Keep This Page Attached to the ExamPhysics 1A Winter 2020 Final Exam Cover SheetINSTRUCTIONS:Right now, as soon as you get this part of the exam:1. Fill in this cover sheet completely (which you should have). You need to upload this page separately.2. Write your response to each problem on a separate paper.3. Count the pages of the exam. There should be 11 pages in total with probelms and questions on page 2 -9. If you find this is not the case, email me IMMEDIATELY. It is your responsibility to have a complete exam.Remember:* You are only allowed to consult your notes, homework, exams and textbook, and you are encouraged to doso during the exam. Do not try to search for an answer online. Follow all instructions. If you are asked tostart your response in a certain way, you have to follow it. For multiple choice questions, you have toexplain. In general, an answer without an explanation or steps shown will not receive any credit. *Don’t Cheat!We automatically report anyone suspected of cheating to Student Judicial Affairs.I certify by my signature below that I have read the above instructions and that I will abide by the UC Davis Codeof Academic Conduct. This includes· not copying from anyone else’s exam· not letting any other student copy from my exam· not collaborating with anyone· not consulting any unauthorized resource· not discussing this exam with any student who has not yet taken it, nor providing any information, written ororal, that might get to a student who has not yet taken itName (Print Clearly):Last FirstStudent ID:Signature:| | | | page 2Last Name First Name First three initials of last nameGrade:1. (5 points) Mary has written an equation describing the torque (τ ) on an object. However, one factor, (?), ismissing from the equation,τ = pa(?) ,where p is the magnitude of the momentum of the object, and a is the magnitude of the acceleration of theobject. In order to have the dimensions/units to work out, (?) has to be: (There is only one answer. Show allyour work to explain your answer.)I. t, the time since t = 0,II. d, diameter of the object, orIII. v, speed of the object.2. (5 points) A driver applies the brakes on a car traveling at 60.0 mph, which we will take it as 26.8 m/s. Thecar then stops after traveling for 40.0 m under such a constant acceleration. What is its speed when it hastraveled for 20.0 m after applying the brakes?26.8 m/s v = 020.0 m 20.0 mv = ?| | | | page 3Last Name First Name First three initials of last nameGrade:3. (5 points) Three identical rocks, rock X, rock Y, and rock Z are thrown with the same speed but in differentdirections as shown. If the effect from air resistance is negligible, determine if the following statements aretrue or false. Explain your choices.I. They all hit the ground at the same time. True / FalseII. They all hit the ground with the same speed. True / FalseIII. They all hit the ground with the same vertical component of their velocity. True / False4. (5 points) Two blocks of masses, m and M, sitting one on top of each other are placed on a smooth frictionlesstable as shown. However, the surface between m and M is not smooth. In a stunt, a person applies a force(F~A) on M towards the right such that M is removed from the table while m remains on the table althoughbeing slightly displaced. Draw two separate free body diagrams for m and M. Is the friction between m andM kinetic or static? Hint: Look at Problem 4 on midterm 1. What is the difference here?Free body diagram of m Free body diagram of MIs the friction between m and M kinetic or static? Briefly explain.| | | | page 4Last Name First Name First three initials of last nameGrade:5. (5 points) A person (mass = 70.0 kg) stands on an elevator which is acclerating upwards at 20.0 m/s2. Draw afree body diagram for the person and find the apparent weight he is experiencing. Hint: Look at L6.pdf aboutapparent weight.Free body diagram of the person6. (5 points) A player throws a basketball straight up at 5.0 m/s from 2.0 m above the ground. It only reaches ahighest height of 3.0 m above the ground, indicating there is a presence of air resistance. From the momentwhere the basketball leaves the player’s hand to the moment where the basketball is at the maximum height,state whether the following quantities are negative, positive, or zero. Explain all your choices. “∆” is definedas final minus initial.I. ∆KE, the change of kinetic energy of the basketball: negative / positive / zeroII. ∆P EG, the change of potential energy of the basketball and the Earth: negative / positive / zeroIII. WNC, the work done by non-conservative forces: negative / positive / zeroIV. WG, the work done by gravitational force: negative / positive / zero| | | | page 5Last Name First Name First three initials of last nameGrade:7. (5 points) A solid disk of mass 10.0 kg and radius 50 cm is spun from rest by two forces (F~A and F~B) shown.It is fixed at its center (x). (i) Find the net torque on the disk about its center taking the counter-clockwisedirection as positive. (ii) Find the angular acceleration of the disk. You can safely ignore the normal force andthe weight as they have no contribution to the net torque. Hint: Look at Problem 5 on midterm 2. Can you dothe same set of calculations for a solid disk?8. (5 points) A table tennis ball moving to the North is also spinning such that it deviates to the West shown in thetop view (left). If we go into the table tennis ball’s rest frame, the wind will be flowing towards the ball as shownon the right. On the figure to the right, (i) indicate the direction of the spin, (ii) draw at least three strPhysics留学生作业代做、Java，c++语言作业代写、代做Python课程设计作业 代写Python编程|帮做C/eamlineson each side of the ball, and (iii) indicate which side of the ball has a higher/lower pressure. You may eitherprint this page or just draw your response on a paper.Top View Top View (ball’s rest frame) Wind directionLast Name First Name First three initials of last nameGrade:9. Ball A traveling to the right at 5.0 m/s impacts a group of two identical balls (B and C) which are both initiallyat rest (shown on the left). After the collision, all three balls are moving, and their speeds and directions areshown on the right. All balls have the same mass of 1.0 kg. The +x and +y directions are defined for you.a. (6 points) In terms of the quantities given, write down two momentum conservation equations; one for thex-component and one for the y-component of the balls’ momenta.b. (4 points) How many independent unknowns are there in part (a)? What are they? They should be veryobvious!c. (6 points) Solve for the unknowns in part (a).d. (4 points) Is the collision elastic? Justify your answer by calculating the total kinetic energy before and afterthe collision.| | | | page 7Last Name First Name First three initials of last nameGrade:10. These questions test your general understanding of the entire course.a. (6 points) State three (and only three) distinctively different conservation laws you learned this quarter.First state the of the conservation laws in words, then present it in a form of an equation (before) = (after).Finally, write down the condition that needs to be satisfied for the quantity to be conserved.Example:xxx is conservedxxxbef ore = xxxaf terThis is true when ...b. (8 points) What are the three important elements of the Newton’s Third Law? Draw two free body diagramsof the same situation you find appropriate and demonstrate all three elements of the Newton’s Third Lawin that situation.c. (6 points) Name one energy system we learned that cannot be negative. Explain why it cannot be negative.Name one energy system we learned that can be negative. Explain why it is fine for it to be negative.| | | | page 8Last Name First Name First three initials of last nameGrade:11. A ladder of mass mL = 15.0 kg and length L = 5.0 m, which we will assume it is a uniform beam, is leaningagainst the wall on the ground. The wall is smooth and frictionless, but the ground is rough. A person(mp = 40.0 kg) is standing at rest at a distance of 3.0 m above the ground on the ladder. The entire systemis at rest. This problem is very similar to the ladder problem on page 7 of L13.pdf. Follow the prompts andyou will find all the forces acting on the ladder. Recall the static conditions are ΣF~ = 0 and Στ = 0.a. (8 points) Draw a free body diagram of the ladder+person directly on top of the above diagram.b. (4 points) Find the vertical component of the force on the ladder by the ground. State which static conditionyou are using.c. (4 points) Find the horizontal component of the force on the ladder by the ground. State which staticcondition you are using.d. (4 points) Finally, find the normal force on the ladder by the wall. State which static condition you areusing.| | | | page 9Last Name First Name First three initials of last nameGrade:12. Water from a water tank flows continuously through a pipe and eventually flows out of a horizontal cylindricalpipe of 1.0 cm in radius that is placed 2.0 m above the ground. The water level inside the water tank isassumed to be static and maintained at 30.0 m above the ground. Define point A at the water level inside thetank, point B at the beginning of the cylindrical pipe, and point C at the end of the cylindrical pipe. Assumeno energy is lost due to non-conservative force. Report all pressure as the absolute pressure.a. (5 points) Find the pressure at point B (PB). Explain. Hint: Point C is open to the atmosphere and the pipeis unifom from point B to point C.b. (5 points) Find the speed of the water at point B (vB). Hint: Find another point where you know thepressure, fluid speed, and height to use the Bernoull’s equation.c. (i) (5 points) By what percentage does one need to cover the area of the cylindrical pipe at point C suchthat the speed of water at point C is five times than that at point B? That is vC = 5vB.(ii) (5 points) Find the range of the water (R) if the pipe is covered at point C. Use only the kinematicequations. Do NOT quote any results about the range in the available resource.Useful Equations, Formulas, and ConstantsSeparate this sheet from the text packet. Do not turn it in.Kinematics in 1D:∆x = xfinal − xinitial = x − x0average speed =distance traveledtime elapsedaverage velocity = ¯v =displacementtime elapsed =∆x∆tinstantaneous velocity = v = lim∆t→0∆x∆taverage acceleration = ¯a =change in velocitytime elapsed =∆v∆tinstantaneous acceleration = a = lim∆t→0∆v∆t∆v = vfinal − vinitial = v − v0v = v0 + atx = x0 + v0t +12at2v2 = v20 + 2a(x − x0)v¯ =v + v02a = constantKinematics in 2D:~r = x xˆ + y yˆ = (x, y)~v = vx xˆ + vy yˆ = (vx, vy)~a = ax xˆ + ay yˆ = (ax, ay)~v = ~v0 + ~at~r = ~r0 + ~v0t +12~at2~v2 = ~v02 + 2~ad(d = displacement in the direction of ~a)~a = constantForces:gravity = weight = mg (downwards)|F~fr,s| ≤ µs|F~N ||F~fr,k| = µk|F~N |F~spring = −k~xCircular Motion:Energy:WF = Work = F~ · ~ri = Wtotal∆KE + ∆PE = Wnon-conservative∆KE + ∆PE = 0(When no non-conservative forces)(1-dimensional elastic collision)Angular Motion:(Direction of ~τ given by right-hand rule)L = Iω (Direction of L~ - right-hand rule)Moments of inertia:IPoint Mass = mr2IHoop = mR2ISolid Disk = ISolid Cylinder =12mR2转自：http://www.daixie0.com/contents/13/4871.html
