PHYSICS 207 - ANNOUNCEMENTS

Physics 207 General Physics I

University of Wisconsin-Madison Fall 2006

ANNOUNCEMENTS: Last updated on 11/27/06

All course announcements/changes will be posted here.
If a really major announcement occurs then a separate e-mailing of this will be made to all enrolled students.

08/26/06: If you wish to get a head start some of the assignments are already posted. Note that we will use the on-line homework engine provided for Serway and Jewett at www.webassign.com
(Last revised 09/01/06)

To begin you should click on the "log in" icon. If you have a UW e-mail address then you should already have an account. Your UW username is your Webassign name (no @wisc.edu). The institution is wisc. Your password, if everything has been done right, should be the last four digits of your student ID number. If that doesn't appear to work you can have the password sent to your e-mail address.

The first homework assignment will be available on 9/5/06 or 9/6/06.

There is a required assignment that runs you through some of the WebAssign features.

This is the first time that I have used WebAssign and so everyone is on the learning curve (i.e. have patience please).

09/01/06: There will be no laboratories the first week of class. If you have a discussion section on Tuesday the meeting with your TA will likely be rather brief. The class will start in earnest after Wednesday's lecture.

09/06/06: Link to Lecture 1; PowerPoint , Lecture 1; pdf

09/11/06: Link to lecture, Lecture 2, PowerPoint , Lecture 2(pdf)

A few of the consultation room times have been shifted. By Friday it should be pretty much specified.

09/13/06: Link to lecture, Lecture 3, PowerPoint , Lecture 3(pdf)

09/18/06: Link to lecture, Lecture 4, PowerPoint , Lecture 4(pdf)

Chapter 3-4 homework should be accessible now. Note: There have been a few slight modifications from the original syllabus. Serway: Ch. 3: 8, 32, 36, 38, 54 and Ch. 4: 4, 6, 18, 34, 45, 55 using the WebAssign provided problems.

09/20/06: Link to lecture, Lecture 5, PowerPoint , Lecture 5 (pdf)

Comment: Lecture 5 will have to slide into Monday and that will push hard on the homework deadline. I will move it forward to Wednesday, Sept. 27 at noon.

09/25/06: Link to lecture, Lecture 6, PowerPoint , Lecture 6 (pdf)

Homework 3 should be available now. There are some slight changes from the original syllabus.

All students that are unable attend the first mid-term time slot should have communicated that information by now.

Lecture 6 ended at kinetic friction. Static friction will be covered on Wednesday

09/27/06: Link to lecture, Lecture 7, PowerPoint , Lecture 7 (pdf)

Homeworks 3 (and from now on) due date will shift to 11:59 PM on Tuesday

Lecture 7 ended with uniform circular motion with friction.

Monday is a catch up day and we will look at non-uniform circular motion, frames of reference and talk just a wee bit about resistive forces (i.e., drag).

By Monday I will provide a link to a number of illustrative cooperative learning questions. You may or may not have had them in discussion. I will also create a non-graded exercise set on Web-Assign for those wishing to run through a few more problem.

There is a link to sample exams on the course information page. The 2004 exam is typical of the level with the proviso that it was a 60 minute exam.

10/02/06: Link to lecture, Lecture 8, PowerPoint , Lecture 8 (pdf)

Cooperative learning questions are now posted at the library and can be accessed through my.wisc.edu

Accelerated frames of reference: Observing in an accelerated frame of reference creates the need to provide fictitious forces. The box/train problem is more accessible if one uses an inertial reference frame (a = 0). From this perspective the force of friction on the box is towards the front of the train car (as it should be) but the train car experiences a larger acceleration.

Because of the supplemental 3a homework set students, I will allow for substitutions by either 5.26 or 6.36 using the WebAssign values. The handing of work is to make sure you are keeping up.

10/04/06: Link to lecture, Lecture 9, PowerPoint , Lecture 9 (pdf)

Midterm I in Rm. 105 and 113 in Psychology, McBurney students go to Rm. 5310 Chamberlin Hall (on Thursday Oct. 5)

Exam lasts from 7:15 PM to 8:45 PM. Bring a basic scientific calculator (up to a TI-84), an 8.5 x 11 in sheet of notes. We can provide blank paper for scratch work but only work on the exam sheets itself will be graded.

Slide with friction notes

10/09/06: Link to lecture, Lecture 10, PowerPoint , Lecture 10 (pdf)

Midterm 1 has been graded and will be returned during the next discussion section. Exam statistics and a conservative grade assessment are part of the lecture notes. The test key can be accessed through my.wisc.edu

Regrades: Because partial credit is given the assigned scores reflect a subject assessment of work done. If you feel that the grader made an error (it does happen) or the partial credit is inconsistent with your expectation then please return your exam with a short note stating your request and why. All regrades will be discussed during the TA meeting on Friday.

10/11/06: Link to lecture, Lecture 11, PowerPoint , Lecture 11 (pdf)

Almost everyone gave the correct answer to the ball drop path exercise. That is great(!) because historically this concept problem often gives students difficulty.

Regrades: There is a deadline of Monday, Oct. 16 for requesting a regrade.

10/16/06: Link to lecture, Lecture 12, PowerPoint , Lecture 12 (pdf), Up to exercise 4

We will finish impulse and center of mass on Wednesday
Regrades: Today is the deadline for requesting a regrade.
A revised tutor list is now available, please stop by my office to get one
Alternative problems to hand in : Ch 7-32 or Ch 8-10.
HW #5, Ch. 9: 4, 19a,b, 31, 41, 64, Ch. 10, 7, 19a,b, 20, 31, 33, 71 (and one more is likely)
Momentum is yet another way of casting Newton's Laws in which a collision occurs. Momentum is a vector quantity and so we must consider the vector component individually.

10/18/06: Link to lecture, Lecture 13, PowerPoint , Lecture 13(pdf), Up through moment of inertia

Center of mass and rotational inertia are just specialized perspectives for dealing with Newton's Law of motion. In the case of center of mass the issue is that no matter how complicated a system is the center of mass reflects the momentum transfer to an object as a result of an external force. If no external force then the velocity of the center of mass remains a constant of the motion.
In the case of rotational motion around an explicit axis the rotational inertial plays the same role as the mass in linear motion. Objects with large rotational moments of inertia are more difficult to spin (i.e., accelerate angularly) than those with small moments of inertia. There are important differences. The center mass may be specified by the mass distribution but the resistance (i.e., inertia) to linear acceleration doesn't depend on this distribution. For rotational motion we must specify the axis of rotation and mass which is father away from the axis exhibits a stronger inertia to being spun that mass that is closer to the axis of rotation.

10/23/06: Link to lecture, Lecture 14, PowerPoint , Lecture 14 (pdf) , Up to cross products

The homework will not dwell on the motion of a top nor quantization of angular momentum in quantum systems. Still I encourage you to read through Chapter 11.

Chapters 11 and 12 are rather modest in length.

The second midterm will be on Thursday evening of next week.

HW #6 is available on WebAssign. There are some changes from the syllabus: Ch 10-79, Ch 11-17,23,30,35,44abdef Ch 12-4,9,21,32,35

10/25/06: Link to lecture, Lecture 15, PowerPoint , Lecture 15 (pdf)

The second midterm will be at 7:15 PM, Thursday of next week, Room, TBA
Key points: If there is no net external force on system then linear momentum is conserved. If there is no net external torque then angular is conserved. Question: Can you imagine a case where linear momentum is conserved and angular momentum is not?

10/30/06: Link to lecture, Lecture 16, PowerPoint , Lecture 16 (pdf)

Midterm I in Rm. 105 and 113 in Psychology, McBurney students go to Rm. 5310 Chamberlin Hall (on Thursday, Nov. 2)

Exam lasts from 7:15 PM to 8:45 PM. Bring a basic scientific calculator and an 8.5 x 11 in sheet of notes. We can provide blank paper for scratch work but only work on the exam sheets itself will be graded.

Most students are really most interested in getting ready for the midterm. To this end a supplemental set (Ch. 11 and Ch. 12) with four problems is available. Because time is short (!) I want to minimize the long hours and so the "exchange" is one for one. The deadline on the supplemental set is noon on Wednesday. In addition only parts a and b are required for the loop-the-loop problem and parts a,b and d for the draw bridge problem. Hint: At the angle given the draw bridge should fall faster that the horse. Check the linear acceleration of the point under the horse.

An important point is that friction is a tangential force and will always provide a torque. This is true of both static and kinetic friction.

11/01/06: Link to the lecture, Lecture 17, PowerPoint , Lecture 17 (pdf)

Midterm I in Rm. 105 and 113 in Psychology, McBurney students go to Rm. 5310 Chamberlin Hall (on Thursday, Nov. 2)
The exam lasts from 7:15 PM to 8:45 PM. Bring a basic scientific calculator and an 8.5 x 11 in sheet of notes. We can provide blank paper for scratch work but only work on the exam sheets itself will be graded.
Reminder: November 3rd is the last day for dropping a class, if you have major concerns then contact your TA first and then me. On a very limited number of cases we can give an estimate of your mid-term grade before 3 PM.
Main points: If no net external force, momentum is conserved. If no net external torque, angular momentum is conserved. This is true piecewise in the x, y and z directions. The equations look simple but the physics is not. Thus if there is a net external force then a system will accelerate. If there is a net external torque then a system will have angular accelerations. A single force can be the source of acceleration and angular acceleration.
Integrals: It turns out there is one small "integral" on the exam. If you know the equation for the area of a triangle then this integral can be done without having to mechanically go through the process of integration. (It is similar to a few of the prior homework problems.)

11/06/06: Link to the lecture, Lecture 18, PowerPoint , Lecture 18 (pdf)

MidTerm 2 is graded: Mean 58.4, Median 58, St. Dev. 16
Given the level of difficulty the class did much better than I was expecting. The material was much harder and the exam itself was more difficult than the first mid-term. You are expected to cover a lot of material and, given the good results of the first exam, I became too ambitious and raised the bar a bit too high. Even though the the average dropped a somewhat I am pleased to see so many students working so hard. Rotational motion is a very difficult subject.
The tentative (conservative) curve is on the first page of the lecture note. My thought is that ~30 and above
represents a clear passing grade. Low exam scores (ca. 25-30) can be mitigated to a large extent with evidence of good discussion/lab/homework performance. If you continue to work through the material, you can expect to pass. Perhaps it may be possible to improve as there are still two exams to go and the rest of the course is somewhat less difficult.
The key to solving buoyancy problems is to alway reference the volume of the fluid displaced. Using that as fixed point will get you the bouyant force or the work done in a force amplifier.
HW#7 Ch. 14: 2,8,20,30,52a,54 Ch. 11,19,36,41,49 Honors: Ch. 14: 58
Regrades: The deadline for requesting regrades is Tuesday, Nov. 14.
Link to lecture notes: Physics of Utrasound honors lecture

11/08/06: Link to the lecture, Lecture 19, PowerPoint , Lecture 19 (pdf)

Regrades: There were, in retrospect, a few additional anomalies in the exam questions and these need to be addressed. Please hand in your exam to your TA as soon as possible. The deadline for requesting regrades is Tuesday, Nov. 14.

Oscillatory Motion, especially simple harmonic motion, is a common phenomenon for systems with a linear restoring force (i.e., Hooke's Law).

11/13/06: Link to the lecture, Lecture 20, PowerPoint , Lecture 20 (pdf)

Regrades: The deadline for requesting regrades is now Thursday, Nov. 16.

Mid-term 3, yes it isn't too soon to start thinking about the third midterm exam. To keep in sync with the course material I have decided to give the exam on Tuesday evening, November 28. Please contact me before the Thanksgiving holiday if you can't attend. The exam covers material from chapters 14 through 18. Thereafter there is just four more chapters to go.

Homework #8, There have been a few changes, Ch. 16: 3, 18, 30, 40, 58, 59 Ch. 17: 3,15, 34, 38, 40

Note that the next homework (#9) set includes just one chapter.

11/15/06: Link to the lecture, Lecture 21, PowerPoint , Lecture 21 (pdf)

Regrades: The deadline for requesting regrades is tomorrow Thursday, Nov. 16.

Mid-term 3,To keep in sync with the course material the third exam on Tuesday evening, November 28. Please contact me before the Thanksgiving holiday if you can't attend. The exam mostly covers material from chapters 14 through 18.

Note: The traveling wave equation is an extension of simple harmonic motion. The basic expression is (of course) y(x,t) = A cos(k x - omega t + phi). In class I let phi be zero for simplicity. On the first homework problem you won't be able to do this. This is a wave that varies in space and time with the velocity of energy flow given by v = lambda/ T = omega / k . Notice that there are two velocities that must be reconciled, that of the energy flow and that of the mass element situated at a point on the string. Thus you must consider independently two facets of the wave; either at fixed position or at fixed time. Now x, y and t must reconciled and hence wave motion is more difficult than SHM (simple harmonic motion).

At fixed t: Let t=0 and so now we have y(x,0) = A cos(kx + phi) and this will give the displacement of the string every in space.

At fixed x: Let x=0 and so now we have y(0,t) = A cos(-omega t +phi) and this will give the displacement of a specific piece of the string with time. We can get its position y if we know t, omega, A and phi or its velocity from dy/dt = omega A sin(-omega t +phi) if we know t omega, A and phi. This the "second" velocity and describes the local motion of the disturbance. For the first homework problem you will need to use this fact.

NOTE: Problem 2 on the homework. This problem actually references a sine wave (although everything is set up in the text for a cosine). So now you need to start with y(x,t) = A sin(-kx - omega t +phi ) or A sin(kx+ omega t + phi). Of these WebAssign wants you to choose the later. These multivalued solutions can be problematic.

11/20/06: Link to the lecture, Lecture 22, PowerPoint , Lecture 22 (pdf)

Mid-term 3,To keep in sync with the course material the third exam will be on Tuesday evening, November 28. Please contact me before the Thanksgiving holiday if you can't attend. The exam mostly covers material from chapters 14 through 17 (plus elasticity and moduli).

This mid-term builds on concepts developed in the first twelve chapters and so you should remember to copy important formulas from the first two exams on your note sheet. If you happen to forget to include one then you are, by all means, welcome to ask the TA proctoring the exam for assistance.

Note 1: Even though I will lecture on Chapter 18 on Wednesday, this material will only appear on the final. Homework set #9 will be lumped together with that of Chapter 19 and due two weeks from tomorrow.

Note 2: Monday, Nov. 22 will be a review section for the exam

Note 3: Homework #8 will be due on Wednesday at noon.

11/22/06: Link to the lecture, Lecture 23, PowerPoint , Lecture 23 (pdf)

The third exam will be on Tuesday evening, November 28 (again in the Pyschology lecture halls). The exam mostly covers material from chapters 14 through 17 (plus elasticity and moduli). McBurney students should go to room 5310 in Chamberlin Hall.

This mid-term builds on concepts developed in the first twelve chapters and so you should remember to copy important formulas from the first two exams on your note sheet. If you happen to forget to include one then you are, by all means, welcome to ask the TA proctoring the exam for assistance.

Monday, Nov. 27 will be a review section for the exam

Have a good Thanksgiving holiday

11/27/06: Link to the lecture, Lecture 24, PowerPoint , Lecture 24 (pdf)

The third exam will be on Tuesday evening at 7:15 PM on November 28 (again in the Pyschology lecture halls). The exam mostly covers material from chapters 14 through 17 (plus elasticity and moduli). McBurney students should go to room 5310 in Chamberlin Hall.

In the class I noted that there are parallels between the natural resonant angular frequency in torsional motion for a physical pendulum or a torsional pendulum whether the force is due is to gravity or a Hooke's Law spring. In all cases omega^2 is proportional to something torque-like in the numerator and rotational inertia like in the denominator. Of course the actual numerical values are example specific.

11/29/06: Link to the lecture, Lecture 25, PowerPoint , Lecture 25 (pdf)

Temperature is ubiquitous in our daily lives but its actual physical meaning is difficult to discern. For example if you touch a 0 C piece of metal or a 0 C piece of cloth you might be inclined to say that the metal feels colder even though they are really at the same temperature. Here you are prejudiced by the heat flow. In thermodynamics temperature is the property of a system which tells you the net direction that heat will flow if two objects are brought into thermal contact (i.e., heat transfer is possible). Heat flows from high temperature objects towards low temperature objects. At thermal equilibrium between two objects there will be no net heat flow and the objects will be said to be at the same temperature.

This said we now note that temperature can be related to the internal energy of a system. Generally as materials cool from high temperature to low temperature the internal motions of the constituents decrease. After one defines temperature reference standards, i.e. the boiling point of water at a specific pressure and the triple point of water, then one can deduce a temperature at which all classical internal energy will go to zero. The point is called absolute zero. At absolute zero all motion does not cease because of the nature of quantum mechanics. At low temperatures many materials show new striking behavior resulting from quantum properties (i.e., superconductivity).

NOTE: Because of a committee assignment I will not be able to hold my usual office hours on Monday. Please contact me by e-mail and I will do my best to meet with you after 5 PM on Monday or Tuesday.

12/04/06: Link to the lecture, Lecture 26, PowerPoint , Lecture 26 (pdf)

NOTE: Because of a committee assignment I will not be able to hold my usual office hours on Monday. Please contact me by e-mail and I will do my best to meet with you after 5 PM on Monday or Tuesday.

12/06/06: Link to the lecture, Lecture 27, PowerPoint , Lecture 27 (pdf)

Although I have stressed the importance of temperature as an indicator for determining heat flow (a process) there are addition relationships between the internal energy of a system and temperature. Here we are told that classically, for each "degree of freedom", there is a factor of 1/2 k_B T in internal energy per particle. For a monoatomic classical gas the x, y and z motions can be individually added R(vector) = x i(unit vector) + y j(unit vector) + z k(unit vector) with a resulting energy of 1/2 m (v_x^2+v_y^2+v_z^2) (i.e., three independently added terms) so that the total internal energy per particle is 3/2 k_B T.

Student evaluations will be administered on Dec. 13.

NOTE: There is a room change for the final. The location will be announced next week.

12/11/06: Link to the lecture, Lecture 28, PowerPoint , Lecture 28 (pdf)

NOTE: Room assignment for final, the Physics 207 Final exam is on Dec. 19 at 2:45 pm in Rooms B130 Van Vleck and B102 Van Vleck. McBurney student tentative room assignment: 5310 Chamberlin Hall. If all goes well we should have grades available by Thursday evening.

NOTE 2: Before lab this week you will be given the same exercise set that you received during the first day of discussion. Our goal is to establish a series of metrics to assess learning and improve the delivery of our introductory classes. We really appreciate your assistance in this process.

Today we just started talking about the efficiency of thermodynamic cycles and the 2nd Law of Thermodynamics. On Wednesday we will finish.

Student evaluations will be administered on Dec. 13.

On Friday there will be a review session for the final.

Homework 10, 2nd problem (the lead bullets): There seems to be a snafu with the WebAssign answer key. Please wait until I hear from the WebAssign people that the problem has been fixed. My apologies if this caused frustration.

Homework 11 is now accessible. Chapter 22 problems: 6,7,17,37,46

12/11/06: Link to the lecture, Lecture 29, PowerPoint , Lecture 29 (pdf)

NOTE: Room assignment for final, the Physics 207 Final exam is on Dec. 19 at 2:45 pm in Rooms B130 Van Vleck and B102 Van Vleck. McBurney student room assignment: 5310 Chamberlin Hall. If all goes well we should have grades available by Thursday evening.

Today I talked about reversible and irrevsible processes. In a reversible adiabatic expansion (Q=0) we would expect the change in entropy to be zero. There is a two term formula given in class (derived in Serway and in the lecture notes) that reflects the change in entropy for the volume change (up) and the temperature change (down). As "anticipated" the sum of these two terms is indeed zero. This is explicitly done in the lecture notes (but, as far as I can tell, not in Serway). Therefore, in the Carnot cycle, any net change in the entropy occurs during the two isothermal steps. These must be equal in magnitude and opposite in sign because entropy is a state variable. Thus in a full cycle, S_initial = S_final, and so any net change in entropy of the system (here engine plus reservoirs) reflects the heat transfer between the reserviors. In the perfect Carnot cycle there will be a drop in the entropy of the high temperature reservoir and an increase in that of the low temperature reservoir. With the perfectly reversible Carnot cycle these too are equal and opposite. Example: 200 K and 100 K with 100 J of heat transfer out of the 200 K reservoir. Efficiency is 0.50 so 50 J of work and 50 J of heat transfer goes into the 100 K reservoir. Delta_S= -100 J/200 K + 50 J/100 K =0. The Carnot cycle is the best you can do without violating either the first or second laws of thermdynamics!

Friday's class will be a review session for the final

Chapter 22 problems: 6,7,17,37,46. Due Friday at midnight.

Biocore students, please contact me if you are concerned about back to back exams.

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