Physics 171/171H Introductory
Physics: Mechanics and Relativity
M T Th F 9:00 AM, Room 1402 Physics (171H will meet separately on Thursdays with Prof. Goldenbaum) Instructor: Professor E. Williams Study Sessions: 2:305:30 Thursday, Conference Room  2120 PhysicsOffice: Room 2332 Physics These are informal group study sessions, where the professor or TA will be available to answer questions individually. You should feel free to stop by briefly at any time during the study session to ask a few questions, or to stay there to study or participate in discussions of other students' questions as well as your own. Course Textbook: Physics, 4th Edition, Volume I, Resnick, Halliday and Krane (not all material in each chapter will be covered) Six Ideas that Shaped Physics: Unit N and Unit C, T. A. Moore 2. Attendance and quizzes 3. In Class Exams: Exam 1: Tues., Oct. 3 4. Final Exam: Friday, December 15, 1:30 PM InClass Exams 50% (40% for 171H) Final Exam 25% Room 4210 Physics Miscellaneous Course Information Homework assignments will be posted on the course web site. If you didn't get the assignment when announced in class, or if you lost it, you can find it on the site. Homework, Quiz and Exam solutions will be posted on the course web site only. Quizzes will be given usually once a week. The quiz problems will be examples worked in class during the previous lecture, or sample problems from the assigned reading in the text unless otherwise announced. Assistance outside of the course is available from several sources: Provides general academic support for physics majors and students enrolled in physics courses Bernie Kozlowski: 3014055949 2201 Shoemaker Building, 3013147693 1117 Hornbake Library (Division of Letters and Sciences) 1101 Hornbake Library Building
Quizzes and Exams Homework 1) Use some common sense. Any given homework problem is about 1/10 of 1/13 of 1/5 of your grade. Think about that before spending a lot of time disputing over partial credit. 2) Don't ask for consideration of changed credit without first looking at the posted solution sets and making sure you really DID do the problem properly. 3) IF after considering points 1 & 2, you still have a question,
then you can write a note explaining the question, attach it, and a
copy of the relevant page from the solution set, to your HW set and
give it to Dr. Williams, who will forward it to the TA for consideration.
You should circle on your solution set, in a different color ink, the
answer that you are worried about. Changes in working exam: Repeat problems 1, 3 and 4 as on the original exam. The corrected figure for problem 3 is: (As far as I can tell, everyone who did the problem assumed that this was what I meant.) Problem 2: Instead of parts a, b and c, do the following: Calculate the height mass m2 rises before its speed reaches zero, using:
Remember: If some of the forces doing work are conservative forces where we know the dependence of force on distance, we can calculate a potential energy change and relate its negative to the work done by that force. Then we have: This approach is needed for problem 2 and problem 3c. Remember: The relationship between period and radius of an orbit was derived FROM the gravitational force law. If we didn't know the gravitational force law, the periodradius relationship would also be unknown.
Reading and Problem Assignments Suggested study plan: Begin by reading over the assigned
problems for each chapter. Then look through the figures, tables
and sample problems in the chapter. This will give you an idea of
the material is organized and help you focus as you read the chapter.
Then read through the chapter, keeping in mind the questions that have
been assigned for homework. Work through the example problems carefully.
At the end of each section, see if you can do the assigned problems that
correspond to that section. Mark down questions if you get stuck
and ask questions in class. Don't wait until the night before the
homework is due to begin working the problems!! (You'll also get
a lot more out of the study sessions if you've looked at the problems
before you walk in the door.)
S.21. A sample of hydrogen gas (hydrogen = H2, molecular weight
= 2.0 grams/mole, distance between H atoms in the molecule is 0.074 nm)
is at 500K. At this temperature, rotations of the molecule are allowed
but vibrations are not. S.22 A cubical box with lengthofside L contains N particles of
which S23. A diatomic ideal gas is held in a box of volume 9 m^{3},
at a temperature a) How much gas is in the box? b) The gas is heated to 600K without changing
volume. How much heat c) Then the gas is slowly allowed to expand
at constant temperature d) Draw a pressurevolume diagram for
the two step expansion of the gas S24. A monoatomic ideal gas is confined in a twodimensional container
a) What is its internal energy? (Hint:
how many translational degrees of b) If the atomic mass of the atoms in
the gas is 28.1 g/mole, what is the c) The distribution of speeds of the atoms
is found to obey the equation:
Extra Credit Problems (up to 5 points each on homework score) S.16 Two skaters, each of mass 50.0 kg, approach each other along parallel pathes separated by 3.0 m. One skater has velocity 10 m/s and the other has velocity 10 m/s both in the x direction. The first skater carries a massless pole of length L = 3.0 m. The second skater grabs the end of it as he passes by. Assume frictionless ice and treat the skaters as point particles. a) What is the velocity of the system center of mass (system = 2 skaters + pole)? b) What are the translational and angular velocities of each of the skaters after they are connected by the pole? c) By pulling on the pole the skaters reduce their separation to 1.0 m. What are their translational and angular velocities then? d) Compare the kinetic energies of the skaters before the collision, after the collision, and after they have reduced their separation. Where do the changes come from? e) What quantities are conserved in parts bd? S.17 Do problem 21 in Chapter 13 of the book. S.18 Consider the same configuration as for problem S.17 (a point
particle hitting a thin rod normal to its length), but now the collision
is inelastic. Compare the change in kinetic energy during the collision
for d = 0 and for d = L/2. Use the values L = 2.2 m, m1 (the
point particle ) = 2.0 kg, m2 (the rod) = 2.5 kg, and vo (the initial
speed of the point particle) = 1 m/s.
Problem Set: Due at the beginning of class, MONDAY, Nov. 20 Ch. 12, # 6, 8, 20, 24, 44, 50 Ch. 13, #2, 12, 28, 34, 36 Problem S13 Extra Credit (up to 20% extra on this hw score) S14, S15 If you are having trouble with concepts or problem solving in chapter 10, you might find it helpful to see a different approach in the supplemental material: Circular motion, rotational motion, angular momentum: Reif Chs.
8, 17, 18 S13 A particle of mass m is attached to a string which passes
through a hole in a table. The particle rotates without friction
on the table around the hole with speed v and radius R. S14 A small mass, m, is moving in the vicinity of a large
mass M. The large mass is so much larger that it undergoes no observable
acceleration due to its gravitational interaction with the small mass.
(Bold symbols, for instance r_{2}, indicate vectors.
Nonbold symbols, for instance r_{2}, indicate the magnitude of
the vector.) The zero of the coordinate system is the center of
the large mass. S15 A large solid sphere of mass m2 = 5.0 kg and radius R = 0.50
m is suspended from a pivot by a rigid massless rod. The distance
of the center of mass of the sphere from the pivot is L =
1.2 m. A point particle of mass m1 =2.5 kg and a horizontal initial
velocity of v0 = 6.0 m/s hits the large sphere headon and sticks to it.
If you are having trouble with concepts or problem solving in chapter 10, you might find it helpful to see a different approach in the supplemental material: Collisions: Reif Ch. 16, Section C Problem Set: Due at beginning of Class, Nov. 10 S10. A stationary nucleus of mass 107mp, where mp is the rest mass of
a proton, breaks apart (decays) into two particles. One of the particles
has rest mass m1 = 20mp and speed v1 = 0.89c. S11. If a relativistic collision occurs elastically, that is with no change in the total kinetic energy of the particles involved, what is the change in the total mass of the particles involved? EXTRA CREDIT:
Problem Set, Due at beginning of Class, Nov. 3 Chapter 9 # 10, 16, 18, 24, 36, 38 If you are having trouble with concepts or problem solving in chapter 9, you might find it helpful to see a different approach in the supplemental material: Momentum and Center of Mass: Reif Ch. 15
Problem Set, Due at beginning of Class, Oct. 27 Chapter 8 # 8, 14, 20, 30, 52, 66 Chapter 16 # 30, 36, 40 Chapter 21 # 50, 52 If you are having trouble with concepts or problem solving in chapter 8, you might find it helpful to see a different approach in the supplemental material: Potential Energy: Reif Ch. 14 Problem Set, Due at beginning of Class, Oct. 20 Chapter 7 # 8, 10, 14, 26, 38, 50, 62 Chapter 16, # 44, 46 Supplemental Problem S9 If you are having trouble with concepts or problem solving in chapter 7, you might find it helpful to see a different approach in the supplemental material:
An object of mass 0.6 kg is sliding around the inside of a cylinder of radius 1.8 m. One half of the cylinder’s inner surface is frictionless, and the other half is rough with kinetic coefficient of friction m_{k} = 0.2. The mass initially is moving on the smooth surface with constant speed of 2 m/s. a) Draw a force diagram for the object after it has entered the rough part of the cylinder. What is the magnitude of the frictional force just after the object has entered the rough part? Problem Set, Due at beginning of Class, Oct. 13 Chapter 6, # 10, 16, 24, 28, 34, 36, 40, 50 Chapter 16, # 6, 12 If you are having trouble with concepts or problem solving in chapter 6, you might find it helpful to see a different approach in the supplemental material: Springs, Friction, Orbits: Reif Ch. 8, 12
Problem Set, Due at beginning of Class, Oct. 6 Chapter 5, # 4, 10, 18, 36, 38, 46, 50, 56 If you are having trouble with concepts or problem solving in chapter 5, you might find it helpful to see a different approach in the supplemental material: Newtonian Mechanics: Reif Ch. 911
Problem Set, Due at beginning of Class, Sept. 29 Chapter 21 # 2, 4, 14, 16, 20, 22 Supplemental Problems S5, S6, S7, S8
S5. Among the particles of highenergy physics are charged pions. They can be produced by bombarding a target in an accelerator with highenergy protons. The pions leave the target with speed close to that of light. The pions are radioactive, and when they are brought to rest, their halflife is measured to be 1.8x10^{8} s. That is half of the number present at any time have decayed 1.8 x 10^{8}s later. In a collimated pion beam, of speed 0.99c, 50.0% of the pions have decayed by the time the beam has traveled to 38m from the target. Problem Set, Due at beginning of Class, Sept. 22 Chapter 4 # 52, 56, 72, 76, 78 Chapter 21 # 2, 4, Supplemental Problems S1, S2, S3, S4 (below, or download .pdf file ) If you are having trouble with concepts or problem solving , you might find it helpful to see a different approach in the supplemental material: Circular motion and relative motion: Reif, Ch. 8; Moore Unit N,
Ch. 9 and 10 S1. Vector description of circular motion. Plot the x position of the particle vs. timeS2. A firecracker explodes 30 km away from an observer, who is sitting next to a clock A. The light from the firecracker explosion reaches the observer at exactly t = 0, according to clock A. Imagine that the flash of the explosion illuminates the face of another clock B which is sitting next to the firecracker. What time would clock B register at the moment of illumination, if it is correctly synchronized with clock A? Express your answer in milliseconds. S3. Imagine that you are in an inertial frame in empty space with a clock, a telescope and a powerful strobe light. A friend is sitting in the same frame a very large (unknown) distance from your clock. At precisely 12:00:00 noon, according to your clock, you set off the strobe lamp. Precisely 30.0 seconds later, you see in your telescope the flash of your friend’s clock illuminated by your strobe flash. How far away is your friend? What should you see on the face of your friend’s clock if that clock is synchronized with yours? S4. Physical understanding of trajectories:
Problem Set, Due at beginning of Class, Sept. 15 Chapter 3 # 8, 10, 16, 20, 24, 38, 48 Chapter 4 # 8, 14, 24, 40, 44 If you are having trouble with concepts or problem solving in chapters 3 and 4, you might find it helpful to see a different approach in the supplemental material: Trig, vectors: Moore (Six Ideas, Unit C), p. 38, 54, 17980
Problem Set 1, Due at beginning of Class, Sept. 8 Chapter 1 # 18, 30, 40 Chapter 2 # 14, 18, 22, 30, 40, 48, 60, 66 If you are having trouble with concepts or problem solving in chapters 1 and 2, you might find it helpful to see a different approach in the supplemental material: Graphical analysis of 1dimensional Motion: Moore, Unit N, p.
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Physics 171/171H  Spring 2000

Physics 171/171H  Spring 2000
