Physics_7A_-_Fall_2003_-_Yu_-_Midterm_1

Physics_7A_-_Fall_2003_-_Yu_-_Midterm_1 - Page I all...

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Unformatted text preview: Page I all Physics 7A Section 1 Fall Semester 2003 First Midterm Sept. 29, 2003 (6:10-7:40 pm) Instructions 1. This is a closed hook exam. You are allowed to bring along on! - one 3’56” "cheat sheet", pens, pails. scientific calculator, and blue books. 2. Read all questions carefully. Attempt the easiest ones first. 3. Write your name, Discussion Section #1, GST name and SIDEI on the trip of'all malet‘ials you intend to hand in and want to be graded, 4. While cleanliness and legibilily oryour hand—uniting will not get your extra credit, they will help to make sure that your answers get the credit they deeerve In case you make mistakes be sure to cross them out so they will not he mistaken as your answer. It helps to put _ I at box or Circle around your final answers. 5. Partial credit You wiil get typically 90% of the total credit ifyou can either derive your equations or show how the equation you wrote down from your cheat sheet can be used to answer the question in terms of symbols you have defined. When you Substitute numb-tars into these symbols to obtain a numerical answer, make sure that you specify also the units. On the other hand, a pure numerical answer without caleutaiion to support it will get no credit. You are provided with the following constants for your reference There. is no guarantee that they will ail he required in solving, flie problems. Useful Constant: n=3.1415-, greens W51; 1 mjle=].ol Km. 1 mph=0 44': mo; PaggZ-Elfd- fluestion I (total: 20 Points] The advertisement for a sports car claims that the car can reach a speed of 60 miles per hour (mph) from rest in 6 seconds. A sports utility vehicle (SUV) advertisement claims that the car can reach a speed ot'ofl miles per hour [mph] in 13 seconds. (a) Assuming that both cars can achieve :r'usi‘anianetmsbJ their maximum acceleration, What are the distances {expressed in miles) covered, respectively, by these two ears when they reach 60 mph? (In) The masses of the sports car and SUV are [250 Kg and 2300 Kg. respectively. What are the threes produced by the two car’s engine, assuming that there is not friction from the road and no air resistance? (c) What will be the forces produced by the [we ear‘s engine to obtain the same acceleration if there is friction and thal lite eoefl‘ieient of kinetic Friction between the rend and the tires on both cars is 0.1? Air resistance is assumed to be negligible. Question 2 itnta]: 2t] Poinlsl An artillery wantto hit a target located at a distance of 1.8 Km away. (:1) Suppose the artillery can fire shells with a maximum speed ot‘U.2 Kim’s what should he the angle of“ tilt (G) of the canon to the ground in order that the shell will hit the target? (b) What should he tilt of the canon in case the target is located on a slope inclined at 25" to the horimnlal as shown in the figure? The distance between [he artillery and the bottom ofthe slope is O. 5 Km while the target is at a distance of I. 3 Km from the bottom of the slope. ll'you find two amptnble tilt angles which one will you ehose assume lhai. you have to fire the canon? In this qu estion mgfect the height Ofelia tame: and moon and also the air rea'istwtce. Target Artillery h——'1 0.5 Km Question 3 (total: 20 Point!!! A small block of mass 20 Kg is resting on a larger block of mass 30 Kg. The two blocks are testing on a table A force 'F is applied to the large block as shown in the figure on next page. Pngg J of 4 (a) The TWO blocks famain Stationary with respect to the table until F=4O N when the lwo blocks start to move together. What is [he caefiicient of static friction between the large block and the table? fh] Once the two blocks stm moving the cuefl'iuiem offriciion betwemi the large block and the table quickly drops to the value 60.05 for kinetic friction, what is the acceleratinn oft he two blocks? (c) Suppose the coefficient of static friction between the small block and the large block is 0. ]. What will he the force when the small block starts to fly nfl'the large block? 20 Kg 30 Kg flufiun 411mm: 20 Points} A windnw cleaner and his platform has a tnlal mass of I'm Kg. The plail‘orm is suspended from a I'ricfiuulcss and massless pulley,r by a. counter weight 0|" 100 Kg. as show in figure: Pulley Gaunter ‘Window Weight Cleaner 3: Platfoml Assume [hail the rope has no mass also. (3} HOW muCh force Shnuld the winduw ulmner apply to the rope in nrder that he can raise himself slowly at n mnslanl speed? Gil? y'cmr answer 10 J .tfé‘mificrzmfismres, Page ~$ of 4 (b) Suppose the window cleaner is as-cemflng with a constant speed 01113 "Us towards a window at a distance of 5 m above him. What Force sh0uid he appiy new in order that he will stopjust in Front. ofthe window? Give your answer m -]l .s'rgurfimnrfigurex. Question 51mm: 20 Points] Tn a Circus :1 dare—devil performer can go around a steel Spherical Gage (olfadius 3"— 10 meters) on a motor—cycle so fast that his molot—eycle becomes lloriwulal as shown in the figure! The coefi'leiems of static and kinetic friction between the motor—cycle and the steel cage are (18 and [)5 respectively. (a) What is the speed of the motor—cyclist in order to ride around the cage in this horizontal position“? {b} AS the motor-cycle slows down the angle El} between the motor-cyclist and the vertica] deereaeee: From 90°. What should be the speed of The motor-cyclist when t1) equals to 45". ———EN'D or QUESTIONS —————————— .... ...
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This note was uploaded on 04/01/2008 for the course PHYSICS 7A taught by Professor Lanzara during the Spring '08 term at University of California, Berkeley.

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Physics_7A_-_Fall_2003_-_Yu_-_Midterm_1 - Page I all...

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