p140w09_mid1_solutions - Physics 140 Winter 2009: Exam #1...

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Unformatted text preview: Physics 140 Winter 2009: Exam #1 Please print your name: Please list your discussion section number: Please list your discussion instructor: Instructions 1. Fill in your name above; version number can be found at the bottom of the page 2. This will be a 1.5 hour, closed book exam. The exam includes 20 questions. 3. You may use a calculator, please do not share calculators 4. You may use one 3”x5” note card with notes and equations you think may be useful. You can write on both sides of the card if you like. 5. You will be asked to show your University student ID card when you turn in your exam. Mike Melnichuk 1 024 3-4 1 025 11230-1 i 026 1-2:30 Wayne Lau 004 8-9 005 9—10 006 10—11 012 3-4 014 1-2 015 2—3 Dave Winn 008 9-10 009 10-11 Timothy Cohen 010 8-9 011 9—10 Catherine Home 016 12—1 01? 1—2 018 2-3 E Ross O’Connell . 023 2-3 3 Vivek Narayanan 5 019 1-2 5, 020 2-3 021 3-4 Version 1 Page 1 1. The system shown remains at rest. The coefficients of friction between the block and the plane are: lug = 0.75, pk = 0.5. What is the magnitude of the force offrietion on the upper block? Use the following to answer questiori 2: .__ X M A system of two cables supports a ISO-N ball as shown. 2 __ M m} 5.“ Q9 \. 5‘...“ as: a. 5 ‘\ —- {pi ‘J g Ta *7 s ._ . \ ‘1 Co (a > \0 §. 6—H» " ‘ ‘ e ’ 1““ q K 5 I w V gF - 7.19.469 —-w :‘o I) 2. What is the tension in the horizontal cable? _ a W A) 300 N {a “ ‘ '2' 3 00M B) S. ’1 C0 260 N D) Elias? ficOs@‘—? =6) E) 17'0 N ’V 9.6 O N Version 1 Page 2 3. A heavy steel ball B is suspended by a cord from a block of wood W. The entire system is dropped through the air. Neglecting air resistance, the tension in the cord is: A) the difference in the masses of B and W B) the difference in the weights of B and W C. the weight ofB ' none of these 1%. qc{$‘ 0"? {W find-j? mp (Um? SE2 Thwm:“”89 ’ 0 $3133“ Mvath‘kaa 4. A car moves horizontally with a constant acceleration of 3 mst. A ball is suspended by a string from the ceiling of the car; the ball does not swing, being at rest with reSpect to . What angle does the string make with the vertical? A) 43:; B) 35° C) 52" D) 73° E) Cannot be found without knowing the length of the string Version 1 Page 3 Use the following to answer question 5: Two blocks rest on a horizontal frictiofless surface as shown; The surface between the top and bottom blocks is roughened so that there is no slipping between the two blocks. A 30-N force is applied to the bottom block as suggested in the figure. Kb?” 6%: .___H\ 5. What is the force of static friction h'etWEEn the t0p and bottom blocks? A) N “ a... I A B 5 N E F “I: g C) N ‘“ l S— K‘j Q m» 60*“ a / t“ I 'I N G E) zero newtons Use the following to answer question 6: A lOOO—kg Jeep travels along a straight 500-111 portion of highway (from A to B) at a constant speed of 10 mfs. At B, the Jeep encounters an unbanked curve of radius 50 m. The Jeep follows the road from B to C traveling at a constant Speed of 10 mfs while the direction of the Jeep changes from east to south: I I Version 1 Page 4 6. What is the magnitude of the frictional force between the tires and the road as the Jeep negotiates the curve from B to C? A) 10000N ' L B 1000N ZF’Q“ “V 2; gooom D) 20000N j“- V E) SOOON 01/ :9 Q0”; p 9°w¥q/ Use the following to answer question 7: o D Q Qp mg g C Mi ~—~‘=> amissmile”'" " 2 F1 2 135 ~ 017‘ ‘3 O .AT 1‘. ER: T“WI“3:O lee rzwfi 7. In a homework assigmnent you computed the acceleration of block 1 under the assumption that no force of friction acts on block 2. How large a force of static friction would be needed between block 2 and the table to prevent the system from moving? D) f3 = 0.5 mg E) Impossible to say, since we don't know the coefficient of static friction. Version 1 Page 5 8. One of the triggers of the 30 years war in Europe was an event called the "Second Defenestration of Prague". The citizens of Prague threw several representatives of the Holy Roman Emperor out ofa window 16 meters above the ground. The representatives landed in a pool of horse manure and survived the fall unharmed. Assume that the pool of manure was 1 meter deep and estimate the force exerted on one of the falling representatives by the manure. N {- O k I 6 A)_..J__X__l_9:lj~x I m M 0 OJ ,. M 2 q I - no” 5 ~>+o V: = U: + 51:3 5" gran-.3"; \ x c J“: -&a(4 *JD) 1x 10' N \ O R‘- ro “(/5 “L ° mg E2 1x10°NC = 3QO.sf/sa .3 ': (,0 -- O °~ a +1“ MW": v: + as cine See's F .. Mail 9. Dr. Evil jumps out of an airplane without his parachute. Mini-me grabs two parachutes m { and jumps after him, hoping to save his life. Given that Mini-me is an exact replica of (9 0°C) N Dr. Evil but with all relevant length dimensions reduced by a factor of eight, what will N r I Q [0% happen? _ ‘ 0" ‘3 A) Mini-me can catch Dr. Evrl if he lets go of one of the parachutes. a». 52.151! B) Mini-me will catch Dr. vil if the plane is high enough above the ground. ( . .3- Ir 0 “t M ill catch Dr. Evil if the mass of the two parachutes is big enoug . 3 F“! a . . m l‘ 511 catch Dr. Ev1l. _ HI _ ad start. ‘ 63"“ w/ Cur. regal-e1 cg w/c; air rem: atflw 3 View»: 0L AHQ 3 AMUA 90 “(rs {rel-2 )‘t- 5: (j ' 6K 55 M 9% f"(BA £3 .. _ u ? Q Ujfl‘ ’4 “f 2 was 1 a...) : cm... .s =- we UW‘H, QVl-f : 8 VT‘UM , “15.40 Mr‘flr‘ --- M WHO’S 144 a. § 5 he <32 “inf-t UP 10. Suppose you turn on the light in a cheap motel and see a cockroach scurrying directly away from you at a constant speed 1.40 mfs as you move toward it at a Speed of 0.740 mis. If you start a distance 0.860 m behind it, what minimum constant acceleration would you need to catch up with it when it has traveled a distance 1.40 m, just short of safety under a counter? (SD ---—'> “'0 o =- C” '7 4 m ,5 AHQOSmfsz MQ j K :O,$/g+t.9)u1 CB) 3% 5 ° ‘ lidfiéms ’ Marl-“(wté D) It can't be done, the cockroach is just to fast. t i E) 9.81mis2 X :1”; m \ ‘2 C Kl): VDO‘t k éqo X‘D fiUDGI‘E ‘2 g WWI... _______ _____*____ :2 Ox 2; g, O‘i w/s )(c :2 Vat ck t Version 1 Page 6 {Eisec 1].. A 4-kg block and a 2-kg block can move on the horizontal frictionless surface. The blocks are accelerated by a +12—N force that pushes the larger block against the smaller one. Determine the force that the 2-kg block exerts on the 4-kg block. +12N .. o- _. = . C\ “3 (:39 2 Em '— ‘Q‘ N ékj A) UN q = t; “4/31 Bl... . o . D :2N #54}. E) —4N a - _ __ _. ,1 H Canal 2 F "‘ Q‘Gl’fil' ‘\ e ‘W 12. A 0.75-kg ball is attached to a 1.0-m rope and whirled in a vertical circle. The rope will break when the tension exceeds 450 N. What is the maximum speed the ball can have at the bottom of the circle Without breaking the r0p e? A) 32 mis B) 16 1113’s E) 12 Infs \LW v r— : (“F-ng) if] m W 3&4w/s E Wok“ Hj<¢ so Lilo“ GM Version 1 Page 7 Use the following to answer question 13: Two vectors, A and B, are added together to form the vector C = A + B. The relationship between the magnitudes of these vectors is given by: C,f ='- O Cy = A sin 60" + 8 sin 30° AX and A}, point in the positive x and y directions, reSpectively. 13. H e magnitude of A compare with that of B? A A = 1.7Bi""\ .B) A = 0‘ 8. < C A=O.7’B £31423 BC¢J5EO ’3 Accfiéo E)A=0.SB _ (0330 Ezra; __ _ . ’4‘ B cosso‘ mar “BER/[’13 14. A particle moves along the x axis according to the equation x = 612 where x is in meters and t is in seconds. Therefore: A) each second the velocity of the particle changes by 9.8 mi’s B) the particle follows a parabolic path C) the acceleration of the particle is 6 mfs2 I cannot be negative E) none ofthe a UV L‘rf f if 5 fire ffivfl, X «‘7 {g ‘ [ta-Q Version 1 Page 8 15. A boat is traveling upstream at 14 mph with respect to a river that is flowing at 6 mph (with respect to the ground). A man runs directly across the boat, from one side to the other, at 6 mph (with respect to the boat). The speed of the man with respect to the E . A 131% w . B) Umq’t) lacfitT an ‘0 LHPLI C) 18.5mph D) 21 mph € E) 26mph V r: «(all 7 .. 17“ ~17 ife - < "3 “(‘3 ‘— fl'cl ‘3er M Pea “WEE—£53: 2 {Crow/of? v/ z "germ- Ae .. a fig Ur; = la 1. =— 399,01, “{9} -'" V *V w ~> "3 Wt": F “(B W 16. An 80 kg circus clown plans to climb a rcpe as part ofa comedy routine. The clown starts at rest on the ground next to a 60 kg box full of coconut cream pie. The rcpe goes over a pulley that is three meters above the ground. The other end of the rope is attached to the box of pie. What acceleration must the clown have to guarantee that the honofpiennu reach the pulley 1 second after he begins climbing? a]? agree) ) "91'81mrs2 C) 1.00 m/s2 D) 0.00 m2 E) 3.17m2 Version] Page9 Tr q 8 N _. —.2 17' If‘A+B 2A2+BZ,then: A) an le between 2 and E must be 60"- B) either 2 or B must'be zer ) :4 and 8 must be parallel and in the same direction D) :4 and 3 must be arallel and in opposite directions E) none of the above is true - _ q f( 2 74 I5 Ker-f {-LQ 18. An airplane pilot wishes to fly due west relative to the ground. A wind 0f74.0 kmfh is blowing toward the south. If the airspeed of the plane (its speed in still air) is 320.0 kmfh then what is the speed of the plane relative to the ground? A) 328 km/hr B) 2461(me _,_> .__\> c)___.32.0k1mm V :- U -— U _ é 3 I” ' bee/flue Him? at? [£679 N t . ' “9 *CJ Cirif‘ +0 $16 Version 1 Page 10 19. The diagram represents the straight line motion of a car. Which of the following statements is true? ‘ Cl 0 {<32 Wf vim-‘5} l S 12 — — , ‘ ‘ ( n Farsi o Nlouf a (£3. attract Waltz as) ' 5 9' C or we.) Ai The car accelerates, stops, an es he car accelerates at 6 mi’s2 for the list 2 s The car is moving for a total time of 12 s D) The car decelerates at 12 Ini’s2 for the last 4 s Q 3 H I 3 L) E) The car returns to its starting point when t = 9 s C-qu CCU VIP-Unfit“ “10.45 {0 w ' ‘ . Use the following to answer question 20: 0” Go I I! S Slé’v 74' /O(;‘f f 3 Two S-N boxes are attached to opposite ends of a Spring scale and suSpended from pulleys as shown. 599(Q MSG/‘63 {TC/(9’5? defle'o ,9 20. Suppose that the system were placed in an elevator that accelerated downward at 2 mfsz. What would the scale read? A) 2N B) ON C) 6N D) 8N ~_____M____../ Version 1 Page 1] ...
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p140w09_mid1_solutions - Physics 140 Winter 2009: Exam #1...

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