Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Physics 1112 Spring 2010 University of Georgia Instructor: HBSchüttler PHYS 1112 In-Class Exam #2A Thu. March 18, 2010, 9:30am-10:45am This is a closed-book, closed-notes exam, but you are permitted to bring and use a copy of the official Formula Sheet for this exam, which you should have printed out from the PHYS1112 web page. The exam consists of 12 multiple-choice questions. Each question is worth one raw score point. There will be no penalty for wrong answers. No partial credit will be given. I recommend that you read all the questions at the start so that you can allocate your time wisely. (Answer the easy questions first!) You may use a scientific calculator for arithmetic only; your calculator must be non-graphing, non-programmable, and non-algebraic. You are not allowed to share your calculator. The use of cell phones, pagers, PDAs, or any other electronic devices (besides calculators) is forbidden. All such gadgets must be turned off and put away; distractions caused by these devices will not be tolerated. • Do not open the exam until you are told to begin. • Make sure the scantron sheet has your name and your UGA Card ID (810-...) number filled in. Make sure you also have entered your name, UGA Card ID number and signature on the exam cover page (this page!) below. • At the end of the exam period you must hand in both your scantron sheet and this exam cover page, signed and with your name and UGA Card ID (810-...) number filled-in. You may keep all other pages (pages 3+) of this exam paper. • Your exam will not be graded, and you will receive a score of zero, if you do not hand in both a properly filled in scantron sheet and this properly filled-in and signed exam cover page. • You have until the end of the class period (i.e. until 10:45am for Period 2 Class, until 12:15pm for Period 3 Class) to finish the exam and hand in the required exam materials described above. By signing below, you indicate that you understand the instructions for this exam and agree to abide by them. You also certify that you will personally uphold the university standards of academic honesty for this exam, and will not tolerate any violations of these standards by others. Unsigned exams will not be graded. Name (please print): UGACard ID (810-...) #: Signature: 1 Physics 1112 Spring 2010 University of Georgia Instructor: HBSchüttler WORKSPACE 2 Physics 1112 Spring 2010 University of Georgia Instructor: HBSchüttler Conceptual Problems Problem 1: A beam of coherent (laser) light of wavelength λ is incident upon two parallel slits with spacing d, and with λ < d, as shown in the figure below. Assume |∆y| is the distance (in cm) between the two dark fringes (interference intensity minima), observed closest to the central maximum on a screen at a distance L on the other side of the doubleslits. This distance |∆y| will 1st dark fringes Fig. 2.04 Δy Screen θ L Double Slit Laser Beam (A) (B) (C) (D) (E) decrease if we decrease L (keeping λ and d fixed); decrease if we increase λ (keeping L and d fixed); decrease if we decrease d (keeping λ and L fixed); increase if we decrease λ (keeping L and d fixed); increase if we increase d (keeping λ and L fixed). Problem 2: If two point charges Q1 and Q2 at some distance r repel each other with a force of 10µN, what force would they exert on each other if Q1 is tripled (×3) without change of sign; r is doubled (×2), and the sign of Q2 is reversed ? The two charges will (A) (B) (C) (D) (E) attract each other with a force of 13.33µN attract each other with a force of 15µN repel each other with a force of 15µN repel each other with a force of 7.5µN attract each other with a force of 7.5µN Problem 3: In the figure below Q1 is a positive and Q2 is a negative point charge, |Q1 | and |Q2 | being of comparable magnitude. Which arrow drawn at P could correctly represent ~ generated by Q1 and Q2 at P ? the electric field vector E 3 Physics 1112 Spring 2010 University of Georgia Instructor: HBSchüttler Fig. 2.11 P (D) Q2 (E) (C) (A) (B) Q1 (A) (B) (C) (D) (E) Problem 4: In Experiment 1 an electron travels from point A to point B, in the electric ~ generated by/between two oppositely charged capacitor plates, as shown in the figure field E below. In Experiment 2 a proton travels from point A to point B, in the same electric field between the same two charged capacitor plates. A proton has a charge +e and an electron has a charge −e. Fig. 2.13 ------------------------E B A E +++++++++++++++++++++++++++ Assume the electron experiences a drop in electric potential, ∆V = −1500V, and a gain of potential energy, ∆U = +240aJ (where 1aJ ≡ 10−18 J), in traveling from A to B. What will the proton experience ? (A) (B) (C) (D) (E) ∆V ∆V ∆V ∆V ∆V = −50V and ∆U = −8aJ = −100V and ∆U = −16aJ = +100V and ∆U = +16aJ = −1500V and ∆U = −240aJ = +1500V and ∆U = +240aJ Numerical Problems Problem 5: If a diffraction grating is illuminated at normal incidence by coherent (laser) light it produces 3rd order maxima at angles of ±72.0o measured from the central (0th order) intensity maxium. At what angles θ, measured from the central (0th order) intensity maxium, will the 2nd order maxima be observed ? 4 Physics 1112 Spring 2010 (A) (B) (C) (D) (E) University of Georgia Instructor: HBSchüttler ±24.0o ±15.2o ±48.0o ±18.5o ±39.3o Problem 6: Two point charges lie on the x-axis: Q1 = +360µC is at x = 0, and Q2 is at x = 10.0cm. A third charge q will be in equilibrium when placed at x = 12.0cm. Therefore, Q2 is (A) (B) (C) (D) (E) +60µC +10µC −60µC −10µC −30µC Problem 7: Two point charges, spaced 112.4m apart, repel each other with a force of 140.0N. What is the amount of the smaller point charge if the larger charge is 3.5 times the smaller charge? (A) (B) (C) (D) (E) 3.5mC 5.5mC 7.5mC 9.5mC 26.3mC Problem 8: If a charge of +72µC is uniformly spread out over a single, very thin square of titanium sheet metal, of 4.0m sidelength, what is the strength and the direction of the electric field generated by that charge, very close to the surface and far from the edges of that sheet? ~ pointing away from the sheet (A) 9904. × 103 N/C, E ~ pointing away from the sheet (B) 254.2 × 103 N/C, E ~ pointing away from the sheet (C) 40.46 × 103 N/C, E ~ pointing towards the sheet (D) 9904. × 103 N/C, E ~ pointing towards the sheet (E) 40.46 × 103 N/C, E Problem 9: The total electric flux passing through the approximately spherical surface of a real, NBA-approved basket ball is Φ = −113Nm2 /C (assuming outward directed normal to the surface). What is the total electric charge enclosed inside the ball ? 5 Physics 1112 Spring 2010 (A) (B) (C) (D) (E) University of Georgia Instructor: HBSchüttler −1.00nC −0.60nC +0.80nC +0.40nC +2.20nC Problem 10: The 1500µF capacitor in a defibrillator is charged with a 200V battery. What is the charge stored on the positive plate of this capacitor ? (A) (B) (C) (D) (E) 100mC 300mC 500mC 700mC 900mC Problem 11: How much electric field energy is stored in the defibrillator capacitor in Problem 10 when it is fully charged ? (A) (B) (C) (D) (E) 20J 90J 60J 80J 30J Problem 12: If the electric field strength between the capacitor plates in Problem 4 is 2610.V/m, what is the magnitude and the direction of the proton’s acceleration ~a, assuming the proton is subject only to the electric force between the plates ? (A) (B) (C) (D) (E) 25.0 × 1010 m/s2 , ~a 25.0 × 1010 m/s2 , ~a 60.0 × 1010 m/s2 , ~a 60.0 × 1010 m/s2 , ~a 60.0 × 1010 m/s2 , ~a pointing pointing pointing pointing pointing rightward upward leftward upward rightward 6