9/20/21, 11:10 AM Quiz: Exam #1 Exam #1 Started: Sep 20 at 11:10am Quiz Instructions This exam is “take home” and “open book", with the following constraints: You may use the content provided by me on the PHYS 4B Canvas page, including Textbook, “Physics for Scientists and Engineers, 4th Edition” Calculator either TI-83, TI-84, or one approved by the instructor (your phone does not qualify as a calculator!) Quizzes, discussions, assigned homework problems, and submitted assignments that you have personally worked out module videos and activities, and your own personal notes made on the above materials You may not: speak to anyone during the exam, except the instructor use any internet site that is not our WVC Physics Course page use the PhET virtual lab site look up, refer to, or use any source or material that has not been specifically approved by the instructor receive help from any one in any way, except the instructor use anything that I have not personally approved or provided This is a timed exam. The exam will open by 11:10 AM on Monday, September 20, 2021, after which you will have 80 minutes to complete it and upload your work and answers. The time starts as soon as you open the exam and will not be paused, even if you navigate away from the exam. If 80 minutes have elapsed, Canvas will automatically submit your exam for you, whether you are finished or not, so be sure to complete your exam and upload your work before 80 minutes have passed, or 12:30 PM, whichever comes first. Your exam must be uploaded as a pdf file within 80 minutes and no later than 12:30 PM on Monday, September 20, 2021. You must remain logged into Zoom while you are taking the exam. Please name your exam “exam1.pdf”. By taking this exam, you agree to the following statement: I understand that I may only discuss this exam with my instructor. I will use only my calculator, textbook, lecture notes, class videos, and homework problems that I have personally worked out and solved. I will not use any other resource unless I have received approval from the instructor, and I confirm that the work I submit is my own. I further understand that any violations of these rules will mean that I may receive a “0” for this exam. https://wvm.instructure.com/courses/44535/quizzes/221761/take 1/11 9/20/21, 11:10 AM Quiz: Exam #1 Qualitative Questions (15 points) Indicate the most correct choice for each of the following questions. Question 1 1 pts Two charged particles held close to each other are released. As they move, the force on each particle decreases. Therefore, the particles have the same sign. opposite signs. not enough information given. No answer text provided. Question 2 1 pts Two charged particles held close to each other are released. As they move, the force on each particle increases. Therefore, the particles have the same sign. opposite signs. not enough information given. No answer text provided. Question 3 1 pts If you comb your hair and the comb becomes positively charged, then your hair becomes https://wvm.instructure.com/courses/44535/quizzes/221761/take 2/11 9/20/21, 11:10 AM Quiz: Exam #1 uncharged. negatively charged. positively charged. No answer text provided. Question 4 1 pts How can a charged object attract an uncharged object made of a non-conducting material? The uncharged object must somehow gain a like charge. The uncharged object must somehow gain an unlike charge. The charges in the uncharged object can become polarized. Attraction of an insulator is not possible. Question 5 1 pts An uncharged conductor is supported by an insulating stand. You pass a positively charged rod near the left end of the conductor, but do not touch it. The right end of the conductor will be negative. positive. neutral. attracted. Question 6 https://wvm.instructure.com/courses/44535/quizzes/221761/take 1 pts 3/11 9/20/21, 11:10 AM Quiz: Exam #1 If two point charges exert a force of 1 N on each other when they are 3 cm apart, they will exert a force of 1/25 N when they are 15 cm apart. True False Question 7 1 pts Two unequal point charges q1 and q2 are held in place separated from each other. A point charge Q is placed somewhere on the line between them at a point where it remains stationary when released. From this observation, we can conclude that q1 and q2 must have opposite signs. True False Question 8 1 pts If two large objects are electrically attracted to each other, both objects must be negatively charged. both objects must be positively charged. one object must be negatively charged, and the other object must be positively charged. none of the above statements are absolutely true. Question 9 https://wvm.instructure.com/courses/44535/quizzes/221761/take 1 pts 4/11 9/20/21, 11:10 AM Quiz: Exam #1 Two charged particles attract each other with a force of magnitude F acting on each. If the charge of one is doubled and the distance separating the particles is also doubled, the force acting on each of the two particles has magnitude F/2 F/4 F 2F Question 10 1 pts The direction of an electric field is the direction of the force that the field would exert on a neutral test charge. an electron. an atom. a molecule. a positive charge Question 11 1 pts This figure shows the electric field lines in a region of space. Rank in order, from largest to smallest, the electric field magnitudes E1 to E4 at points 1 to 4. Explain your answer. https://wvm.instructure.com/courses/44535/quizzes/221761/take 5/11 9/20/21, 11:10 AM Quiz: Exam #1 1>2>3>4 1>2>3=4 4>3>2>1 4=3>2>1 none of the above Question 12 1 pts In the following figure, positive point charges q and 4q are located at x = d and x = 4d, respectively. Put points 1 to 3 in order of the magnitude of the net electric field, from largest to smallest: 1>2>3 3>2>1 3>2=1 3>1>2 none of the above. https://wvm.instructure.com/courses/44535/quizzes/221761/take 6/11 9/20/21, 11:10 AM Quiz: Exam #1 Question 13 1 pts A dust particle contains an excess of ten electrons. If this particle, when placed in an electric field accelerates to the left, we can conclude that the electric field must be pointing to the left. True False Question 14 1 pts If the electric field strength is 900 N/C at a point 5 cm from an infinite plane of charge, its strength will be reduced to 90 N/C at a point 50 cm from the plane. True False Question 15 1 pts An electron is initially moving in the positive x-direction when it enters a uniform electric field that points in the positive y-direction. The path the electron will take will be unaffected. be parallel to the y-axis. gradually curve upward and away from the x-axis and in the positive y-direction. gradually curve downward and away from the x-axis and in the negative y-direction. be a straight line. https://wvm.instructure.com/courses/44535/quizzes/221761/take 7/11 9/20/21, 11:10 AM Quiz: Exam #1 Quantitative Problems (60 points) Work out your answers on your own sheets of paper. Use a pencil or pen, write legibly and neatly, and clearly show your work, including any unclear steps. Work each problem in order, vertically down your sheet of paper. Just be sure that your work is legible, easy to read, and any mistakes you make is clearly indicated by placing a line through it. Start each new Quantitative Problem on a new side of paper. (Only one problem per side!) Number each page and place a box around your final answer(s). Express each answer using the correct number of significant figures. Place a BOX around each of your final answers. Once you finish working your problems, either scan or take pictures of your work, then save it as a single pdf document titled “exam1.pdf”. Remember, you will earn more points by solving each problem completely algebraically using variables only before plugging in numbers! Here are some constants you may find useful: k = 8.99 × 109 N∙m2/C2 g = 9.80 m/s2 e = 1.602 × 10–19 C m e = 9.109 × 10–31 kg m p = 1.673 × 10–27 kg Question 17 (20 points) https://wvm.instructure.com/courses/44535/quizzes/221761/take 8/11 9/20/21, 11:10 AM Quiz: Exam #1 Two small spheres carry charges q1and q2 and are attached to two light strings, as shown. One end of each string is attached to a fixed point, while the other end is attached to one of the charges. q1 is negatively charged and is placed a distance d directly above q2, which is positively charged. The mass of q1 is m 1 and the mass of q2 is m 2. A. (18 points) If gravity acts on each sphere, what is the tension in the lower string? Express your answer in terms of the given variables k, q1, q2, m 1, m 2, g, and d, as needed. B. (2 points) What is the tension in the lower string if q1 = −3.0 μC q2 = +3.0 μC, m 1 = m 2 = 40.0 g, g = 9.80 m/s2, and d = 15 cm. Question 18 (20 points) At one point above Earth’s surface a uniform electric field points straight up with a magnitude of 53 N/C. A small charged 10.0 mg bead is held stationary 1.0 m above the ground. What is the charge on the bead if it has an initial upward acceleration of 29.4 m/s2 when it is released from rest? Question 19 (20 points) https://wvm.instructure.com/courses/44535/quizzes/221761/take 9/11 9/20/21, 11:10 AM Quiz: Exam #1 A 10.0 cm diameter ring is uniformly charged to −20.0 nC. The center of the ring is located 20.0 cm from the center of a 10.0 cm long, thin rod. The rod is uniformly charged to +20.0 nC. What is the magnitude and direction of the net electric force acting on a proton located at the midpoint between the ring and the rod? Assume that the ring lies in a plane that is perpendicular to a line drawn from the ring’s center to the center of the rod. Question 16 60 pts Work out your solutions to the above Quantitative Questions, then save your work and upload it to Canvas as a pdf file using the button below. BEFORE SUBMITTING YOUR WORK... Did you show all your work? Unsupported answers will not receive credit. Is your work easy to read as a pdf? Double-check! After saving your work to a pdf, be sure to open it to make sure that it is very clear and legible and that any pictures you have taken are sharply in focus. Don’t forget to upload your exam as a single “pdf” file for the “Exam 1” assignment on Canvas. Name your file using the following format: exam1.pdf. Upload Choose a File https://wvm.instructure.com/courses/44535/quizzes/221761/take 10/11 9/20/21, 11:10 AM Quiz: Exam #1 Not saved https://wvm.instructure.com/courses/44535/quizzes/221761/take Submit Quiz 11/11
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