Wednesday, May 7, 2014

Final grades

I've just posted your final grades on myBama, and I just updated the gradebook on Blackboard to include your final exam scores and overall averages. Have a look.

The final exam average was about 80%. For the problems portion you averaged 78.9%, and for the multiple choice you averaged 79.5% after scaling. The problems section went well, and there was no scaling. The multiple choice section went ... less well. The raw average was in the 60% range, so I scaled it by taking your best 9 out of 12 multiple choice questions and adding 7% (with a maximum of 107% on this section). The average of the multiple choice and problems sections then determined your final exam grade, and the class average was about 79.2% for the final exam as a whole, with a standard deviation of 13%.

Quite a few people changed grades (like B+ to A- and vice versa) as a result of the final. Many went up, many went down. On average, your final exam grades were about 2% lower than your average going into the final. Not many of you changed by more than half a letter grade, but some of you did. Those are the breaks, and I really hate doing it. Assigning final grades is agonizing, even when it is basically just by-the-numbers, and even after all the scores are in and the grades calculated it takes me hours to pull the trigger and submit grades.

In the end, the overall class average was 85.5% with a standard deviation of 8.65%, which is quite high. Most of you got A's and B's, and I'm fine with that.

I know some of you will be oddly surprised by a higher-than-expected grade, but a good number of you will also be annoyed by a lower-than-expected grade. Look at your final exam scores and overall grade breakdown on BlackBoard, and keep in mind that the final exam was worth quite a bit (so it was possible to change your grade by a fair amount).

If things don't seem to add up, or you have questions, let me know ASAP - we have just under 24 hours to easily alter things before the deadline if a mistake is found. 

Tuesday, May 6, 2014

Final grades are not ready yet

Those aren't the final grades on Blackboard - I'm still not finished grading the final exams. I should have the finals graded by the end of the day, and hopefully I'll have final grades calculated this evening.

I'll post here when the grades have been updated so you know for sure, and I will also include a column for the final exam score on Blackboard.

Thursday, May 1, 2014

IMPORTANT NOTICE

At 5am Friday morning, the power is going out in the building that has the server hosting all of my of my PH125 files. While this page will remain up (being hosted by Google), all old and current HW, exams, etc will not be available from 5-6am or so.

(The relevant server was actually turned off preventatively late this afternoon, as I had forgotten to tell the IT guy I really needed it to stay up. He agreed to keep it running up until the power outage, though I may owe him a beer now.)

This should not be a problem, but just in case you find dead links, I'm copying all of my old PH101, PH105, and PH125 material to my dropbox account in a publicly-viewable folder.

Again, right now and up until about 5am Friday morning, everything should be fine. If you can't get to the HW, exams, etc., try the link above. 

Tuesday, April 29, 2014

Final exam layout

The final exam will be broken up into 5 sections. In each section, you will have a few required multiple choice questions and a choice of problems (4 problems given, solve any 2). The multiple choice questions will require some calculations, but will be much shorter than the problems. Here are the details of each section, with the corresponding sections of the book noted.

Overall, you need to do 10 problems and 12 multiple choice questions. An extensive formula sheet will be given, and you will be allowed to bring in two sheets of paper (front and back) with your own notes.

Section 1: Kinematics

  • 2.2-10 (1D motion)
  • 4.2-7 (2D motion)
  • 5.2-9, 6.2-5 (forces)

2 required multiple choice questions, choose 2 of 4 problems

Section 2: momentum and energy

  • 7.2-8 (K, work)
  • 8.2-8 (PE, consv. E)
  • 9.2-10 (p)

4 required multiple choice questions, choose 2 of 4 problems

Section 3: rotation and gravitation

  • 10.2-10 (rotation)
  • 11.2-4, 6-11 (torque, angular momentum)
  • 13.2-8 (gravitation)

1 required multiple choice question, choose 2 of 4 problems

Section 4: oscillations and waves

  • 15.2-7 (oscillations)
  • 16.2-10, 17.2-5 (waves)

2 required multiple choice questions, choose 2 of 3 problems

Section 5: fluids & thermodynamics

  • 14.2-10 (fluids)
  • 18.6-11 (temperature, heat)
  • 19.3-5, 11 (kinetic theory of gasses)

3 required multiple choice questions, choose 2 of 4 problems

Exam 4 and its solution

Here is exam 4 and its solution. Though it was an optional exam, it is a reasonable guide to what sort of questions I might ask about oscillations and gravitation on the final.

Details of the final exam coming soon.

HW6 solutions

Here you go. Final exam details and Exam 4 solutions coming shortly.

Friday, April 25, 2014

Grades updated

I've posted the grades to Blackboard again, and the lab grades should show up now. I also made a few corrections based on your feedback.

Please check carefully that all the HW sets you turned in have grades. If your lab or quiz average doesn't seem to make sense, let me know and I'll give you a detailed breakdown.

If you took the optional fourth exam on Wednesday, I'll have your graded exams back on Friday. Though very few of you took it, you chose wisely: each of you did improve your grade. (That's not to say anyone made a mistake by not taking it - for the fourth exam to really be a good call, you had to be on the borderline between grades and have one anomalously low exam grade. Not many of you fit that scenario.)

Wednesday, April 23, 2014

Grades online

I've just posted your grades on Blackboard. TL;DR check them carefully. UPDATE - the lab grades did not get uploaded somehow. I'll fix that tonight.

You should see grades for each individual HW sets from 1-5, an average lab grade, and an average quiz grade. I've dropped 1 lab, 1 homework, and 2 quizzes (note that you took quiz 5 twice). Basically, this is everything you've turned in to date, except HW6 (which is still not counted late, so most of you haven't turned it in yet). Your overall average is a fair reflection of your grade going into the final.

Please pay special attention to the HW grades  - particularly with email submissions, it is possible I've missed something. Make sure you have grades for all the HW sets you turned in, and that they match what you were handed back. Let me know if you have questions or want clarification.

The rocket competition counted for 2 labs. Out of three targets, you had 9 possible shots that counted (one practice shot per target). Here's how the grading worked:

  • 8-9 hits: 100%
  • 6-7 hits: 95%
  • 4-5 hits: 90%
  • 3 hits: 85%
  • 1-2 hits: 80%

Even if you didn't do that well in the competition, the grading was fairly generous. You all put in a lot of work leading up to the competition, and I didn't want to penalize any given group too badly for just having a bad day. Overall, we had 10 lab grades with one dropped, so there was not a lot of pressure to be honest. Tomorrow (Wed) I'll announce the winners of the competition.

Anyway: please check your grades carefully. In particular, if you have a zero for a homework set you know you turned in, let me know as soon as possible so we can figure out what happened.

Tuesday, April 22, 2014

Quiz 4 & 5 solutions

Solutions for all the quizzes are now available

Friday, April 18, 2014

Remaining schedule

Tomorrow (Friday) we'll finish up the rocket competition. Most of you still need to try the elevated targets, we'll have to work quickly and efficiently tomorrow to finish it up.

Next week, we'll cover chapters 18-20 on thermodynamics. Roughly speaking, Ch. 18 will be on Monday, Ch. 19 on Wednesday, and the parts of Ch. 20 we'll cover we will finish do on Friday. Chapter 19 will be largely familiar if you've had chemistry (ideal gas law and so on), and we will not cover all of chapter 20, so it is not as much material as it looks like.

If we can find a reasonable time to do so, and if there is enough interest, I will try to have a final exam review session during finals week.

Exam 4 is cancelled

If you were in class on Wednesday, you'll recall I cancelled exam 4. I think we've had enough exams at this point, and I'd rather spend the rest of our time on finishing the rocket competition and getting through the remaining material on thermodynamics. So, there is no exam Friday.

What this means is that the first three exams and the final will be weighted proportionally more. Specifically, that means the first three exams are worth 12.5% instead of 10%, and the final is worth 22.5% instead of 20%.

If you were relying on exam 4 to bring up your grade, please talk to me. I will give you the option of taking an optional exam 4 next week if you would rather proceed according to the original syllabus (4 exams worth 10% each and a final worth 20%).

Tuesday, April 15, 2014

Course evaluations

Please don't forget to do your course evaluations (SOI, Student Opinion of Instruction). I'll try to remember next week to set aside some time in class for you to go online and do them.

We do actually pay close attention to these surveys, and their impact is greater than you might think. Getting enough responses is critical for having meaningful data, so please do fill out the SOI surveys (you should have received an email about this). You're not wasting your time.

Monday, April 14, 2014

Exam 4

Exam 4 is this friday. Since it is only a 50 minute exam, it will be short. I will confine it to chapters 13 and 15 (gravitation and oscillations, respectively). It will be (most likely) 5 problems of which you have to solve 3.

You may safely neglect the "Einstein and gravitation", "Kepler's laws"sections as well as the "Damped simple harmonic motion" and "forced oscillations and resonance" sections for the purpose of this test, but possibly not for the final.

This week we'll talk about waves a bit more, and next week we will finish up the course talking about heat and thermodynamics.

Rocket competition

Wednesday we'll have our rocket competition after we finish going through new material. As I mentioned today, there are 3 targets you'll have to hit.

  1. over level ground
  2. hit a hole (about 0.2m in diameter and 0.5m above the floor)) in a vertically standing board
  3. hit a hole (same hole) in a board lying flat about 0.5m above the floor

You'll have three shots at each, with one practice shot. If you hit on the practice shot but miss on one of your 'real' attempts, we'll take the best 3 out of 4. Overall this will count as 2 lab grades, scaled by how many times you hit the target.

I will specify the distance to each target and its height above the floor when applicable. You'll have a marked line that you can't cross, but you can move further back, prop up your rocket, etc., so long as you don't move closer. You can use a laser pointer to align the launcher horizontally if need be. There will be a small prize for the top 3 teams.


Monday, April 7, 2014

HW6 is out

Here is HW6, it is mostly about vibrations, with a little bit on waves and gravitation thrown in. They are fairly challenging, but we'll be going over quite a few of them in class as usual. This will be your second to last homework set - planning on one more short one before dead week.

Solutions to exam 3 and HW5

Here are solutions to Exam 3 and HW5. I didn't quite get a solution typed up for #5 on HW5 (the one about the braided pipe), but you won't see anything like that on the final. I'll try to get something worked up soon. 

Sunday, March 16, 2014

Formula sheet for exam 3

Here is a draft formula sheet for exam 3. 

Saturday, March 15, 2014

HW5

Homework 5 is now ready. We will go over many of them in class on Wednesday (at least the harder ones). Nominally it is due this coming Friday, before spring break, but I will not assess any late penalties until after spring break.

That means I'd like to have it by Friday, and you probably don't want to do homework over the break anyway, but turning it in Monday after the break is fine.

Friday, March 14, 2014

HW4 solutions

HW4 solutions are available. I probably got a bit carried away with number 5 (the baseball problem). Don't read too much in to that, I was just amused by it more than anything. You won't see anything remotely like it on an exam.

UPDATE: the server seems to be having trouble, and you will probably get a 'forbidden' error when trying to download the solutions. I'll get this resolved as quickly as I can.
Fixed. Past 2am and I'm using chmod from the command line on a Linux server to fix an access problem that didn't exist yesterday. Is it 1998 again?

In any case, your HW4 solutions are ready.  

Thursday, March 13, 2014

The flow of wet and dry water

Friday we'll finish up our discussion of fluids. So far we've figured out quite a bit:

  1. hydraulics (Pascal)
  2. energy conservation in fluids without viscosity (Bernoulli)
  3. variation of pressure with depth for an ideal fluid
  4. work and forces to move fluids


We have a few things to sort out though.

  • manometers: how to measure pressure? (simple application of 3 above)
  • how do gasses differ? (density variations can't be neglected; 3 + ideal gas law)
  • what about purely rotating fluids or smoothly flowing fluids? (energy balance)
  • what about buoyancy? why does some stuff float? (3 & 4 for a foreign object in the fluid)
  • what about drag forces/viscosity and terminal velocity? (subtle ...)
  • what can we say about pressure vessels? (simple generalization of force & pressure)
I've tried for many hours, without success, to find a reasonable explanation of how viscous fluids move and the effects of turbulence without using tons of vector calculus. Fundamentally, I don't think one can do it quantitatively without some serious math, but I think I can give you a qualitative idea of what the issues are and how non-ideal fluids work.

If you are very comfortable with Cal III material, Feynman has a very nice discussion of wet & dry fluids (i.e., with and without drag/viscosity forces): Vol 2 Ch. 40 and Vol 2 Ch. 41. Fair warning, the math is difficult, and beyond what you are responsible for. But, if you're comfortable with the math and want a better idea of how fluids really works, I've not found a better description. Even if the math is too much, his discussions are worth a read - the qualitative descriptions and examples are very lucid.

Wednesday, March 12, 2014

Rocket launcher deliverable #2

Just like last week, you are basically free to do what you want during the lab work period, you just have to deliver to me the result I ask for by the end of the week. My impression so far is that you're all making very good progress, so this deliverable should be easy.

This week, I want you to tell me the following:
  • Did you find that you need to use the same rocket and turret for reliable results, or did it not matter too much?
  • Give an estimate of the variability in the launcher's range for at least 3 angles. For instance, if you do 5 launches at a given angle, what are the mean, maximum, and minimum ranges? 
  • Given the variability you find, approximately what size target do you think you could hit reliably? Ballpark answer is fine.
  • How does the actual range of the rocket compare to what you would predict without drag forces, evaluated for at least 2 angles?
  • How much kinetic energy must be lost to drag forces for each of those angles (say, a % of the launch energy)?
  • Using the example code I've given you (below), or code you've written, what drag coefficient makes your simulations match your measured data reasonably well?


Thursday, March 6, 2014

HW 4, revised due date

The remaining HW4 problems were originally planned to be due on Friday 7 March. However, I think this week we spent (arguably) too much time on the rocket launchers and not enough time on problems. As a result, I suspect that the problems you have left may seem a bit too difficult to finish by Friday.

Therefore, I'll postpone the due date of the remaining (non-daily) problems until Monday 10 March, and I'll plan to go over the HW problems in Friday's class to get you started.

Also, as it turns out, XKCD has pointed you toward one of the solutions already. The author has a degree in physics, so this is the rare case where you can actually trust a webcomic to help you with your physics homework. (Seriously, read XKCD.com and what-if.xkcd.com, they are a valuable use of your time.)

Friday, February 28, 2014

Online coding

If you're not so happy with Python, and would rather use another language for calculating your rocket's motion, I've found a site with a much larger set of available languages for coding within the browser. If you already know, say, fortran or C++, this might be much easier - you can use what language you want and not have to worry about bringing a laptop.

Rocket launchers, first deliverables

From now on, our 'labs' will be characterizing the rocket launchers and figuring out how to predict their motion. Each lab session, you'll get your launcher and tell us what sensors or equipment you might need for that session. We will not have written procedures or detailed lists of tasks, just a final goal and a set of deliverables each week.

For example, next week (by Friday), your primary deliverable is to have figured out the muzzle velocity of the launcher as well as some estimate of its uncertainty. A secondary deliverable is to sketch out how you will proceed during the following week. How you choose to proceed is up to you, I will only give advice as to whether your plans are reasonable or not, and how you might alter them if they are not reasonable.

Your deliverables will take the form of a short memo (2 pages maximum), one per group, due by the end of the day Friday March 7. Any reasonable format is accepted (hard or soft copy). This memo should contain, at least, the following key points:
  • What is the launch velocity, with an estimate of its uncertainty. Does it depend on which rocket and which turret you use?
  • How did you determine the velocity, in brief? (E.g., what sensor did you use.) Define your measure of uncertainty, or how you quantified uncertainty.
  • What are the appropriate equations of motion for your projectile, including drag? That is, what does the force depend on? (You do not need to solve the equations yet, just figure out what they are.) 
  • At launch time, you will have the ability to measure the target coordinates. Besides that and the muzzle velocity, what else do you need to know to set up your launch to hit a target?
  • What quantities can be determined experimentally ahead of time, and which will only be known once you know the target coordinates?
  • What are your potential sources of uncertainty, and how could you characterize them? A detailed plan is not necessary, just an idea.
As the week progresses, we'll discuss the finer points of your memos. All you really need is a measure of the velocity, and a rough idea of what things you're going to need to figure out over the next weeks.

HW4

Homework 4 is out. We may go through a few of these on Friday already.

Thursday, February 27, 2014

Society of Physics Students Meeting

We have an SPS meeting Wednesday, March 12th, at 6: 30 PM in Gallalee Room 200. Dr. Araujo will give a presentation (see attached flyer from the SPS).  In case you are teaching undergraduate students, please spread the word.
Thank you very much and greetings,
Claudia Mewes
(SPS faculty adviser)

Wednesday, February 26, 2014

Exam 2 solutions

Exam 2 solutions are available. You'll get the exams back at the start of Wednesday's class.

Tuesday, February 25, 2014

Tomorrow's lab

Tomorrow, we'll do one more 'regular' lab before starting with the rocket launchers. The main point is to learn how to use photogates for timing, which will be useful for characterizing your launchers. A secondary point is to verify conservation of momentum in 1D collisions.

Also: the rocket launchers just arrived yesterday, so tomorrow I'll show you what they look like and how they work. We'll need a couple of days to install the right software on the lab computers, but either this Friday or next Monday we'll get started with them.

Thursday, February 20, 2014

HW 3 solutions / Exam

HW 3 solutions are out. Reading them carefully would be a good way to study ...

As a reminder for tomorrow's exam, you are allowed 1 sheet of standard paper (front and back) with notes. You'll also be given a formula sheet that should have everything you need, a draft of which is here.

Wednesday, February 19, 2014

Class for Wed 19 Feb / upcoming exam

We'll continue our discussion of momentum a little bit, time permitting, at least as far as figuring out how to handle collisions. A larger portion of the class will be related to homework problems, which are directly relevant for the exam, and another lab on programming.

For the homework, you should be a little bothered by #6, I'll outline 2 methods to solve this one. Number 7 should be quite mysterious, and that is OK - the technique you need to solve it is related to the experimental propagation of uncertainty - if you change one variable a little bit, how do the others change? This is related to how you move along surfaces in 3D, something you are learning or have learned in Cal III.

Number 8 requires some thought - the equilibrium spacing is where U(r) is minimum, or where dU/dr = -F = 0 and the net force is zero. Find this first. The breaking point of molecule is when you exceed the maximum restoring force implied by U(r). If you find F(r) = -dU/dr and look for its maximum, this will occur for a particular r, beyond which the force binding the atoms together is exceeded and the atoms will come apart. Mathematically, that means setting dF/dr = 0 to find the maximum, that's the radius beyond which you break the molecule. Using the result for the equilibrium spacing, you can write it in terms of only n, m, and the equilibrium radius. I might have asked this question before if you are willing to dig a little.

For the exam, the format is exactly like the last time. It will likely consist of 6 problems, of which you have to solve 4. The questions will only be on work, kinetic energy, potential energy, and conservation of energy - 2 chapters in the book. You'll have a formula sheet given like last time, and can bring 1 sheet of paper of your own. I will post HW3 solutions by Thursday morning, hopefully, to help you study.

Finally, the lab: we'll continue with coding. You have two basic tasks.

1) I assert that the sum of the first n cubes of integers (sum of i^3 from i=1 to i=n) is the square of the sum of the first n integers (square of the sum of i from i=1 to i=n). Write a program that can check this for specific values of n. Print out your code and results for n=10 and n=17. Basically: sum the integers, square the sum, and compare to the sum of the cubes of integers.

2) Write and evaluate a program to calculate the range of a projectile under only the influence of gravity (no drag forces). Verify that it gives the correct result (within a few percent numerical error) for a launch speed of 25 m/s and a launch angle of 45 degrees. (You already know how to calculate the range without a drag force ...) Note that links I gave previously, and specific folders here are highly useful. Print out your code and note your results for the conditions noted.

Monday, February 17, 2014

Homework 3, number 7

This is a very tough one, and I planned on going over it in class on Wednesday. I'll sketch out the approach below.

If power is constant (which we're basically told it is for the default car), then the work done is W=P*T where T is the time over which the power is being supplied. This work done must be equal to the car's change in kinetic energy. If the car starts from rest, the work just equals the final kinetic energy, 

W =PT = (1/2)mv^2

This relates P, T, and velocity, but we don't know velocity. We do know the track length though. What we want to do is solve that for v, and integrate it to get x. Since the length of the track (x) is fixed, that will let us relate power and time by themselves.

v = sqrt(2PT/m) 
x = (integral) v dt = sqrt(4PT^3 / 3m)

The question now is what happens if we vary P by some little amount dP, what happens with T? By how much does it decrease dT? The distance x is a function of the variables P and T. It is fixed, so any change in P will have to be accompanied by a change in T to keep it constant. 

The question we're really asking then is for the function x(P,T) to remain constant, what must the rates of change in P and T be? We'd need to know the slope along the "P axis" (so dx/dP) and multiply by the tiny change in P (let's call that change DP instead of dp to keep the change straight from the derivative). We'd also need to know the same along the "T axis". Basically, the change in any function is slope times displacement for each axis, all added together. This is the same way we propagate experimental uncertainties, by the way, something I hope we will cover soon.

If the function were f(x,y), we'd approximate a small change in f due to small changes DX and DY in x and y as

Df = f(x+dx) - f(x) = (df/dx)*DX + (df/dy)*DY

In the simpler case, if you just have y(x), all this says is DY = (dy/dx)*DX. Back to the problem at hand, if we have x(P,T), 

Dx = (dx/dP)*DP + (dx/dT)*DT

Since the track length is fixed, we know Dx = 0. Thus,

(dx/dP)*DP = - (dx/dT)*DT
or   DT = -DP*(dx/dP)/(dx/dT)

Given the function above, take the derivatives with respect to P and T, divide them, and that times the change in power gives you the corresponding change in time.

I'll plan on going over this on Wednesday too.

Homework typo

I just realized that there is a typo in the due dates. Problems 3 & 4 are due today, but problems 5-10 are not due until Wednesday, 19 Feb (not today). 

Starting with Python

For tomorrow's "lab", we'll start messing around with python. Nothing fancy, just a few simple examples so you can learn to do basic calculations (like multiply stuff) and display the answer. We'll work our way up to more complicated things. If you are interested enough to mess around on your own, try the excellent tutorial here. Don't feel bad if you haven't programmed before. It will be weird at first, but you'll pick up enough to do what you need to in no time.

Sunday, February 16, 2014

Starting our project

As I mentioned on Friday, from now on we're going to stop with the usual labs and work on a project for the rest of the semester. The basic project is to characterize and simulate USB-controlled foam rocket launchers.

The ultimate goal will for you to be able to calculate numerically the flight of a realistic projectile and use this result to actually hit a target with the launcher. You will have to include drag forces and everything - using measured values of launch velocities, drag coefficients, etc. The experimental end of this will be measuring launch velocities, their variability, and trying to measure drag coefficients using the sensors we have. How to get a good measure of the drag coefficient will require some time and care. By the end, we should be able to specify a target, and you will perform the calculations and then actually hit the target.

The theoretical end of this is figuring out how to calculate things numerically. Projectile motion with drag can't be done analytically, so we'll need to learn how to simulate things. To start with, we can do this in pseudocode, as I did on Friday, just learning the appropriate algorithm for calculating trajectories numerically. Once you've got your head around how the process works, we can start with actual code. For those of you that can program, you're free to use any language you want and any methods you want. What you do has to make sense, and it has to work. For those of you that can't program, I'm going to teach you just enough Python to get the job done. We'll start learning basic python coding tomorrow; see the next post.

Friday, February 14, 2014

Scholarship/Grant opportunities

Alabama Space Grant Consortium Undergraduate Scholarship
Online Application:  https://spacegrant.net/apps/?pk=als1
Amount:  $1,000
Duration:  12 months (may renew for 1 additional year)
 
Requirements:
Must complete a short report at the end of the school year or participate in a volunteer outreach activity
Eligibility:
US Citizen
Full-time undergraduate student (Junior or Senior during Fall 2014 semester)
GPA of 3.0 or greater
Majoring in Science, Technology, Engineering, or Math
 
Alabama Space Grant Consortium Teacher Scholarship:  Undergraduate Pre-Service Teachers in Science & Mathematics
Online Application:  https://spacegrant.net/apps/?pk=als1
Amount:  $1,000 (non-renewable)
Duration:  12 months
Requirements:
Must complete a short report at the end of the school year or participate in a volunteer outreach activity
Eligibility:
US Citizen
Full-time undergraduate student
GPA of 3.0 or greater
Enrolled in a track that leads to teacher certification as a K-12 math or science teacher

Tuesday, February 11, 2014

Some notes from last class (curved paths)

These notes cover what we did in class on Monday (since it isn't in the book). We won't dwell on these results for now, but will re-use them when we revisit circular motion and when we talk about general gravitation. 

New HW is out.

Here you go. First daily problems due this coming Friday, a couple more next Monday, and the whole thing due next Wednesday.

Lab for tomorrow

Writing center hours

Not really relevant for this class, but FYI.
The UA Writing Center (Lloyd 322) announces its Spring semester hours:  Monday-Thursday, 10 am-6 pm; and Friday, 10 am-3 pm.  Walk-in hours are available at Java City/Gorgas Library, Monday-Thursday, 7 pm-9 pm.

The UA Writing Center offers free, friendly writing consultations to all UA students.  Writing Center consultants are prepared to work in numerous subject areas, and at any stage of the writing process.  For complete details, including appointment scheduling, please visit writingcenter.ua.edu.  

Exam 1 solutions

Tuesday, February 4, 2014

Women in Physics & Society of Physics Students meeting

A opportunity for stargazing with cookies and tea tomorrow night. Open to all interested.

We invite all women interested in physics & astronomy
(undergraduate and graduate students, postdocs and research assistants
associated with science & engineering) to our
Joint Meeting with SPS: Spring Meeting with Stargazing
Wednesday February 5th, 7:00-9:00 PM
223 Gallalee Building and dome on top of Gallalee Hall

Please join us for some interesting discussions with cookies and tea under the stars.
We are looking forward to seeing you
Prof. Claudia Mewes, Prof. Preethi Nair, Prof. Dawn Williams

Lab for 5 Feb

Tomorrow, we'll do a relatively simple lab on friction.

Additionally, we'll start to talk about work & energy, and figure out some better problem-solving methods that are less tedious than what you've dealt with so far. If there is time, I'll sketch out the solutions to the exam problems, but that may have to wait until Friday.

Given that I was out sick yesterday, and am not feeling great today, I am not sure when the exams will be graded. I'm hoping for Friday, but Monday at the latest.

Sunday, February 2, 2014

Formula sheet for exam 1

The formula sheet I'll give you tomorrow will look a lot like the one I used last time I taught PH125. A few things to note:

  • The exam was later last time, so there are a few things on the formula sheet we haven't covered (drag force, curved paths)
  • I will add at least the trajectory y(x) for a projectile launched from the origin (in addition to the parametric x(t) and y(t) equations already there. 
  • You can still bring in 1 sheet of your own in addition to what I provide. 
  • Don't forget to bring a calculator tomorrow. Check the batteries.

Homework 2 solutions

Here you go. I didn't get a solution finished for #8 yet, but since that required a trick that we'll not really cover in class until next week, it isn't something that would show up on the exam anyway.

Exam 1 details

As you may be aware, exam 1 is Monday during our usual class time in our usual classroom. While this is a 2 hour class period, I am designing it to be a 1 hour exam. You will have 2 hours if you need it, but if you finish in an hour (like I hope) you can just leave early.

Here are the sections from the textbook covered
  • 1D motion (2.3-2.9)
  • 2D motion (4.2-7)
  • Force & motion (5.2-9, 6.2-3, 6.5)
There will be 6 problems in total, of which you must complete 4. If you do more than 4, I will grade them all and use the best 4 (but try to get 4 done well first). There will be a formula sheet provided with all the basic formulas and any numerical constants you will need, and you can bring in one sheet of 8.5x11in paper of your own with notes, etc. What you put on the one sheet you bring in is entirely up to you, and you can use the front & back of the sheet.
There will be heavy partial credit on the exam, so show all your work and be as clear as possible about what you are trying to do.
Good things to study? Old homework and exams, and the homework problems I've given you so far. The exam questions will be easier than the homework I've given you, so don't worry too much. Doing the example problems in the book, or the odd numbered end of chapter problems is also good (so you can see the answer when you're done).
I'll be posting HW2 solutions shortly.

Wednesday, January 29, 2014

HW2 problem 5

On problem 5, I failed to specify the coefficient of friction between block b and the flat surface. Take it to be 0.20.

Also note that the ramp can be treated as frictionless, only worry about friction for the flat surface.

The Snowpocalypse continues

We'll have to play this by ear, but here's the current plan:

  • HW due Friday by midnight, presuming UA is open Friday. 
  • Friday's class: work homework problems, review for the exam. 
  • Exam on Monday, but taking only ~50 minutes. We'll spend the rest of the class period working problems and discussing new material.

Given that it is supposed to be in the high 40's tomorrow at least, I fully expect we'll have class on Friday. I don't think we'll know whether UA will be open tomorrow (Thurs) until ~4pm today.  UA is closed Thursday. Presuming we have class on Friday, we'll spend most of that time working on homework and getting you ready for an exam on Monday.

Tuesday, January 28, 2014

Snowpocalypse 2014

I'm going to make a wild leap and assume classes will be held tomorrow.

On the outside chance that they are not, the HW due date and exam will shift by one class. Specifically, if there are no classes tomorrow, the HW will be due on Friday and the exam will move to Monday. Again, so long as classes are still on tomorrow, the HW is due Wednesday and the exam will be Friday.

Right. Better get back to shoveling my car out of the snow drifts so I can stock up on bread and milk.


Wednesday's lab

Here you go - just like one of the problems we worked out in class today.

Monday, January 27, 2014

Speaking of Wolfram Alpha

You'd be surprised what it will answer. It knows physics too, not just math ...

Using Wolfram Alpha

It can be a bit tricky to get Wofram Alpha to understand what you want. A couple of key tricks (and I'll give examples) to make it easier:

Thursday, January 23, 2014

Field trip opportunity. Seriously.

I would like to point out an opportunity for a 3 week field trip to Yellowstone for under-represented students in the sciences.

More info can be found here:

http://physics.ua.edu/news/Yellowstone_FieldCourse_Brochure.pdf

The deadline to apply is 1 Feb 2014. The application is on the last page of the brochure linked above

Wednesday, January 22, 2014

Homework 2

Homework 2 is out. You do have one daily problem due Friday, but it (should be) relatively quick. Some of the problems are more involved than last week, so don't put off the rest of the problems ... we will do at least a few of them in class on Mon & Wed next week.

[Hint on the first daily problem: it is easy to write down the equation of motion for either car. The tricky part is making sure that their time coordinates agree. You might call t=0 the moment when the cop starts moving, and say the other car passed it at t=-2 seconds (time can be negative, that's fine). You could also call t=0 the moment the car passes the cop, and write the cop's position in such a way that it is 0 after 2 seconds, and following accelerated motion after that. Either way describes the same situation and the same physics, the math is slightly easier for one of the choices.]

Tuesday, January 21, 2014

Homework 1 solutions

HW1 solutions are available. Let me know if you notice any errors.

Tomorrow's lab

Here is the background reading and procedure. Please read it before tomorrow's class. You can print it when you arrive, no need to print it at home. Depending on how the time goes, we may finish the prep questions and writeup on Friday.

You might also find this derivation of linear regression interesting, but it is not required reading.

Monday, January 20, 2014

Next HW

Owing to the long weekend, I'm delaying putting out the second HW until Wednesday. Seems more realistic. I should have HW1 solutions out at that time as well. 

Sunday, January 19, 2014

Submitting homework

The first homework submission went very well I thought. I've been accepting email homework quite a while now, and this was probably the easiest first homework submission I've had.

That being said, here are a couple of suggestions that will make the process easier for me:

Friday, January 17, 2014

In case you are interested

UA Society of Physics Students First Meeting of the Semester!

When: 6:30 PM Wednesday January 22nd

Where: Gallalee Room 200

What:

  • Discuss semester activities 
  • Watch The PHD Movie

Help Desk

The class may seem difficult so far. It should, we are starting off with pretty tough pace. I'm not going to promise that it will slow down or get a little easier, but I think it will. In any case, at this point trying to finish up the first homework set you may be wanting a little extra help, and we've got you covered.

All the intro physics TAs pool their office hours together to staff our physics Help Desk. You can find a schedule of available TAs and which room they will be in here. You can pick any time slot that is staffed and just show up to the relevant room, so you have lots of chances to go and ask questions.

(You can also always stick around after class and ask me questions, or come to my office hours too.)

Thursday, January 16, 2014

Exam duration / syllabus confusion

The syllabus is not totally clear as to how long the exams are. The in-class exams will all be 50 minutes long, no matter what day they occur on. 

There is some confusion because my original (internal) schedule had all the exams on M or W, presupposing rather long exams. After rethinking it a bit, the exams didn't end up coming at natural logical breaks in the course material, and of course long exams just suck. At that point, I moved the exam dates around, putting most of the exams on Friday instead (so long as there was a natural conceptual break in the material), but forgot to update the syllabus. (One exam remains on a Monday because the preceding and following Fridays would make for awkward exam coverage.)

What the syllabus should say is that all four "hour" exams will designed to take 50 minutes, independent of what day they are on. For the one exam scheduled on Monday, you will still have a 50 minute exam, not a 110 minute exam. We will probably use the remainder of the 110 minute class period to review or do a short lab.

Solutions for quiz 1, 15 Jan daily problem

Tuesday, January 14, 2014

Monday, January 13, 2014

Lab 1 / Wed 15 Jan

On Wednesday, we'll do a lab on uncertainty analysis.

You don't need to print this out, just read it before Wednesday's class. You can print what you need in the classroom when you arrive. Please just print one copy per group, you'll be working in groups of 3-4.

Wednesday, January 8, 2014

Webassign / Textbook

Some of you have been wondering, and I wasn't crystal clear about it - you don't need a WebAssign code with your textbook. Your homework is purely pencil & paper type stuff.

If you already got a WebAssign code with your book, the chances are extremely high that someone in one of the PH105 sections could use it, or you could just try to exchange it.  

Reading for Friday

For Friday, the reading is Halliday, Resnick, and Walker Ch. 2 (motion along a straight line). You should also skim Ch. 1 (physics & measurement) to make sure it all makes sense - most of it should be review I suspect, and most of those topics will come up naturally as the semester progresses.

If you're looking for a little something more, you can check out the Fenyman Lectures on Physics, specifically Volume 1, Ch. 8. Much of the supplemental reading I'll post will be from the Feynman lectures (called 'FLP' on the schedule).

Tuesday, January 7, 2014

Homework 1

Here is your first homework set. Note that there are multiple due dates - you have two problems due at the start of class 13 Jan, one due at the start of class on 15 Jan, and the rest are due by the end of the day on 17 Jan. Also note that I would like you to use the problem template format when turning in homework.

Course intro slides

Here are the slides I'll use at the start of the first class to go over the course format, etc.

Friday, January 3, 2014

Welcome to PH125 / Spring 2014

This is where you will find all the information you need for PH125 this semester. If you are in to such things, subscribe to the atom feed, it will make things easier. 

Be sure to note the handy links on the left sidebar. In particular, note that all course content from Spring 2009 is available, including old homework and solutions. The Feynman Lectures on Physics are also a great resource in addition to your textbook.

Your syllabus is already online for your perusal; read it carefully!