1 Exam I vers 0001 Physics 1120 Fall 2007 NAME print please Student ID TA s Name Circle one Edwin Widjonarko Craig Hogle Mike Mullan Mike Hermele Naresh Sen Starting time of your Tues recitation write time in box 9am noon 1pm etc Please do not open the exam until you are told to Your exam should have 12 pages numbered 1 thru 12 This exam consists of 18 multiple choice questions worth 75 points total and two multipart long answer questions worth 25 points total Fill in the bubble sheet with a 2 pencil PLEASE follow all directions carefully if you don t we may not be able to identify your exam which would be a disaster for you Place a check in each box on the left as you complete the instructions Circle your TA s name above Print and bubble in your name on the bubble sheet Print and bubble in your student Identification Number Print and bubble in your Exam version 0001 or 0002 in the upper left of your bubble sheet in the area marked 1234 Erase mistakes as thoroughly as possible Ask for a fresh bubble sheet if you fear you cannot thoroughly erase mistakes After you begin be sure to neatly print your name and ID on the long answer question pages At the end of the exam check that you have filled in the first 18 questions on the bubble sheet with only one bubble filled in for each question I have read and followed the instructions above Signature Vers 0001 2 1 A small positive test charge q flies by a large positive unmovable charge Q along the trajectory shown How do the magnitudes of the acceleration at points A B and C which we denote as aA aB aC compare with each other A A aC aA aB B aA aB aC C aA aB aC D aC aA aB E aC aB aA q B Q C 2 The electric field throughout a region of space is given by the formula r E Axy i Bx j where x y are the coordinates of a point in space and A B are constants r What is E j A Axy B Bx2 C Bx D B E none of these 3 Three charges are placed as shown If released the charge at the bottom of the picture will initially start accelerating in what direction A left B right C up D down E the acceleration is zero Vers 0001 r Q r up Q Q right 3 4 A balloon of mass M has been positively charged so that its charge is Q and placed next to a vertical blackboard as shown The blackboard polarizes so the balloon sticks to it The friction coefficient between the balloon and the blackboard is and we will assume that the electric field created by the blackboard is uniform and directed towards the blackboard perpendicular to it What is the magnitude E of this electric field A E Q Mg B E Q Mg C E M gQ D E Mg Q E E Mg Q 5 Three positive charges are placed as shown If released which way will the charge q initially accelerate A right B left C the acceleration is zero D down E up Vers 0001 r 2r up 2Q q Q right 4 6 A point charge with mass m and positive charge q is suspended on a massless string in a uniform horizontal electric field of magnitude E The electric field is adjusted until the string makes a 45 degree angle with the vertical Assuming we know E and q find the mass of the object HINT draw a free body diagram E 45 m q A qE g B qE 2 g C g q E 2 D qE g 2 E None of these is correct 7 A uniformly charged insulating rod is bent in the shape of a semi circle of radius R The total charge on the rod is Q There are no other charges nearby What can you say about the magnitude E of the electric field at the center of the semi circle Q E R A E kQ R2 C E kQ R2 Vers 0001 B E Q R2 D Not enough information to decide 5 8 A uniformly charged rod with linear charge density is positioned vertically as shown so that the distance between its lower end and the origin is L What is the magnitude of the electric field dE at the origin O created just by a small piece of the rod of length dl located at a height H above the lower end of the rod A dE k dl H 2 L2 B dE k H 2 L2 C dE k y dl d H dl 3 H 2 L2 2 O L dl D dE k H 2 L2 2 E dE k dl H 2 L2 x L d E 3 9 Two boxes of unequal masses M1 and M2 have been placed on a flat frictionless surface some distance away from each other and given unequal positive charges Q1 and Q2 The first box is heavier than the second M1 M2 however the charge on the first box is smaller Q1 Q2 Which of the following statements are true M1 Q1 A Both boxes start accelerating and the first one M1 has bigger acceleration B Both boxes start accelerating and the second one M2 has bigger acceleration C The accelerations are equal and nonzero D Neither of the boxes accelerate E None of the above Vers 0001 M2 Q2 6 10 Two rigid rods with charges attached at the end are arranged as shown Do the rods repel each other attract each other or neither attract nor repel in answering this question neglect gravity and friction A attract B repel C Neither attract nor repel If released the rods will remain still D Neither attract nor repel If released the rods will nevertheless move E Impossible to tell from the information given Q Q Q Q 11 An electroscope like the one shown on the picture is negatively charged by touching it with a negative glass rod The electroscope leaves spread apart and the glass rod is removed Then a positively charged plastic rode is brought closer to the top of the electroscope but it does not touch What happens to the leaves as the positive rod starts to approach A The leaves spread father apart B The leaves get closer together C One leaf moves higher the other lower D The leaves don t move Vers 0001 7 12 Two positive Q charges and one negative 2Q charge are placed as shown on the picture An electron of negative charge e is placed as shown Where is the force acting on the electron directed y A to the right positive x direction B upwards positive y direction C to the left negative x direction D downwards negative y direction E the force is zero Q 2Q 30 x 30 r Q electron 13 Two large parallel planes are shown edge on The …
View Full Document
Unlocking...