【AP物理C】【真题】解答题2008力学

【AP物理C】【真 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 】解答题2008力学 ?AP Physics C: Mechanics 2008 Free-Response Questions The College Board: Connecting Students to College Success The College Board is a not-for-profit membership association whose mission is to connect students to college success and opportunity. Founded in 1900, the association is composed of more than 5,000 schools, colleges, universities, and other educational organizations. Each year, the College Board serves seven million stude parennts and theirts, 23,000 high schools, and 3,500 colleges through major programs and services in college admissions, guidance, assessment, financial aid, enrollment, and teaching and ????learning. Among its best-known programs are the SAT, the PSAT/NMSQT, and the Advanced Placement Progr (APam). The College Board is committed to the principles of excellence and equit‎‎tmenty, and that commi is embodied in all of its programs, services, activities, and concerns. ? 2008 The College Board. All rights reserved. College Board, Advanced Placement Program, AP, AP Central, SAT, and the acorn logo are registered trademarks of the College Board. PSAT/NMSQT is a registered trademark of the College Board and National Merit Scholarship Corporation. Permission to use copyrighted College Board materials may be requested online at: www.collegeboard.com/inquiry/cbpermit.html. Visit the College Board on the Web: www.collegeboard.com. AP Central is the official online home for the AP Program: apcentral.collegeboard.com. ? 2008 The College Board. All rights reserved. Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for students and parents). PHYSICS C: MECHANICS SECTION II Time-45 minutes 3 Questions Directions: Answer all three questions. The suggested time is about 15 minutes for answering each of the questions, which are worth 15 points each. The parts within a question may not have equal weight. Show all your work in the pink booklet in the spaces provided after each part, NOT in this green insert. 2008M1. A skier of mass M is skiing down a frictionless hill that makes an angle , with the horizontal, as shown in the diagram. The skier starts from rest at time t = 0 and is subject to a velocity-dependent drag force due to air resistance of the form F = –bv, where v is the velocity of the skier and b is a positive constant. Express all algebraic answers in termsM, b, of ,, and fundamental constants. (a) On the dot below that represents the skier, draw a free-body diagram indicating and labeling all of the forces that act on the skier while the skier descends the hill. (b) Write a differential equation that can be used to solve for the velocity of the skier as a function of time. (c) Determine an expression for the terminal velocity of the skierv. T (d) Solve the differential equation in part (b) to determine the velocity of the skier as a function of time, showing all your steps . (e) On the axes below, sketch a graph of the acceleration a of the skier as a function of time t, and indicate the initial value of a. Take downhill as positive. a O t ? 2008 The College Board. All rights reserved. Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for students and parents). 2008M2. The horizontal uniform rod shown above has length 0.60 m and mass 2.0 kg. The left end of the rod is attached to a vertical support by a frictionless hinge that allows the rod to swing up or down. The right end of the rod is supported by a cord that makes an angle of 30? with the rod. A spring scale of negligible mass measures the tension in the cord. A 0.50 kg block is also attached to the right end of the rod. (a) On the diagram below, draw and label vectors to represent all the forces acting on the rod. Show each force vector originating at its point of application. (b) Calculate the reading on the spring scale. 12ML(c) The rotational inertia of a rod about its center is , where M is the mass of the rod and L is its length. 12 Calculate the rotational inertia of the rod-block system about the hinge. (d) If the cord that supports the rod is cut near the end of the rod, calculate the initial angular acceleration of the rod-block system about the hinge. 2008M3. In an experiment to determine the spring constant of an elastic cord of length 0.60 m, a student hangs the cord from a rod as represented above and then attaches a variety of weights to the cord. For each weight, the student allows the weight to hang in equilibrium and then measures the entire length of the cord. The data are recorded in the table below: Weight (N) 0 10 15 20 25 Length (m) 0.60 0.97 1.24 1.37 1.64 (a) Use the data to plot a graph of weight versus length on the axes below. Sketch a best-fit straight line through the data. ? 2008 The College Board. All rights reserved. Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for students and parents). (b) Use the best-fit line you sketched in part (a) to determine an experimental value for the sprink of g constant the cord. The student now attaches an object of unknown mass m to the cord and holds the object adjacent to the point at which the top of the cord is tied to the rod, as represented above. When the object is released from rest, it falls 1.5 m before stopping and turning around. Assume that air resistance is negligible. (c) Calculate the value of the unknown mass m of the object. (d) i. Calculate how far down the object has fallen at the moment it attains its maximum speed. ii. Explain why this is the point at which the object has its maximum speed. iii. Calculate the maximum speed of the object. ? 2008 The College Board. All rights reserved. Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for students and parents).