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Unformatted text preview: PHYSICS 222 Fall 2010 EXAM 1: September 30, 2010 8:00pm--10:00pm Name (printed): ______________________________________________________________________ Recitation Instructor: ________________________________________________ Section #_______ INSTRUCTIONS: This exam contains 25 multiplechoice questions, plus two extracredit 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 attached 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 ebook 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: 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 cell phone calls allowed. Either turn off your cell phone or leave it at home. Anyone answering (or using) a cell phone must hand in their work immediately; their exam is over. Best of luck, Paul Canfield and Paula Herrera Your last name, middle initial, and first name. Your ID number (the middle 9 digits on your ISU card) Special codes K to L are your recitation section. (Honors sections: H1 10 ; H2 23). Always use two digits (e.g. 01, 09, 11, 13) 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 = 1.01 105 Pa. (See formula sheet for densities). A. B. C. D. E. 2. A 2.00 kg sphere is made out of a plastic that has a density of 900 kg/m3. What minimum outer diameter does the sphere have to have so as to float on water? (The sphere can be hollow if necessary.) (See formula sheet for densities). A. B. C. D. E. It will always sink 7.82 cm 15.6 cm 24.3 cm It will always float 0.13 105 Pa 0.87 105 Pa 1.14 105 Pa 8.72 105 Pa 14.3 105 Pa 3. A Ushaped tube open on both sides contains water. Each arm has a 30cm high column of water in it. A 10cm column of oil (density 800 kg/m3) is added to one arm. How high is the column of water in the arm that has no oil added to it, when the system is in equilibrium? A. 28 cm B. 30 cm C. 32 cm D. 34 cm E. 36 cm 4. During a big storm a 60 km/h wind blows across the surface of a 2.00 m 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 B. 333 N pointed toward the outside of the house C. 3000 N pointed toward the inside of the house Inside of D. 3000 N pointed toward the outside of the house Wind house E. 0 N since the wind is along the plane of the window blowing Window 5. A large cylindrical container with a base radius of 10.0 m filled with water up to a level h = 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. A. 3.94 m/s B. 5.10 m/s C. 7.67 m/s D. 10.8 m/s E. 13.3 m/s 6.0 m 3.0 m 6. An inflated balloon with a total mass of 300g 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. A. 1.96 N B. 2.94 N C. 4.91 N D. 7.85 N E. 9.81 N 7. A 3.00g mass has a -4.00 C charge on it. If the mass is released, in vacuum, near the Earth's surface, what electric field is necessary to create a zero net force on the mass? A. B. C. D. E. 8. A metal bar has a cross section Ai and length Li. In this form, the bar has a resistance Ri. The whole bar is now reshaped into a wire with a cross sectional area of Af = Ai/1000, turning all the initial mass to fine wire. What is the resistance of the new long wire, in terms of Ri? A. B. C. D. E. 106 Ri 103 Ri Ri 10-3 Ri 10-6 Ri 7.35 N/C pointing up 7.35 103 N/C pointing up 7.35 103 N/C pointing down 7.35 106 N/C pointing up 7.35 x 106 N/C pointing down 9. A charge is placed at the origin of the coordinate systems shown below. The magnitude of the electrostatic force on the charge is greatest for: A B C D A. B. C. D. E. A B C D Same size force in each case. 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? Q R2 Q B. k 2 2R Q C. k 2 R Q D. 2k 2 R E. 0 A. k ^ j 11. A flat surface (10 cm 20 cm) is on the xz plane, in a uniform electric field E = 4000i + 3000 ^ . What is the magnitude of the electric flux through the surface? A. B. C. D. E. 60 Nm2/C 80 Nm2/C 100 Nm2/C 120 Nm2/C 150 Nm2/C 12. Which of the following statements about charges QA, QB, QC is consistent with the field lines shown below? B A C A. B. C. D. E. |QB| > |QA| > |QC|; QB is positive and QA and QC are negative |QB| > |QA| > |QC|; QB is negative and QA and QC are positive |QB| = |QA| = |QC|; QC is positive and QA and QB are negative |QB| < |QA| < |QC|; QC is positive and QA and QB are negative |QB| < |QA| < |QC|; QC 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 10-11 m. Let the dipole be centered on the origin of an xy plane and be in a uniform electric ^ field, E = 1000i N/C . What is the size and direction of the torque on the dipole? A. B. C. D. E. 14. Two charges Q1 = 3.00 C and Q2 = -5.00 C are fixed on the x axis at x1 = 0 and x2 = +2.00 m, respectively. At which point along the x axis (other than ) is the net electric field zero? A. x = -6.87 m B. x = -0.873 m C. x = +0.873 m D. x = +6.87 m E. There is no point along the x axis where the electric field is zero (except ). 6.40 10-27 Nm, out of the page. 6.40 10-27 ^ Nm i 2.19 10-27 Nm, into the page. i 2.19 10-27 ^ Nm None of the above. - 20 + 15. The plots I and II below are best associated with : A. I the electric field from a uniformly charged insulating sphere II the electric potential from a uniformly charged insulating sphere B. I the electric potential from a charged metallic sphere II the electric field from a charged metallic sphere C. I the electric potential from a charged metallic sphere II the electric field from a uniformly charged insulating sphere D. I the electric potential from a charged metallic sphere II the electric potential from a uniformly charged insulating sphere E. I the electric field from a charged metallic sphere II the electric field from a uniformly charged insulating sphere 16. A parallel plate capacitor has an area of 5.00 5.00 cm2 and a separation of 2.00 mm. When the space between the plates is empty, it has a capacitance, C*. A 1.00mm thick sheet of rubber ( = 3.00) with the same area is inserted into the void space (filling half of it). What is the new capacitance of the device in terms of C*? A. B. C. D. E. 17. Which of the following is necessarily true for a conductor in equilibrium? A. E = 0 inside, V = 0 everywhere. B. E = 0 inside, V = 0 on the surface. C. Any excess charge is all on the surface, the surface is an equipotential. D. Net electric flux outside the conductor is always zero. E. Electric field just outside the surface is parallel to the surface. C*/2 2C*/3 3C*/2 2C* 3C* The situation below pertains to the next two questions. A sphere of radius a = 2.0 cm with a uniformly distributed charge Q1 = 4.0 C is at the center of a conducting spherical shell of radii b = 4.0 cm and c = 6.0 cm that has a total charge Q2 = -8.0 C. B Q2 A C Q1 D 18. Find the electric field at point A, which is at r = 1.0 cm from the center of the system. A. 1.2 107 N/C B. 2.2 107 N/C C. 4.5 107 N/C D. 5.7 107 N/C E. 6.9 107 N/C 19. Compare the electric potentials at points A, B, C and D. A. VA > VB > VC > VD B. VA > VB = VC and VC < VD C. VA > VB = VC > VD D. VA < VB = VC and VC < VD E. VA < VB = VC and VC > VD 20. A point charge is placed near a neutral metal slab as shown below. + 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. B. The slab acquires a net charge by induction, and exerts a repulsive force on the point charge. C. The slab is polarized and exerts an attractive force on the point charge. D. 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. An infinite conducting slab with 8.85 nC/m2 on each of the two surfaces is perpendicular to the x axis and located between x = 0 and x = +1.0 cm (i.e., the thickness of the slab is 1.0 cm). The V = 20 V equipotential is at x = -1.0 cm. Find the potential at x = + 2.0 cm. A. 20 V B. 10 V C. 20 V D. 30 V E. 50 V 22. What is the net capacitance between points A and B? A. 1.0 F B. 2.4 F C. 4.2 F D. 8.3 F E. 11 F 23. Two spherical capacitors are connected as shown below: Battery 1 2 4 3 Let Qi and Vi (i = 1, 2, 3, 4) be the charge and potential of each of the spherical surfaces indicated in the figure. Which of the following is true? A. B. C. D. E. Q1 = Q3 ; V2 < V3 Q1 = -Q3 ; V2 = V3 Q1 = Q3 ; V4 > V3 Q1 = Q2 ; V4 = V1 Q1 = -Q4 ; V1 = V3 + 1.0 F A 3.0 F 2.0 F B 3.0 F 2.0 F 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? Sphere 2 Sphere 1 -Q - Q + A. The electric flux through the larger sphere is larger than the flux through the smaller sphere because the area is larger. B. The electric flux through the larger sphere is smaller because it is closer to the negative charge, which produces negative flux. C. The electric flux through both spheres is the same. D. Gauss's law does not apply here because of the absence of symmetry. E. The net flux through both surfaces is zero because the net charge is zero. 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 potential of a point located 2.00 m from their shared center? Take V() = 0 A. B. C. D. E. (10 C) k / (2 m) (15 C) k / (3 m) (20 C) k / (3 m) (20 C) k / (6 m) (35 C) k / (6 m) 26. The metallic object shown below has a negative charge. The points A and B are on surfaces of the 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. B A The electric field just to the right of point B is: A. B. C. D. E. 27. Four identical charges Q = 1.0 nC are on the corners of an square of side a = 3.0 cm. A fifth charge 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? + Q Q + A. 32 mm/s B. C. D. E. 52 mm/s 98 mm/s 110 mm/s 130 mm/s + q 9 N/C pointing to the right 9 N/C pointing to the left 14 N/C pointing to the left 49 N/C pointing to the right 49 N/C pointing to the left Q + + Q You may record your answers on this page and take it with you after the exam to compare to the posted solutions. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 ...
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- Fall '05