Physics 1111 Exam 1 2 30 C Solutions 8 February 2019 Name Physics 1111 Exam 1 2 30 C Solutions Instructions This is a closed book closed notes exam You will be given a separate sheet of formulas and numerical data that you may consult Nothing written on the formula sheet will be graded There is space after each question to show your work if you need more space you may use the back of the page or request more paper Please clearly indicate where your work for each problem is Underline or draw a box around your final answer The exam consists of five sections I recommend that you read all the questions at the start so that you can allocate your time wisely 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 PDAs or any other electronic devices besides calculators is forbidden All such gadgets must be turned off and put away throughout the exam Do not open the exam until told to begin You have one class period 50 minutes to finish the exam Make sure every page of the exam has your last name You must provide explanations and or show work legibly to receive full credit for Parts III V Make sure that your answers include appropriate units and significant digits Assume that air resistance is negligible unless otherwise stated 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 s standards of academic honesty for this exam and will not tolerate any violations of these standards by others Unsigned exams will not be graded Signature UGA ID 81x Row Seat Copyright c 2019 University of Georgia Unauthorized duplication or distribution prohibited Physics 1111 Exam 1 2 30 C Solutions 8 February 2019 Part I Score 12 II 27 III 40 Last Name IV B 21 Total Score 100 Grade 100 I Multiple Choice Questions 12 points For each question below choose the single best response and write the corresponding capital letter in the box provided There is no penalty for guessing 1 Marie wants to kayak across a river The current flows from north to south at speed v and Marie can paddle at a speed 2v in still water In what general direction should she head to cross the river to the east bank in the least amount of time B A B C D North of East Due East South of East The three directions take the same amount of time 2 A kicker kicks a football from ground level at the 10 yard line to the 50 yard line Where along the trajectory is the football s speed a minimum C A B C D E F At the 50 yard line just before the football lands At the 40 yard line At the 30 yard line At the 20 yard line At the 10 yard line just after the football leaves the kicker s foot The speed is the same throughout 3 A car s brakes produce a constant magnitude acceleration For some initial speed the stopping distance of the car is d If the initial speed doubles what will be the new stopping distance D A B C D E d 2 d 2d 4d 8d Copyright c 2019 University of Georgia 2 Physics 1111 Exam 1 2 30 C Solutions 8 February 2019 Last Name II Order Choice Questions 27 points For each question below write your responses in capital letters in the space provided 1 Each of the graphs below shows position velocity or acceleration plotted versus time for an object in motion along a straight line A B C v x a t t D t E x F a v t t t In the space provided identify in capital letters all graphs meeting the stated condition Write none if no graphs satisfy the condition a Velocity is constant A F b Acceleration is constant A B E F c Total displacement is zero over the time interval shown B d Velocity reverses direction B e Velocity increases over the whole time interval shown 2 Four projectiles are launched with different initial speeds so that they reach the same maximum height as shown Rank the trajectories in order of increasing initial speed Be sure to note if any of the initial speeds are equal Use less than symbols and equals signs to indicate rankings C E A B C D x B C D A Copyright c 2019 University of Georgia 3 Physics 1111 Exam 1 2 30 C Solutions 8 February 2019 Last Name III Table Slide 40 points Abby shoves her physics textbook horizontally from the left end of a long table with an initial speed of v0 6 20 m s The book then slides the length of the table and shoots off the right end with speed v1 5 10 m s landing on the floor a distance d to the right of the table The table is 2 80 m long and h 0 950 m high v0 v1 a What was the acceleration magnitude and direction of the book as it slid the length of the table 8 points The first two parts of this problem are 1 D motion There are two events to consider for this part of the motion the moment the book is given its initial velocity and the moment it leaves the table Let s call them Event 0 and Event 1 respectively As usual a table can be useful here Let s take the origin to be the starting point and the direction of motion right as positive t x vx ax Event 0 Event 1 t0 0 s t1 x0 0 m x1 2 80 m v0x 6 20 m s v1x 5 10 m s ax v12 v02 2a a The most direct way to find the acceleration would be to use the kinematic equation 2 2 2ax x Using the appropriate vfx vix quantities here gives v12 v02 5 10 m s 2 6 20 m s 2 2 21964 m s2 2 22 m s2 2 2 2 80 m The negative sign means that the acceleration is to the left If you chose to find time first then v1 v0 at1 would be a convenient way to find acceleration b How long did it take for the book to reach the far end of the table 7 points We have lots of options for this part particularly if we have found acceleration in Part a However we can find time without acceleration 1 2 2 2 80 m s v0 v1 t1 t1 0 495575 s 0 496 s 2 v0 v1 6 20 m s 5 10 m s If we already have a another option would be to use v1 v0 at1 Yet another option would be to use x vi t 12 at2 This requires solving a quadratic which will give us …