Physics 102 Exam 1 Fall Last Name: First Name Network-ID

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1 Physics Exam Fall 4 Last Name: First Name Network-ID Discussio Sectio: Discussio TA Name: Tur off your cell phoe ad put it out of sight. Keep your calculator o your ow desk. Calculators caot be share This is a closed book exam. You have iety (9) miutes to complete it.. Use a # pecil. Do ot use a mechaical pecil or pe. Darke each circle completely, but stay withi the boudary. If you decide to chage a aswer, erase vigorously; the scaer sometimes registers icompletely erased marks as iteded aswers; this ca adversely affect your grad Light marks or marks extedig outside the circle may be read improperly by the scaer. Be especially careful that your mark covers the ceter of its circl. You may fid the versio of this Exam Booklet at the top of page. Mark the versio circle i the TEST FORM box ear the middle of your aswer sheet. DO THIS NOW! 3. Prit your NETWORK ID i the desigated spaces at the right side of the aswer sheet, startig i the left most colum, the mark the correspodig circle below each character. If there is a letter "o" i your NetID, be sure to mark the "o" circle ad ot the circle for the digit zero. If ad oly if there is a hyphe "-" i your NetID, mark the hyphe circle at the bottom of the colum. Whe you have fiished markig the circles correspodig to your NetID, check particularly that you have ot marked two circles i ay oe of the colums. 4. Prit YOUR LAST NAME i the desigated spaces at the left side of the aswer sheet, the mark the correspodig circle below each letter. Do the same for your FIRST NAME INITIAL. 5. Prit your UIN# i the STUDENT NUMBER desigated spaces ad mark the correspodig circles. You eed ot write i or mark the circles i the SECTION box. 6. Sig your ame (DO NOT PRINT) o the STUDENT SIGNATURE li 7. O the SECTION lie, prit your DISCUSSION SECTION. You eed ot fill i the COURSE or INSTRUCTOR lies. Before startig work, check to make sure that your test booklet is complet You should have umbered pages plus three (3) Formula Sheets followig these istructios. Academic Itegrity Givig assistace to or receivig assistace from aother studet or usig uauthorized materials durig a Uiversity Examiatio ca be grouds for discipliary actio, up to ad icludig dismissal from the Uiversity. of pages (5 problems)

2 Physics A Exam Fall 4 This Exam Booklet is Versio A. Mark the A circle i the TEST FORM box ear the middle of your aswer sheet. DO THIS NOW! Exam Gradig Policy The exam is worth a total of 6 poits, composed of three types of questios. MC5: multiple-choice-five-aswer questios, each worth 6 poits. Partial credit will be grated as follows. (a) If you mark oly oe aswer ad it is the correct aswer, you ear 6 poits. (b) If you mark two aswers, oe of which is the correct aswer, you ear 3 poits. (c) If you mark three aswers, oe of which is the correct aswer, you ear poits. (d) If you mark o aswers, or more tha three, you ear poits. MC3: multiple-choice-three-aswer questios, each worth 3 poits. No partial credit. (a) If you mark oly oe aswer ad it is the correct aswer, you ear 3 poits. (b) If you mark a wrog aswer or o aswers, you ear poits. MC: multiple-choice-two-aswer questios, each worth poits. No partial credit. (a) If you mark oly oe aswer ad it is the correct aswer, you ear poits. (b) If you mark the wrog aswer or either aswer, you ear poits. Some helpful iformatio: A remider about prefixes: p (pico) = - ; (ao) = -9 ; (micro) = -6 ; m (milli) = -3 ; k (kilo) = +3 ; M or Meg (mega) = +6 ; G or Gig (giga) = +9. of pages (5 problems)

3 PHYS Exams FALL 4 Exam (A) September 4 The ext two questios pertai to the situatio described below. Two charges Q ad Q are placed o the x-axis, at x = ad x = cm, respectively, as show i the figur The charge Q = 5.5 µc, whereas Q is ot kow. A third charge q = +4.5 µc is placed a distace x = 3 cm from the origi, o the x-axis. ) What must the value of Q be such that the force o q due to charges ad is zero? Q = -5 µc Q = 7 µc Q = 5 µc Q = -7 µc Q = -5.6 µc ) Does your aswer chage if charge q is ow egative? No Yes of

4 The ext two questios pertai to the situatio described below. Cosider the cofiguratio of charges show: q = - C, q = -3 C, ad q 3 = +4 C. The grid is cm o a sid 3) Which of the followig vectors best represets the directio of the total force F 3,tot o charge q 3 due to q ad q? Figure C Figure D Figure E Figure B Figure A 4) Calculate the magitude of the total force F 3,tot o charge q 3 due to q ad q. F 3,tot = 6 µn F 3,tot = 5 µn F 3,tot = µn F 3,tot = 63 µn F 3,tot = 93 µn of

5 The ext two questios pertai to the situatio described below. A positively charged rod is brought close but does ot touch a ucharged coductig sphere (as show i steps a-b below). As a rod approaches, the sphere is coected to groud by a coductig wire (c). The groudig wire ad rod are the removed (d-e). 5) What is the charge o the coductig sphere after the sequece of steps? Zero Positive Negative 6) Now the sequece of steps is repeated, startig with the same coductig sphere (ucharged), but without groudig the spher What is the charge o the sphere after the sequece of steps (a-c)? Zero Negative Positive 3 of

6 The ext three questios pertai to the situatio described below. A electroscope is built by suspedig two idetically sized coductig spheres of mass m =. kg from thi wires of legth l = 5 cm as show i the figur After chargig, both spheres make a agle of θ = 5 relative to vertical ad Q = Q. (Note: i this problem, you may igore ay mass or charge from the thi wires.) 7) Because the system is i equilibrium: Gravity does ot act o the system. The spheres will experiece a et acceleratio. The spheres will ot experiece a et acceleratio. 8) If the charge of both Q ad Q is icreased, the agle θ will: decreas icreas stay the sam 9) What is the magitude of the charge Q? Q = C Q =.6-7 C Q = 5-8 C Q = C Q =.9-7 C 4 of

7 The ext three questios pertai to the situatio described below. Cosider the collectio of 4 charges below: ) Usig the field lies determie the correct orderig for the magitudes of the charges q3 < q < q < q4 q < q < q4 < q3 q3 < q < q < q4 q < q < q3 < q4 q < q3 < q < q4 ) Based o the ature of the field lies which of the followig is true: The sigs of q ad q are opposite of q3 ad q4. All of the charges have the same sig. The charges q ad q4 have the same sig. ) Whe placed at which poit will a test charge experiece the largest force? P R S 5 of

8 3) A sphere with charge +q is placed a distace d from a ucharged metal spher Of the four figures show, which figure best represets the resultig charge distributio o the metal sphere? Figure C Figure A Figure D Noe of these Figure B The ext two questios pertai to the situatio described below. A electric dipole has a separatio distace d = mm. It is placed cm from a fixed, positive charge q = 9.7 µc. 4) If δ =. µc what is the magitude of the et force o the dipole due to the sphere? F = N F = 87 N F =.8 N F =.44 N F = 4.3 N 5) The dipole is release I what directio will it travel? It will ot mov It will move away from the charged spher It will move toward the charged spher 6 of

9 The ext two questios pertai to the situatio described below. Give is a map of equal-potetial lies (see figure). The potetial is created by three charges i a plae (q, q, q 3 ). Potetial values are give i Volts. Note the sigs (+/-). Based o the map: 6) What is the sig (+/-) of the charge q? + - 7) How much total work W by you is required to move a charge of C from poit A to poit B, ad the from poit B to poit C? W = J W = 4 J W = - J W = J W = -4 J 7 of

10 8) You move two charges closer towards each other by equal distaces, util they are separated by a small distace They have equal masses ad charges of equal magitude ad opposite sig, Q ad -Q. The charges are exposed to a uiform electric field E, as show i the diagram. Keepig i mid iteractios betwee the two objects, which statemet best describes the work doe by you o the system of charges? I am doig egative work o the system of charges. I am doig positive work o the system of charges. I am doig o work o the system of charges. 9) Choose the statemet that best describes the work doe by you o the system show. The objects have equal charge Q, ad the directio of electric field is vertical. I am doig positive work o the system of charges. I am doig egative work o the system of charges. I am doig o work o the system of charges. 8 of

11 ) Cosider the case of two idetical charges, with equal mass M =.7 kg ad equal charge Q = +6 C, i the absece of a exteral electric fiel The charges start at a ifiitely far distace apart, ad move i opposite directios directly towards oe aother, with velocities of +5 km/s ad -5 km/s, respectively. What is the closest distace d that the charges will get to oe aother? d = 87 m d = 58 m d = 3 m d = 5 km d = 9 km ) What is the chage i potetial eergy of a particle of charge +q that is brought from a distace of 3R to a distace of R from a particle of charge q? U = -kq /3R U = -kq /4R U = -kq /R U = kq /3R U = kq /3R ) Two.9 µc charges are held fixed at the positios show i the figur Note that both charges are positiv Calculate the chage i potetial eergy U(B)-U(A) of a. µc charge that is moved from A to B. Note that the ruler lies show i the figure are equally space U = -.4 J U = -.4 J U = J U =.4 J U =.4 J 9 of

12 The ext three questios pertai to the situatio described below. Four poit charges are equally spaced by a distace d = 4.69 mm at the corers of a square, as show i the figur Three of the charges are positive, with q =.9 µc, while oe is egative with charge q = -.9 µc. 3) What is the electric potetial at the ceter poit betwee the fixed charges? V = V V =.6 7 V V =. 7 V V = -. 7 V V =. 7 V 4) Cosiderig oly the three positive charges, which vector arrow show below best represets the directio of the electric field at the positio of the egative charge? Figure A Figure B Figure C Figure E Figure D 5) Cosiderig oly the three positive charges, what is the magitude of the electric field at the positio of the egative charge? E =.9 9 N/C E =.7 9 N/C E = N/C E =.78 9 N/C E =.8 9 N/C of

13 Physics Formula Sheet FA4 Kiematics ad mechaics: x x v t at v v at v v a x v F ma a c r p E tot K. E. P. E. K. E. mv p mv W F Fd cos θ m Electrostatics: kq q F r E F q kq kqq r U Poit charge: E r Electric dipole: p qd τ pe si θ cos Resistace: dip U V q WE U W you kq V r U pe θ V q L R I Physical resistace: R ρ I t A V P IV I R R S R R R R R Capacitace: Q κεa C Parallel plate capacitor: C, V Ed V d Q U C QV CV C P C C C C C dip R P C S Circuits: V I i Iout t / τ t / τ q( t) q ( e ) q( t) q e t / τ I( t) I e τ RC Magetism: mv F qvbsi θ r Fwire qvb si θ τloop NIAB si φ qb Magetic dipole: m NIA τ mb si φ U mb cos φ B wire μ I B sol μ I πr dip dip

14 Physics Formula Sheet FA4 Electromagetic iductio: ε N BAcos φ t BLv ε ε si ωt ωnab si ωt ω πf εbar ge max V V rms max I rms I max V V p s I I s p N N p s Electromagetic waves: c λ E cb f u E ε E u B B μ u f f I I cos θ c rms B u εerms Brms εerms S I uc μ μ Reflectio ad refractio: θr θ i si θ si θ d o d c v i f f R si θ c hi d m ho d θ d M θ f i o ear Iterferece ad diffractio: Double slit iterferece: Sigle-slit diffractio: Circular aperture: Thi film: δ or ) ( d si θ mλ d si θ ( m ) λ m,, wsi θ mλ m, Dsi θ. λ film δ ( or ) t δ ( or ) δ m m m,, λ Quatum mechaics: E hf hc λ Blackbody radiatio: p x x Bohr atom: mke Z T λ max h λ p m K Photoelectric effect: K. E. hf W h π πr λ,,3 L mv r m) Z r (5.9 E 4 mk e Z Z (3.6eV )

15 Physics Formula Sheet FA4 7 (.97 m ) Z λ f i Quatum atom: L ( ) L z Nuclear physics ad radioactive decay: m 5 A Z N r (. m) A N t λn / 3 λt t T/ N( t) Ne N T E mc l.693 λ λ / Costats ad uit coversios: 9 g 9.8m / s e.6 C 9 7 ε 8.85 C / Nm k 8.99 Nm / C μ 4π T m/ A 4πε 8 c 3 m / s h 6.66 J s hc 4 mev ε μ 9 7 ev.6 J m proto.67 kg 938MeV 34 3 m electro 9. kg 5keV SI Prefixes Power Prefix Symbol 9 giga G 6 mega M 3 kilo k 3 milli m 6 micro μ 9 ao pico p