So, here's how it is. Thanks to weather-related FAIL today, I'm stuck in Miami for another day. I had hoped to get back late tonight, go grab the exams tomorrow morning, and have them graded and back by Tuesday.
At the earliest, I'll now be back in town Saturday afternoon. If all goes well, I can still get the exams graded by Tuesday ... I will try. At the very least, I will get you solutions to the exam by Tuesday, one way or another. I really did choose all the problems there for a reason, and I want you to see how they are worked out while the ideas are still fresh in your mind.
Friday, February 27, 2009
For Tuesday ...
All you need to do for Tuesday is to have formed your groups for the ballistics project, we will start work on this in earnest next week.
I'll post some details about the project and the tasks you'll have to perform this weekend. The first thing we will do is work on measuring the drag force on our rockets, and how to accurately model its trajectory ... the actual rocket launchers should be here on Tuesday.
I'll post some details about the project and the tasks you'll have to perform this weekend. The first thing we will do is work on measuring the drag force on our rockets, and how to accurately model its trajectory ... the actual rocket launchers should be here on Tuesday.
Wednesday, February 25, 2009
Stupid tricks for your TI-89
A lot of you seem to have TI-89's or related instruments ... here's a nice how-to guide.
Formula sheet
Well, if you aren't going to get some rest, you can peruse the formula sheet for the exam.
Subject to small changes / additions as I find typos & omissions.
Subject to small changes / additions as I find typos & omissions.
Get some rest.
Seriously, cramming isn't going to help, there is nothing to memorize. You need really only need two things for the exam:
Get a decent night's sleep so you're at maximum cleverness tomorrow. Most of the problems have subtleties in them that require careful thinking, and the math will get ugly very fast if you miss little things here and there. You will be tested on problem solving, keep that in mind.
If you were able to follow all of the problems we did on Tuesday, you will be in good shape for the exam.
- conservation and defnitions of energy
- conservation and definitions of momentum
Get a decent night's sleep so you're at maximum cleverness tomorrow. Most of the problems have subtleties in them that require careful thinking, and the math will get ugly very fast if you miss little things here and there. You will be tested on problem solving, keep that in mind.
If you were able to follow all of the problems we did on Tuesday, you will be in good shape for the exam.
Tuesday, February 24, 2009
Tuesday's class
Today, we have really only two tasks:
(1) review for the exam on Thursday
(2) get started on our projectile guidance system
The first part will basically be problem solving - working out some of the current homework problems, and a few extras.
The second part will largely be learning how to numerically calculate ballistic trajectories in the presence of resistive forces, i.e., drag. We have to get this out of the way before we start building and measuring things. Part of this will also include organization - forming teams and dividing tasks, defining the scope and details of our little ballistics project.
Finally: in light of the exam on Thursday, there will be no recitation this Friday. (Also, I am out of town on Friday.)
(1) review for the exam on Thursday
(2) get started on our projectile guidance system
The first part will basically be problem solving - working out some of the current homework problems, and a few extras.
The second part will largely be learning how to numerically calculate ballistic trajectories in the presence of resistive forces, i.e., drag. We have to get this out of the way before we start building and measuring things. Part of this will also include organization - forming teams and dividing tasks, defining the scope and details of our little ballistics project.
Finally: in light of the exam on Thursday, there will be no recitation this Friday. (Also, I am out of town on Friday.)
Homework 6 solutions
Here they are, a bit more than half complete right now.
I'll try to get the rest of the solutions finished by some time Tues afternoon.
I'll try to get the rest of the solutions finished by some time Tues afternoon.
Monday, February 23, 2009
Exam II
Just FYI ... the rules for Thursday's exam are basically like those for the previous exam.
You will have a choice of problems, though a bit less choice this time. You can bring in one formula sheet with whatever you like on it, I will provide the basic formulas and numbers needed.
The exam will nominally cover chapters 7-9, though I think it is clear that the material thus far is somewhat cumulative. Details on precisely what sections are covered (and which ones aren't) will follow later today.
I should have HW6 solutions up before tomorrow's class to aid in studying. Your latest homework set is also meant to get you solving the sort of problems I'll ask on the exam. Yes, it will be harder than the last one, but nothing you can't handle, and nothing we haven't gone over in class. Really, the only way to study for this one is to work problems.
You will have a choice of problems, though a bit less choice this time. You can bring in one formula sheet with whatever you like on it, I will provide the basic formulas and numbers needed.
The exam will nominally cover chapters 7-9, though I think it is clear that the material thus far is somewhat cumulative. Details on precisely what sections are covered (and which ones aren't) will follow later today.
I should have HW6 solutions up before tomorrow's class to aid in studying. Your latest homework set is also meant to get you solving the sort of problems I'll ask on the exam. Yes, it will be harder than the last one, but nothing you can't handle, and nothing we haven't gone over in class. Really, the only way to study for this one is to work problems.
Sunday, February 22, 2009
HW 5 solutions
The solutions to Homework 5 are out.
Just for 'fun,' I included code snippets in various languages to solve the last problem, in which you needed to sum the harmonic series over 75 terms. Actually, I wrote quick versions in several languages, such was the depth of my procrastination. Represented are
(In particular, my postscript solution could be fancied up quite a bit for prettier output. The bash script is also a bit cheap and approximate, since one can only use integers.)
Just for 'fun,' I included code snippets in various languages to solve the last problem, in which you needed to sum the harmonic series over 75 terms. Actually, I wrote quick versions in several languages, such was the depth of my procrastination. Represented are
- C (iterative and recursive solutions)
- Pascal
- Perl
- LISP
- Python
- Java
- shell (bash) script
- Postscript
- Fortran
(In particular, my postscript solution could be fancied up quite a bit for prettier output. The bash script is also a bit cheap and approximate, since one can only use integers.)
HW 7 is out
Here you go.
Differences this week:
Differences this week:
- all problems are due Thursday, just before the exam
- you do not need to use the template this time
- consider this an exam review ...
Midterm grades
Except for the very last lab (momentum) and homework set (#6), all grades should now be up on Moodle.
I have included a separate field for your midterm grade, which was calculated by dropping 1 lab, 1 homework, and 1 quiz. The relative percentages are in the syllabus for the curious.
Midterm grades are due Monday evening, so let me know ASAP if you see any irregularities or have any questions.
I have included a separate field for your midterm grade, which was calculated by dropping 1 lab, 1 homework, and 1 quiz. The relative percentages are in the syllabus for the curious.
Midterm grades are due Monday evening, so let me know ASAP if you see any irregularities or have any questions.
Thursday, February 19, 2009
Thursday's lab
We will take two carts, and run them into each other.
Also: we will spend time setting up a few of the homework problems. You aren't putting them off, right?
Also: we will spend time setting up a few of the homework problems. You aren't putting them off, right?
Wednesday, February 18, 2009
Typo 9.45
There is a typo in the numerical answer in the back of the book. It should be +45, not -45.
Draw the initial velocity vectors, and it will be clear why (I think) even if your math doesn't jive.
Draw the initial velocity vectors, and it will be clear why (I think) even if your math doesn't jive.
Random homework hints
9.8 Of course, you know the liquid density owing to the fact that you know the mass and volume when the can is filled. This is enough to calculate the liquid mass when the can is filled to a depth x. It is advisable to plot the resulting center of mass versus x.
9.15 You can easily find the velocity of the projectile at the top of the trajectory. At that point, apply conservation of momentum. If the falling particle has no initial velocity ...
9.45 Don't overthink this one. Conservation of momentum before and after along x and y axes. Symmetry is useful.
9.48 Both energy and momentum must be conserved, right?
9.15 You can easily find the velocity of the projectile at the top of the trajectory. At that point, apply conservation of momentum. If the falling particle has no initial velocity ...
9.45 Don't overthink this one. Conservation of momentum before and after along x and y axes. Symmetry is useful.
9.48 Both energy and momentum must be conserved, right?
Grading
I'm still a bit behind on grading, but nearly caught up.
Moodle how has quizzes 1-7 and homework sets 1-4.
Outstanding things are homework set 5, and your last two labs. I'll have these posted Wednesday or Thursday, which will put everything up to date.
The overall grades you see in Moodle are artificially low, in that I have not (yet) dropped any quizzes, labs, or homework sets. Consider the displayed total a worst-case scenario!
Midterm grades are due this coming Monday. By this Friday, I will have accurate mid-term grades available on Moodle for you to review ... so you can let me know if anything looks incorrect before Monday's deadline.
Moodle how has quizzes 1-7 and homework sets 1-4.
Outstanding things are homework set 5, and your last two labs. I'll have these posted Wednesday or Thursday, which will put everything up to date.
The overall grades you see in Moodle are artificially low, in that I have not (yet) dropped any quizzes, labs, or homework sets. Consider the displayed total a worst-case scenario!
Midterm grades are due this coming Monday. By this Friday, I will have accurate mid-term grades available on Moodle for you to review ... so you can let me know if anything looks incorrect before Monday's deadline.
Monday, February 16, 2009
Homework #6
This week, we'll have a bit of a change in the homework procedure.
Rather than have problems due every day, I will let you turn in all problems at the end of the day on Friday. Do not take this freedom lightly: it is unlikely you will be able to complete all of these problems in a single night (e.g., Friday night). You will need to work on this throughout the remainder of the week to have hopes of finishing all the problems.
Anyway: this week's homework consists of the following problems from your textbook: 9.5, 9.8, 9.15, 9.33, 9.45, 9.48, 9.53, 9.59, and 9.68.
A more formal-looking version of the homework is here.
Rather than have problems due every day, I will let you turn in all problems at the end of the day on Friday. Do not take this freedom lightly: it is unlikely you will be able to complete all of these problems in a single night (e.g., Friday night). You will need to work on this throughout the remainder of the week to have hopes of finishing all the problems.
Anyway: this week's homework consists of the following problems from your textbook: 9.5, 9.8, 9.15, 9.33, 9.45, 9.48, 9.53, 9.59, and 9.68.
A more formal-looking version of the homework is here.
Homework 5, #7
By the way, here are a few code-based solutions that you submitted to homework 5 problem #7. Quite a variety - Fortran, C/C++, and Python are all represented.
My own (hastily-composed) version is here, in standard C. It should compile with vanilla gcc. It takes a command-line argument N, where N is how many terms of the harmonic series to evaluate. For "fun" I also included code (commented out) to calculate the same sum recursively.
For reference, here is the source of the problem (Car Talk), here is their answer, which employs the Euler–Mascheroni constant.
My own (hastily-composed) version is here, in standard C. It should compile with vanilla gcc. It takes a command-line argument N, where N is how many terms of the harmonic series to evaluate. For "fun" I also included code (commented out) to calculate the same sum recursively.
For reference, here is the source of the problem (Car Talk), here is their answer, which employs the Euler–Mascheroni constant.
Next HW
I am a bit behind on getting this week's homework set out ...
There will be a new homework set posted later today. Since I am late in getting it out, there will be no problems due until this Wednesday evening.
Basically: no homework due tomorrow ... but don't get too comfortable :-)
There will be a new homework set posted later today. Since I am late in getting it out, there will be no problems due until this Wednesday evening.
Basically: no homework due tomorrow ... but don't get too comfortable :-)
Thursday, February 12, 2009
Friday's class
Tomorrow: yet more on potential energy ... we'll try to tie up the loose ends and put things together so we can start in with momentum next week. Finally, things will start colliding.
For example.
I have gotten a bit behind on the grading at the moment, and am working to rectify that right now. Tomorrow, you should get back a great deal of homework and a couple of lab reports. I'm trying to keep the turnaround at 2-3 days, but it has slipped a bit this week.
For example.
I have gotten a bit behind on the grading at the moment, and am working to rectify that right now. Tomorrow, you should get back a great deal of homework and a couple of lab reports. I'm trying to keep the turnaround at 2-3 days, but it has slipped a bit this week.
HW Clarification
A question from one of you:
Correct on both accounts - if the problem just asks for a number in one part, no symbolic solution is necessary. Since the problem asks for U(x), that is sufficient for a sketch.
Is a symbolic solution necessary for the simple parts of 8.41
such as part a? Also, our b part should serve as a sketch shouldn't it?
Correct on both accounts - if the problem just asks for a number in one part, no symbolic solution is necessary. Since the problem asks for U(x), that is sufficient for a sketch.
Thursday's class
FYI: schedule change.
There are scheduling difficulties with the lab we had planned for today (nothing interesting, merely difficult), so we will instead focus on problem solving for a good chunk of the class. Part of that will be setting up this week's homework problems.
I will first go into some more detail on potential energy and conservation of energy, but will try to confine that to 45min or so ... such that most of the time will be spent figuring out how to use the new ideas.
There are scheduling difficulties with the lab we had planned for today (nothing interesting, merely difficult), so we will instead focus on problem solving for a good chunk of the class. Part of that will be setting up this week's homework problems.
I will first go into some more detail on potential energy and conservation of energy, but will try to confine that to 45min or so ... such that most of the time will be spent figuring out how to use the new ideas.
Wednesday, February 11, 2009
Thursday's homework
Change of plans (for the better):
Let's have tomorrow's homework due at the end of the day rather than at the beginning of class, so you have a chance to ask questions if need be.
Let's have tomorrow's homework due at the end of the day rather than at the beginning of class, so you have a chance to ask questions if need be.
Monday, February 9, 2009
Lab for Tues 10 Feb 2009
Tomorrow, we'll measure the coefficient of restitution.
Basically, this is a measure of how velocity is lost by an object due to impact with another object. The Wikipedia has some (limited) background information on why this is a useful metric.
(Baseball-related paper ... Rockies fans take note.)
Basically, this is a measure of how velocity is lost by an object due to impact with another object. The Wikipedia has some (limited) background information on why this is a useful metric.
(Baseball-related paper ... Rockies fans take note.)
Exam 1 solutions
UPDATE: the solutions are now complete, but probably require some proofreading yet. The link below is still correct.
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I am busy making up the solutions, here is the progress so far.
I'll be updating the solutions throughout the day, and will post here when they are complete. The filename will not change, so the above link will remain useful.
---------
I am busy making up the solutions, here is the progress so far.
I'll be updating the solutions throughout the day, and will post here when they are complete. The filename will not change, so the above link will remain useful.
Problem set 5
Problem set 5 is now out.
Since it is coming out a bit late, tomorrow's problems are not due until the end of the day (as opposed to at the beginning of class). I'll set those two problems up in class to help you get started.
Solutions to HW4 are now out, and exam solutions will follow later today.
Since it is coming out a bit late, tomorrow's problems are not due until the end of the day (as opposed to at the beginning of class). I'll set those two problems up in class to help you get started.
Solutions to HW4 are now out, and exam solutions will follow later today.
Saturday, February 7, 2009
Quiz 5 and 6 solutions
Quizzes 5 and 6 are out now, along with their solutions.
A new problem set will be following shortly, which will have some problems due on Tuesday. You can also expect some problem set solutions over the weekend.
A new problem set will be following shortly, which will have some problems due on Tuesday. You can also expect some problem set solutions over the weekend.
Thursday, February 5, 2009
Physics of the Death Star
We won't cover gravitation until just before spring break ... but file this away for later.
Another great blog full of neat physics posts, highly recommended.
Another great blog full of neat physics posts, highly recommended.
This Friday's homework
By the way: typo on the homework.
Friday's problems are due at the end of the day, i.e., 1 minute before midnight, not at the beginning of class as the problem set claims.
In other news, we will begin studying work & energy tomorrow (Ch. 7). Reading Ch. 7 before class tomorrow, or at least skimming it is a Good Idea.
By the way: I tried to choose a textbook this semester that would make the reading less ... painful. I don't point out each day what you should be reading, mainly because I think it is sort of obvious from the schedule - if we start Ch. 7 tomorrow, you should read Ch. 7 for tomorrow. I am naively assuming that you do the reading each time (!), and that the more studious of you are working through the example problems on your own.
Here's a good little post on physics textbooks, FWIW. I have nearly written my own book for ph102 out of sheer frustration; the fact that I have not even thought of this for ph125 speaks to my high regard for the classic H&R text. YMMV.
Friday's problems are due at the end of the day, i.e., 1 minute before midnight, not at the beginning of class as the problem set claims.
In other news, we will begin studying work & energy tomorrow (Ch. 7). Reading Ch. 7 before class tomorrow, or at least skimming it is a Good Idea.
By the way: I tried to choose a textbook this semester that would make the reading less ... painful. I don't point out each day what you should be reading, mainly because I think it is sort of obvious from the schedule - if we start Ch. 7 tomorrow, you should read Ch. 7 for tomorrow. I am naively assuming that you do the reading each time (!), and that the more studious of you are working through the example problems on your own.
Here's a good little post on physics textbooks, FWIW. I have nearly written my own book for ph102 out of sheer frustration; the fact that I have not even thought of this for ph125 speaks to my high regard for the classic H&R text. YMMV.
Wednesday, February 4, 2009
Have free time?
Our IT guy over here in MINT is looking for a gopher to install software, swap out computer hardware, etc. Anyone looking for a few hours a week of work and need a little cash?
Exams are graded
Your exams are graded, and the results are on moodle (instructions). I have only made one pass at grading, so I will have to double check things yet. Caveat lector.
The average was an astounding 89.7 (std. dev. 5.8). I did go a little easy on the grading, but not that easy - you did very well, and I was pleasantly surprised.
Below are some nerdy plots for you (click for larger version): a histogram of sorts; the percentage of you choosing each problem; and of those that chose each problem, the average score. We'll discuss briefly on Thursday what I think they're telling us, if anything.
Hard to draw too many conclusions when the average is high and the standard deviation is low ...
The average was an astounding 89.7 (std. dev. 5.8). I did go a little easy on the grading, but not that easy - you did very well, and I was pleasantly surprised.
Below are some nerdy plots for you (click for larger version): a histogram of sorts; the percentage of you choosing each problem; and of those that chose each problem, the average score. We'll discuss briefly on Thursday what I think they're telling us, if anything.
Hard to draw too many conclusions when the average is high and the standard deviation is low ...
Tuesday, February 3, 2009
HW4 / Exam
Here is your fourth homework, with problems due this Thursday and Friday.
Part of the homework is to solve exam problems you did not choose. For that, you will need a copy of the exam.
It would be very, very nice if you used the 2-page problem template. I can print them for you if necessary.
Part of the homework is to solve exam problems you did not choose. For that, you will need a copy of the exam.
It would be very, very nice if you used the 2-page problem template. I can print them for you if necessary.
Monday, February 2, 2009
Draft of the exam formula sheet
Find it here.
It still needs proofreading, but not much should change. This is basically what you'll get tomorrow.
It still needs proofreading, but not much should change. This is basically what you'll get tomorrow.
More practice problems
I'm not saying you should do all of these tonight, but here are some problems from each chapter I think are worth glancing at. If you know how to do one already, skip it and move in. If you're not sure ... give it a try. These are all odd-numbered problems, so you have the answers in the back of your book.
Ch. 1
not on the exam.
Ch. 2
15, 29, 45, 51, 109
Ch. 3
there are no questions on the exam specifically from Ch. 3, but here are some vector practice problems that are useful: 35, 39, 43
Ch. 4
13, 25, 27, 35, 41, 61, 65
Ch. 5
19, 43, 51, 53, 59, 101
Ch. 6
17, 23, 27, 31, 41, 81, 109
I'll do some of these at the review session tonight - if you have time, glance through these and have some suggestions for which ones I should do on the board.
Ch. 1
not on the exam.
Ch. 2
15, 29, 45, 51, 109
Ch. 3
there are no questions on the exam specifically from Ch. 3, but here are some vector practice problems that are useful: 35, 39, 43
Ch. 4
13, 25, 27, 35, 41, 61, 65
Ch. 5
19, 43, 51, 53, 59, 101
Ch. 6
17, 23, 27, 31, 41, 81, 109
I'll do some of these at the review session tonight - if you have time, glance through these and have some suggestions for which ones I should do on the board.
Reminder: review session tonight 7:15pm
Tonight, 7:15pm, 203 Gallalee hall. Come armed with questions. I'll come with some additional practice problems to work out, similar to what will be on the exam.
Remember my phone number in case for some reason the building gets locked up early ... I will be checking outside around 7:15 as well.
Remember my phone number in case for some reason the building gets locked up early ... I will be checking outside around 7:15 as well.
Checking grades online
I how have a system set up so you can log in and see your grades.
1) go here: http://faculty.mint.ua.edu/~pleclair/moodle/
2) Click on "Physics 125 / Dr. LeClair"
3) Then, to log in to the system:
From this page, you can access your grades. You should see a link for "Grades" on the left-hand side of the page, about halfway down, under "Administration." For that matter, you can change your profile, create a little blog or discussion board, or all sorts of other things.
Any feedback you have on this system is helpful. Let me know if it works ... and I should have more grades entered early next week. Right now, all four quizzes and the first two lab and homework grades are there.
1) go here: http://faculty.mint.ua.edu/~pleclair/moodle/
2) Click on "Physics 125 / Dr. LeClair"
3) Then, to log in to the system:
- your username is same as your bama email address
- Thus, if your bama email is "jdingus@bama.ua.edu" your username is "jdingus"
- your password is the last four digits of your CWID. You can change the password if you like after logging in.
From this page, you can access your grades. You should see a link for "Grades" on the left-hand side of the page, about halfway down, under "Administration." For that matter, you can change your profile, create a little blog or discussion board, or all sorts of other things.
Any feedback you have on this system is helpful. Let me know if it works ... and I should have more grades entered early next week. Right now, all four quizzes and the first two lab and homework grades are there.
Sunday, February 1, 2009
Practice Exam solutions
UPDATE: full solutions are now up. (The filename has not changed, I just updated the contents.)
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Here are the solutions to about the first half of the practice problems. They are a bit terse, which reflects my haste this evening/morning, but I think they should be understandable.* With luck, complete solutions will follow tomorrow in the early afternoon.
These problems are not as diverse a set as I would have liked,** but I think if you can get through all of these fairly quickly without much trouble, you will be fine on the exam. Another good thing to do is study the example problems in your text.
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* Most likely, I am just too long-winded in my normal solutions, and these are fine ... feel free to weigh in on this point, since I am writing these things for you.
** On the other hand, at least one of these practice problems will show up verbatim on the exam. Really.
------
Here are the solutions to about the first half of the practice problems. They are a bit terse, which reflects my haste this evening/morning, but I think they should be understandable.* With luck, complete solutions will follow tomorrow in the early afternoon.
These problems are not as diverse a set as I would have liked,** but I think if you can get through all of these fairly quickly without much trouble, you will be fine on the exam. Another good thing to do is study the example problems in your text.
------------
* Most likely, I am just too long-winded in my normal solutions, and these are fine ... feel free to weigh in on this point, since I am writing these things for you.
** On the other hand, at least one of these practice problems will show up verbatim on the exam. Really.
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