LAB QUESTIONS (5 pts each). Write the letter for the best answer in the space provided. Question 1: In a force table experiment, three forces F1, F2, and F3 balance each other. The components ch1sre F1;=4N,F1y=1 N andthe components osz arerx - 1 N, F23 == 3 N. Ifyou place the tails of all force vectors at the origin of the coordinate system. in which quadrant does F3 point? Y _ a) Quadrant I b) Quadrant I] 11-. I . c) Quadrant In x ' d) Quadrant IV III IV Answer Which graph best represents the relationship between velocity and time for an QuestionZ: object which accelerates uniformly for 2 seconds, then moves at a constant velocity for l secondand finally decelerales for 3 seconds? ‘1' a.) ‘V _ 123456Is] 123456ISJ 'l: I“. 123456Is] 123456Isl 1; 1: Answer: NAME Ree. Instruch Page 3 of 7 Prof. Household, 10:30 pm section, October 24, 1994 Section II: Midterm Examination Part A: Multiple choice questions. Write the letter preceding the best answer in the space provided. (5 pts each) 1. 2. Why do you push harder on the pedals of a bicycle when first starting out than when you are moving at constant speed? (answer) ' (it) Because fiction and air resistance are larger when you first start. (b) Because you mass is larger when you first start. (c) Because you must accelerate the mass of you and your bike. (d) All of the above. (e) None of the above. A 5.0 kg male is given an initial speed of 20.0 ran and then allowed to slide across the floor until it is stopped by a retarding forces (friction, air resistance etc.). What is the magnitude of the retarding force acting on the crate if it slides 9.0 in before it stops? (answer) (a) 22 N (b) 111 N (c) 100 N (d) 45 N (e) None of the above. Joe walks 4 blocks north, then he turns east and walks 1 block. He finally walks 3 blocks south. How far is Bob away from his origin? (answer) (a) 0 blocks (b) 8 blocks (c) 1.4 blocks (d) 1.? blocks (e) None of the above A motorboat whose speed in still water is 3.5 mfs must aim upstream at an angle of 47° (with respect to the shoreline) in order to travel directly across the river. What is the speed of the current? (Hint: draw a vector diagram of the relevant velocities) (answer) (a) 3.7 m/s (b) 3.5 mls (c) 2.6 m/s (d) 2.4 m/s (e) None of the above 33 NAME Rec. Instructor .._, Page 4 of 7 Prof. Househeid, 10:30 pm section. October 24, 1994 5. On a planet far away in the Gamma quadrant, a rock falls 3 distance of 72.0 m in 3.60 s after it is 7. released from rest. What is the acceleration due to gravity on this planet? (answer) (a) 9.81 W32 (b) 20.0 m2 (c) 1 1.1 nvsz (d) 3.3 111/82 (c) There is no gravity on other planets An airplane travels at a speed of 655 kmlh for 1.5 hours and then speeds up so that is travels with 905 ion/h for the next 2.5 hours. What was the average speed of the plane during this trip? (answer) (a) 655 km/h (b) 780 Ian/h (e) 811 Ion/h (d) 905 kmfh (e) 764 kmfh You are driving your car a bit too fast. 103 Imv'h. that is 20 Irmlh above the legal speed limit. You suddenly see a police car. 60 m firrthcr down the road. You immediately hit the brakes (we ignore your reaction time) and decelerate with 3 mfsz. How fast will you be, when you pass the police car (we assume you stay on the brakes and your deceleration is constant)? (answer) (a) 106.3 m/s (b) 23.2 mls (c) 20.0 mfs (d) 18.2 mls (e) None of the above An airplane whose airspeed is 550 lrmfh heads due north. But a 80 kmfh wind, coming from the east, suddenly begins to blow. What is the magnitude of the resulting velocity vector of the plane with respect to the ground? (answer) (a) 550 kmfh (b) 630 imu'h (c) 556 tenth (d) 544 krnfh (e) None of the above NAME Rec. Instructor Page 5 of 7 Prat. Honseheid, 10:30 pm section. October 24. 1994 9. You throw two stones from the edge of a cliff. The first stone (A) is thrown with an initial speed of 5.0 W8 straight down. The other stone (B) is thrown straight up, also with an initial speed of 5.0 m/s. Which of the following statements is true? (answer) (a) Both stones have the some velocity when they hit the ground. (b) Stone (A) hits the ground with a larger velocity than stone (B). (c) Stone (A) hits the ground with a smaller velocity than stone (B). (cl) The heavier stone hits the ground first. (e) None of the above. 10. A 6000 kg helicopter accelerates upward at 0.0 me? while lifting a 1500 kg car. What is the tension in the cable (ignore its mass) that connects the car to the helicopter? (answer) (a) 15600 N (1:) 14700 N (c) 900 N (d) 78000 N (e) None of the ab0ve NAME Ree. [Munster Page 6 of 7 Prof. Honscheld, 10:30 [in section, October 24, 1994 Part B: Problems. You must show all work and all intermediate steps'to receive full credit. Sketches and disgust: are often useful. Write down the formulas you are using. Problem 1: It's allmost that time of the year whimdSmtaClausis gettingready. Whenthe reindeer: pull the sled with a force of 800 N through the snow, it is moving with a constant speed of 5 mls. As indicated in the drawing, this fore: is appliedunder and angle of 30° with respectto ground. The mass ofthe empty sled is 200 kg. (Note: the reindeer is just the source of the pull force. Don’t draw a fit: body diagram for the mindcerll Rudolph wouldn't like it) Angle = 300 Part 1: Draw the free body diagram of the sled. Include all forces. Part 2: What is the magnitude of the retarding force excerted onto the sled by the snow? Part 3: What mass (to Christmas presents) can be loaded onto the sled so that the normal force escorted by the ground onto the sled stays below 3000 N. The reindeer keep on pulling with the some constant force of 800 N independent of the load. Page 7 of '7 NAME Rec. Instructor Prof. Household. 10:30 pm section. October 24, 1994 Problem 2: A projectile is launched at an angle of 60° with respect to the horizontal direction with an initial speed of 8.5 oils. The projectile startsataheightoftmmabove ground. Part 1: What are the horizontal and vertical components of the projectile’s initial velocity? Part 2: How long does it take the projectile to reach the ground? Part 3: Where does the projectile strike the ground (displacement from the bottom of the wall) Part 4: What‘s the highest point of the projectile above ground? 33 Name __.________——— PART A. True-false (4 points each. 24 points total). Circle the letter representing the 12:30 PM The sum of three vectors of magnitude 3, 4. and 5 units can have a resultant of magnitude zero. Attack thrown widtaoenain speedfrornthe topofaelifi'will entathe waterbelow with a speed that is the same whether the rock is thrown horizontally or at any angle (in the absence of friction). A 10.0 kg block and a 20.0 kg block are released together from rest near the top of a frictionless 30" 'nclined plane. Assuming the blocks are identical except in their mass, the 20.0 kg ball will reach the bottom first. Newton’s laws do not apply to systems in the presence of frictional forces. In the absence of air resistance the vertical component of the velocity of a projectile is constant. Two cars approach each other on parallel lanes, each having a speed of 150 ion/h with rpspaci'tgg lthe earth. If they are initially 30.0 km apart, they will pass each 0 er in . . Page 2 of 5 Rec. Instr. ._ _____ ._.__._.._.___. be51 answer. PHYSICS 111 mm EXAMINATION OCTOBER 24. 1994 Dr. Sugarbaker 12:30 PM Page 1 of 5 Name Ree. Instr. Grade 1. Input numbers should be assumed good to three significant figures. Your answers should also be good to three significh figures unless otherwise indicated. - 2. Exam is closed book. Calculators allowed. but calculator memwy must be cleared before exam starts. 3. Write your name leginy and your recitation instructor's name on each page. 4. ‘fitis examination consists of: PART A: 6 mic—false questions (4 points each) PART B: 5 multiple choice questions (5 points each) PART C: 3 problems (Problems C1. C2. and C3) (all work needs to be shown, 51 points total) The scores on the exam will be curved. 5. Check now that you have a complete exam. 6. You have a total of 48 minutes to complete all sections. NEGLECT AIR RESISTANCE. Values of physical constants: Magnitude of acceleration of gravity at Earth’s surface = g = 9.80 111/52 Dr. Sugarbaker Name 12:30 AM Page 3 of 5 Rec. Instr. _______________ PART B. Multiple Choice (5 points each. 25 points total). Circle the letter preceding the best answer. 7- 10. 11. A race car takes 200 s to do four complete laps around a five kilometer track. Its average velocity for the four laps is (in ion/s) . a) 0.000 b) 0.100 c) 0.200 d) 10.0 e) none of the above. A vector A has a ma 'tude of 20.0 units and is directed West. A vector B has a magnitude of 5.00 unitsandisdirected t. “IlievectorC= A- Bisavector a) of magnitude 25.0 units directed East. 1:) of magnitude 15.0 units directed East. c) of magnitude 25.0 units directed West. d) of magnitude 15.0 units directed West. e) of magnitude zero. A block slides down a frictionless plane at an acceleration of 4.90 mfsz. The angle 8 with which the plane is inclined to the horizontal is (in degrees) a) 20.0 b) 30.0 c) 45.0 d) 60.0 e) acne of these A 200 kg mass is being pulled vertically upward by a massless cable with an acceleration of 3.00 111/52. The tension in the cable is (in N) a) 600 b) 800 c) 1960 d) 2560 e) none of these. When a net horizontal force acts on a mass, it produces a horizontal acceleration a) only if the force is larger than that weight of the mass. 13) only if the mass is at rest. c) in some cases but not in others. 15) in every instance. 36 Dr. Sugarbaker I 12:30 PM Page 4 of 5 Name Rec. Instr. . ._ _...._ _._ PART C. Problems C1, C2. and C3 must be worked in detail. W to receive any credit for the correct answers. 111:: point value of the problem is shown in brackets. C1. A 20.0 kg block sits at rest upon a plane inclined at an angle of 20.0‘ to the horizontal. as shown. a) LIST below and SHOW on the drawing ALL of the forces 15} acting on the block. y b) Determine the magnitude of the friction force [8] which keeps the mass from sliding down the plane. c) Calculate the coefficient of Static friction between the block and the plane assuming this angle [8] represents the maximum angle before which motion of the block would begin. Begin from BASIC equations and definitions! C2. If A = (2,-8.3) and B = (52,-2). using the notation that the vecer [10] has components (anrvz). Determine the vector C (using similar notation) such thatC +A=B. a"? Dr. Sugarbaker 12:30 PM Page 5 of 5 Name Rec. Instr. C3. In Acapulco. divers jump from a 36.0 m high clifi' into the sea. At the base of the cliff, a rocky ledge sticks out for a horizontal distance of 6.40 m. Assume that the divers jump off with zero initial vertical velocity. NEGLECI‘ AIR RESISTANCE. a) How long are the divers in the air? (in s) b) With what minimum horizontal velocity must the divers jump off if they are to clear the ledge at [7] the bottom? (in mls) [IF you couldn't work part a) assume its answer to be 3.00 s to continue here] c) With what vertical velocity does the diver hit the water? (in 11115) [5] [IF you couldn‘t work part a) assume its answer to be 3.00 s to continue here] 33’ ANSWERS TO SOME OF THE SAMPLE PHYSICS lll MIDTERMS ,(Note: * means that the material is not included in midterm this quarter} I. EPSTEIN: Jan. 30, 1991 Part I. 1. F 2. F 3. F 4. F 5. F Part II. 6.‘B 7. D 8. A 9. B 10. A 11. B fiJ Part III. A. i] .nvs ii) 3.2 m/s at 72" N of E 3 %% R A E B. a z —204 m/sm x t = 0.17 5 C. a) 255 m/s b) 255 m/s C) 72 s d) 10 km e) 18 km II. RALLIS: April 20, 1992 Section I. E Section II. Part A. 1. B 2. A 3. A 4. D 5 C 6. E 7. E 8. B 9. C Part B. B1. 10 m/s B2. a) 4.0 s b) 49 m B3. 26 min B4. a) 3.7 m/s at 64° N of E b) 24 s; 39 m III. EPSTEIN: 25 Feb 1991 Part I. *1. T 2. T 3. T *4. F 5. F Part II. 6. E 7. A 8. D *9. B *10. C *11. D- 3 Part III. *12. *a] 7.1 x 10 m/s 1 o *b} 1.2 x 101 J *c} 22 F»! r 13. 6.} Pg Ft;- F? 3 4 4 b) 2.0 x 10 N *c) 1.1 x 1 w *d) 2.0 x 10 w Iv. RALLIS: May 13, 1992 Section I. 1. B *2. C Section II. Part A. 1. E 2. D 3. B 4 A *5 B 6. B *7. D 8. B Part B. ' V (— M (1.. x *Bl *a) no *c) ‘l’ C. *b) 9.9 m/S F: '2. I Fé’ N *d) 1.3 x 10 N stralght down F: N >’ . "Z. v E. b) 84 N c) 9.1 N d} 1.4 x 10'2 J e) 0 V. HONSCHEID. Oct. 24. 1994 Section I. l. C 2. A Section II. Part A. 1. D S. . C 9. Part B. 1. 2. v =4.3 m/s v = 7.4 m/S t=1.95 maxy 6.8 m ...
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111_Midterm_part3 - Page 1 of 7 Midterm Physics 111 —...

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