Exam 1 solutions-2010

Exam 1 solutions-2010 - ' Sou/Tum $ - _ PHYSICS 222...

Info iconThis preview shows pages 1–16. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 10
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 12
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 14
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 16
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ' Sou/Tum $ - _ PHYSICS 222 "Fall 2010 EXAM 1: September 30, 2010 3:00pm—-10:00p'm Name (printed-l: Recitation instructor; Section ll ' INSTRUCTIONS: This exam contains 25 multiple-choice questions, plus two extra-credit questions, each worth 3 points. Choose one answer only for each question. Choose the best ansWer to each question. Answer all questions. Allowed material: Before turning over this page, put away all materials except for pencils, erasers, rulers and your calculator. There is a formula sheet attach-ed at the end of the exam. Other copies of the formula sheet are not allowed. Calculator: In general, any calculator, including calculators that perform graphing, is permitted. Electronic devices that can store large amounts of text, data or equations {like laptops, palmtops, pocket computers, PDA or e-book readers) are NOT permitted. if you are unsure whether or not your calculator is allowed for the exam, ask your TA. How to fill in the bubble sheet: Use a number 2 pencil. Do NOT use ink. if you did not bring a pencil, ask for one. Write and fill in the bubbles corresponding to: — Your last name, middle initial, and first name. ~ * * Your ID number (the middle 9 digits on yourlSU card! fir fir - Special codes K to L are your recitation section. (Honors sections: H1 9 10 ,' H2 9 23). Always use two digits (e.g. 01, 09, 11, 13) ' ' Please turn over your bubble sheet when you are not writing on it. if you need to change any entry, you must completely erase your previous entry. Also, circle your answers on this exam. Before handing in your exam, be sure that your answers on your bubble sheet are what you intend them to be. You may also copy down your answers on a piece of paper to take with you and compare with the posted anSWErs. You may use the table at the end of the exam for this. When you are finished with the exam, place all exam materials, including the bubble sheet, and the exam itself, into your folder and return the folder to your recitation instructor. No cellphone callsailowed. Either turn off your cell phone or leave it at home. Anyone answering (or using) a cell phone must hand in their Workimmediately; their exam is over. Best of luck, Poul Confieid and Paula Herrera 1. What is the absolute pressure (not gauge pressure) at the bottom of a beaker filled with mercury that is 10.0 cm deep? Take patm = 1.01 x 105 Pa. (See formula sheet for densities). A. 0.13 x 105 Pa 3. _ 0.87 x 105 Pa 1.14 x 105 Pa “0. 8.72 x 105 Pa E. 14.3 x 105 Pa 2. A 2.00 kg sphere is made out of a plastic that has a density of 900 kg/ma. What minimum outer diameter does the sphere have to have so as to float on. water? (The sphere can be hoilow if necessary.) (See formula sheet for densities). A. It will always sink 8. 7.82 cm C. 15.6 cm p. 24.3 cm It will always float 3. A U—shaped tube open on both sides contains water. Each arm has a 30-cm high column of water in ' it. A 10-cm column of oil (density 800 kg/rnB) is added to one arm. How high is the column of water in the arm that has no of! added to it, when the system is in equilibrium? A.. 28cm 13. 30 cm 4 z ._ I '. 32 cm ' . - . l m Al X. w lg “U f; (:7?) ‘M {V} 9 l M” m i- ; 4 , 3: ' k / 1‘ Vi] 4’ :3;- "5’ l r Cfl‘i /l “m, i 4. During a big storm a 60 km/h wind hiatus across the surface of a 2.00 m x 1.00 m window. What is the force on the window associated with this wind? (See formula sheet for densities). A. 333 N pointed toward the inside of the house 333 N. pointed toward the outside of the house C. 3000 N pointed toward the inside ofthe house D. 3000 N pointed toward the outside of the house Inside of Wind E' O N Since the Wind: is along the plane of the window house . . \ blOWIng l‘ e mo 1. “A +- C) = +— // Pal—Lu l l 2. l ( {V} f) . t l :3 l l r) ( 60 ,Cl . ...~ . 3 fl 2 r; N ' % 2—— 1 Z \ _.»’ “a 1'3 l Lip," i: ., A (Ti 61 (f .3 3%?) 3 cl tattle, 5. A large cylindrical container with a base radius of 10.0 m filled with water up to a level 11 = 6.00 m is being emptied with a siphon hose with a 10.0 cm diameter whose end is 3.00 m below the bottom of the container (see figure). Determine the speed of water as it exits the hose. 6.0 m A. 3.94 m/s B. 5.10 m/s C. 7.67 m/s 6. An inflated balloon with a total mass of BOO-g and a volume of 500 cm3 is attached to the bottom of a pool with a cable. The pool is filled with water, and the balloon is fully submerged. Find-the tension in the cable. 5A." 1.96N ..,._ . 2.94 N W . 2: "‘33 c 4.91 N i o 7.85 N l E 9.81 N = 7. A 3.00-g mass'has a —4.00 tLC charge on it. lfthe mass is released, in vacuum, near the Earth’s surface, what electric field is necessary to create a zero net force on the mass? ' ' ' ' T— A. 7.35 N/C pointing up V B. 7.35 x 103 N/C pointing up 7.35 x 103 N/C pointing down r“ o. 7.35 x 10“ N/C pointing up ‘- £3" E. 7.35 xx 10'5 MC pointing down . _ ' 8. A metal bar has a cross section A. and length Li. In this form, the bar has a resistance R5. The whole bar is now reshaped into a wire with a cross sectional. area ofAr = Ali/1000, turning aIE the initial mass to fine wire. What is the resistance of the new long wire, in terms of Re? 105 R] \ [ a M M (M "M r $31k .2: r173 W31. - ILX 7‘3 )ktqu-l r; I \f‘i‘vgfi 2‘ ‘ K i -: '\ ‘h—M” - W V m ‘ ' B. 103R; J“ "‘ ‘— c. R.- D. 10'3 R; t a - _ [ ,le T E. 10'6 R1 LL [ ‘L- " L" “F ,fi u 0 9. A charge is placed at the origin ofthe coordinate systems shown below. The magnitude_of_the electrostatic force on the charge is greatest for: 10. A half circular ring (radius R} made of a thin plastic rod has a total charge Q spread evenly over its length. What is the magnitude of the electric field at the center of the circle? , .jx (J . — a 3;”. 11. A flat surface (10 cm X 20 cm) is on the xz plane, in a uniform electric field E =(4000i +BOOOJ'). What is the magnitude of the electric flux through the Surface? p A 50 le/c . .. z _ «v B. so NmZ/C " c. 100 NmZ/C 7 v? .4; N .1» D. 120 Nmz/c r” —_ -. .A z (5 (:2. 61"“? , E 150 NmZ/C ~-~“'- C ./--, == l 5U l C} : $an A 3 "02m 12. Which of the following statements about charges GA, 03, Q: is consistent with the field lines shown beiow? [QB| :4 [QM > [Qc|; an is positive and QA and Q: are negative E. IQBI > IQAI > lad; QB is negative and QA and Qc are positive C. 1051: WA! '-‘ Ich: QC is positive and QA and on are negative D. ]QBE < |QA| < jacj; Q: is positive and QA and QB are negative E. |QB| < |QA| < lac]; Q: is negative and QA and QB are positive. 13'. A water molecule has a dipole moment equivalent to having a proton and an electron separated by 4.00 x 10'11 m. Let the dipole be centered on the origin of an xy plane and be in a uniform electric field, LE =1000i N/C . What is the size and direction of the torque on the dipole? A. 6.40 x 10‘27 Nm, out of the page. a. 6.40 x 10'27 f Nm C 2.19 x 10‘27 Nm, into the page. D 2.19 x 10‘27 iNm None of the above. T: ,7)” = 6.9%?)- ‘U i T, )4. \Ciw‘fK my} l 9‘ .- ' s ,i' 14. Two charges C21 = 3.00 C and Q; = —S.00 C are fixed. on the x axis at X; = 0 and x2 = +2.00. m, respectively. At which point along the x axis {other than ice) is the net electric field zero? x=—6.87 m B. X: —0.873 m C. x = +0873 m D. x = +6.87 m E. There is no point along the x axis where the electric field is zero (except :00). ‘_ _.,...m-n.a-2< “ESQ Al 79/ fell; L :7: (Hula .. ii 15. The plots I and il below are best associated with : Pint I Plot II A. l - the electric field from a uniformly charged insulating sphere il — the electric potential from a uniformly charged insulating sphere B. i» the electric potential from a charged metallic sphere ll ——the electric field from a charged metallic sphere .43 /‘< @l — the electric potential from a- charged metallic sphere- ” — the electric field from a uniformly charged insulating sphere D. l' - the electric potential from a charged metallic sphere II -the electric potential from a uniformly charged insulating sphere E. | - the electric field from a charged metallic sphere ll — the electric field from a uniformly charged insulating sphere Chair 3:. ; ( i" C) 1‘33“ 5- If u WI 7‘ H”? M' ‘~ . . ' I " gull—Eli 16. A parallei piate capacitor has an area of 5.00 x 5.00 cm2 and a separation of 2.00 mm.'- When the space between the plates. is. empty, it has a capacitance, C*. A LOO-mm thick sheet of rubber (g: 3.00) with the same area is inserted into the void space (filling half of it). What is the new I capacitance of the device in terms of C*? 2: FR“. olé ARM-as (as "E? 3c*/2 " " r- l » (BJ 29 7-1 , a. cycle {I “’7 EILQLD - i E. 30* C2,. ; 17. Which of the following is necessarily true for a conductor in equilibrium? A. E=0 inside,@everywhere.4 : Cl‘ i€,lf‘-§f%3 Us 9.- lS. .- 03 E: 0 inside, V: O on the surface. 9. c (-C/l-Any EXCESS Charge is all 0" the surface, the surface is an equipotential. 2 I V I 0. Net electric flux outside the conductor is always zero. ‘57—— O g. chug gm E- EIECtrlC “Eld lust DutSlde the surface is parallel to the surfaceffi W “ ((1313);; Css‘eclU c ..—-5) E? (Tilélifiiclii is; The situation below pertains to the next two questions. A sphere of radiusa = 2.0 cm with a- uniformly distributed charge 01 = 4.0 pC is at {hecehter bf a conducting spherical shell of radii b = 4.0 cm and c = 5.0 cm that has a total charge Q2 =I e81} LLC. 18. Find the electric field at point A, which is at r= 1.0 cm from the center of the system. _.W m] 1_ __ we. r; - . C L O A. 1.2x107N/C Qdesiu‘gfi gVLLQJ + r L a. 2.2 x 107 MC IL @45x107N/c 3 me E 3' __. _ r D. 5.7 x 107 N/C / M} E. 6.9 x 107 MC “‘3 ' flier “E 3 web , *mww— I; ,/- m fut an“ 19' compare the Elecmc Potentials at points A, B, C and D_ 3 O \ 1 "WW—WWW“: \, \ _____—_ —___._‘ .«j I I e; _ 9 _A. VA>VB>VC>VD ® VA>va=vcandvc<vo _ c 1/,e.>vfl=i/c>vD ' _.-~ D. VA<VE=VEand VC<VD E. VA < V8: V: and Vc > VD - ' i ~— 4 - € - {wig} LE‘hS .-- . 3‘ if $154.. V nwsi‘ deu’ewa-c in ‘ /«- 1V; 2]? ‘hfi—L E %I:-E. \ > VS; m- D D \‘jc’ 1‘ \r’ir: :7; $315; V : (“Em-g ‘ U53 (fl, C1” cm’h‘wu (15“) J f‘ x...“ v wt. Lu 20. A point charge is placed near a neutral metal slab-as shown beiow. @Q Which of the following is true? A. The slab acquires a net charge by induction, and exerts an attractive force on the point charge. The slab acquires a net charge by induction, and exerts a repulsiVE force on the point charge. The slab is polarized and exerts an attractive force on the point charge. The slab is polarized and exerts a repulsive force on the point charge. E. Nothing happens because the metal slab is neutral to begin with. (’21 21. An infinite conducting slab with 8.85 nC/mz on each of the two surfaces is perpendicular to the x axis and located between x = 0 and x = +1.0 crn' (i.e., the thickness of the slab is 1.0 cm). The V: 20 V equipotential is atx = —1.0 cm. Find the potentiai at x = + 2.0 cm. A. —20v 5. —10v 20v D. 30v E. 50v 22. What is. the net capacitance between points A and B? 1. l!) l: 0 lil: A. 1.0 pF 1 l i A B. 2.4 F '1 r2 : P 125‘ E 1M: 2‘ J2 (Hoe—ex...” i\ C- 4‘2 LIF ; [ 1§_J_,_....a—-\:d-—MO . .7 3 3 D" 8'3 “F ' 3.0 uF 2.0 ur E. i 11 “F 2.0 [1F c,» e” 9“ “g” S “Lt-"5197‘: ' - H PL- .1, l“, jl‘: +31:— l 1 :5 I?“ "‘ 23. Two spherical capacitors are connected as shown below: Battery Let Qiand V; U = 1, 2, 3, 4} be the charge and potential of each of the spherical surfaces indicated in. the figure. Which ofthe following is trUe? A- Q1 = 03 3 V2 < V3 I}; [YE {$31.2 Q1 = ‘03 I V2 = Va (:C.J}Q]_=Q§;V4>V3 *n/ ! _.4—~'-hu/v. D. Q1 = Q: ,' V4 : V1 pow—M-m-"d—Fmi """"""""" WM “‘2. E. Q1=—QAJV1=V3 ., a i— — it \il + 7; l'F i Z 3 Dr q l {in \x’? > V13 Ll 1.5;. J 4» to 24. Two charges Q and —Q are located in a region of space, far from other charges, as shown below Consider the two imaginary spherical surfaces indicated with dotted lines in the figure. Which of the following statements is correct? Spherez a‘- - — . _ _ hhfi“ 2" ‘H‘ l \‘ I” Sphere 1 x I ,"‘-“"- X 'I (I x ‘ , I “ \ r " \ l I I m i ' Q l 5 Q - - ® I . ® I “ I I “ \ I, ’f \ ‘\ ,’ r \ \‘ a I \ \_____a’ l \ l ‘4 I \ l x I A. The electric flux through the larger sphere is larger than the flux through the small-er sphere because the area is large r. ~:’_-—-- i}; 515k“ O.i33'xr:~s’tj"i"_ (Asian l J . I B. The electric flux through the larger sphere is smaller because it is closer to the negative charge, ', l i. = “ .p. s m "-T which produces negative flux. l liners: Kati a -— We c1..flr;a.l.lr_e§ 1;} bit 0:12»; are. \,l c; The electric flux through both spheres is the same. t?“ I _ Gauss's law does not apply here because of the absence of symmetry. 'ér" [flint-3' 1M3"? E. (The net flux through both surfaces is zero because the net charge is zero. c ’3'". 25. An insulating sphere with a uniformly distributed charge of 5.00 C has a radius of 1.00 m. A concentric, thin walled metallic shell has a charge of 10.0 C and a radius of 3.00 m. What is the electric potentiai of a point located 2.00 m from their shared center? Take V(°°) = 0 A. (10C)k/(2m) B. (lsclk/(Brn) c. (20C)k/(3.m) p. (20C)k/(6m) .2 QED (35C)k/(6m) 26. The metallic object shown below has a- negative charge. The points A and B- are on surfaces ofthe object that have spherical curvature with radii of 7.00 cm and 3.00 cm respectively. The magnitude of the electric field. just to the left of point A is 21 N/C. The electric field just to the right of point B is: 9 N/C pointing to the right 9 WC pointing to the left 14 [WE pointing to the left ' . 49 MC pointing to the right Egjags‘d 49 MC pointing to the left 00.61? m an. '2:— q = 5.0 nC is placed in the middle of one of the sides (see figure), All charges have a mass of 1.0 g. Charge q is released from rest from that position. What is the speed of charge q when it is very far from the square? A. 32 mm/s B. 52 mm/s C. 98 mm/s 110 mm/s 130 mm/s ...
View Full Document

This note was uploaded on 02/11/2012 for the course PHYSICS 222 taught by Professor Ogilvie during the Fall '05 term at Iowa State.

Page1 / 16

Exam 1 solutions-2010 - ' Sou/Tum $ - _ PHYSICS 222...

This preview shows document pages 1 - 16. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online