tag:blogger.com,1999:blog-17307454690087298502024-02-21T11:48:29.731-06:00Physics 125Spring 2014, University of Alabamapleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.comBlogger265125tag:blogger.com,1999:blog-1730745469008729850.post-8771844729080216942014-05-07T01:12:00.001-05:002014-05-07T01:12:15.158-05:00Final grades<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
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%.<br />
<br />
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.<br />
<br />
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.<br />
<br />
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).<br />
<br />
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. </div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-60734590655650040142014-05-06T10:14:00.003-05:002014-05-06T10:14:39.251-05:00Final grades are not ready yet<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="color: #222222; font-family: arial; font-size: small;">
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.</div>
<div style="color: #222222; font-family: arial; font-size: small;">
<br /></div>
<div style="color: #222222; font-family: arial; font-size: small;">
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.</div>
</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-60398842080325661242014-05-01T17:15:00.003-05:002014-05-01T17:15:41.345-05:00IMPORTANT NOTICE<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
<div style="text-align: left;">
<span style="font-size: x-small;">(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.)</span></div>
<br />
This should not be a problem, but <i>just in case</i> you find dead links, I'm copying all of my old PH101, PH105, and PH125 material to <a href="https://www.dropbox.com/sh/db0v1xev7si1ufl/LCHo3JTxCf">my dropbox account in a publicly-viewable folder</a>.<br />
<br />
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. </div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-44958470420360439052014-04-29T12:25:00.000-05:002014-04-29T12:25:19.712-05:00Final exam layout<div dir="ltr" style="text-align: left;" trbidi="on">
The final exam will be broken up into 5 sections. In each section, you will have a few <b>required</b> 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.<br />
<br />
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.<br />
<b><br /></b>
<b>Section 1: Kinematics</b><br />
<br />
<ul style="text-align: left;">
<li>2.2-10 (1D motion)</li>
<li>4.2-7 (2D motion)</li>
<li>5.2-9, 6.2-5 (forces)</li>
</ul>
<br />
2 required multiple choice questions, choose 2 of 4 problems<br />
<b><br /></b>
<b>Section 2: momentum and energy</b><br />
<br />
<ul style="text-align: left;">
<li>7.2-8 (K, work)</li>
<li>8.2-8 (PE, consv. E)</li>
<li>9.2-10 (p)</li>
</ul>
<br />
4 required multiple choice questions, choose 2 of 4 problems<br />
<br />
<b>Section 3: rotation and gravitation</b><br />
<br />
<ul style="text-align: left;">
<li>10.2-10 (rotation)</li>
<li>11.2-4, 6-11 (torque, angular momentum)</li>
<li>13.2-8 (gravitation)</li>
</ul>
<br />
1 required multiple choice question, choose 2 of 4 problems<br />
<br />
<b>Section 4: oscillations and waves</b><br />
<br />
<ul style="text-align: left;">
<li>15.2-7 (oscillations)</li>
<li>16.2-10, 17.2-5 (waves)</li>
</ul>
<br />
2 required multiple choice questions, choose 2 of 3 problems<br />
<br />
<b>Section 5: fluids & thermodynamics</b><br />
<br />
<ul style="text-align: left;">
<li>14.2-10 (fluids)</li>
<li>18.6-11 (temperature, heat)</li>
<li>19.3-5, 11 (kinetic theory of gasses)</li>
</ul>
<br />
3 required multiple choice questions, choose 2 of 4 problems</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-83210154796040985242014-04-29T12:04:00.004-05:002014-04-29T12:04:41.012-05:00Exam 4 and its solution<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="http://faculty.mint.ua.edu/~pleclair/ph125/Exams/">Here is exam 4 and its solution</a>. 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.<br />
<br />
Details of the final exam coming soon.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-56419902195872368522014-04-29T10:34:00.003-05:002014-04-29T10:34:29.664-05:00HW6 solutions<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="http://faculty.mint.ua.edu/~pleclair/ph125/Homework/HW6_11Apr14-SOLN.pdf">Here you go</a>. Final exam details and Exam 4 solutions coming shortly.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-5843378952302172212014-04-25T00:24:00.005-05:002014-04-25T00:24:50.164-05:00Grades updated<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
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.<br />
<br />
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 <i>and </i>have one anomalously low exam grade. Not many of you fit that scenario.)</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-64999512707964433982014-04-23T01:13:00.000-05:002014-04-23T11:25:27.090-05:00Grades online<div dir="ltr" style="text-align: left;" trbidi="on">
I've just posted your grades on Blackboard. TL;DR check them carefully. <b>UPDATE</b> - the lab grades did not get uploaded somehow. I'll fix that tonight.<br />
<br />
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.<br />
<br />
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.<br />
<br />
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:<br />
<br />
<ul style="text-align: left;">
<li>8-9 hits: 100%</li>
<li>6-7 hits: 95%</li>
<li>4-5 hits: 90%</li>
<li>3 hits: 85%</li>
<li>1-2 hits: 80%</li>
</ul>
<br />
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.<br />
<br />
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.<br />
<br /></div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-65673951608367358912014-04-22T22:55:00.000-05:002014-04-22T22:55:02.390-05:00Quiz 4 & 5 solutions<div dir="ltr" style="text-align: left;" trbidi="on">
Solutions for all the quizzes are <a href="http://faculty.mint.ua.edu/~pleclair/ph125/Quizzes/">now available</a>. </div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-12984558192559619402014-04-18T00:42:00.000-05:002014-04-18T00:42:14.250-05:00Remaining schedule<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
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.<br />
<br />
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.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-70239994348878665722014-04-18T00:38:00.002-05:002014-04-18T00:38:30.060-05:00Exam 4 is cancelled<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
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%.<br />
<br />
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%).</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-50457832503924126762014-04-15T23:14:00.003-05:002014-04-15T23:14:39.258-05:00Course evaluations<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
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.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-22908563192717382112014-04-14T14:39:00.003-05:002014-04-14T14:39:56.396-05:00Exam 4<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
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.<br />
<br />
This week we'll talk about waves a bit more, and next week we will finish up the course talking about heat and thermodynamics.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-79416694361811094212014-04-14T14:37:00.001-05:002014-04-14T14:37:15.708-05:00Rocket competition<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
<br />
<ol style="text-align: left;">
<li>over level ground</li>
<li>hit a hole (about 0.2m in diameter and 0.5m above the floor)) in a vertically standing board</li>
<li>hit a hole (same hole) in a board lying flat about 0.5m above the floor</li>
</ol>
<br />
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.<br />
<br />
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.<br />
<br />
<br /></div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-85812291465013260642014-04-10T16:25:00.002-05:002014-04-10T16:25:45.889-05:00Oscillations of coupled masses<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="http://okphysics.com/4-15-oscillations-of-coupled-masses/">This is relevant to your interests</a>.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-41243445674756390162014-04-07T00:53:00.004-05:002014-04-07T00:53:51.864-05:00HW6 is out<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="http://faculty.mint.ua.edu/~pleclair/ph125/Homework/HW6_11Apr14.pdf">Here is HW6</a>, 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.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-5093975851786293352014-04-07T00:51:00.003-05:002014-04-07T00:51:52.924-05:00Solutions to exam 3 and HW5<div dir="ltr" style="text-align: left;" trbidi="on">
Here are solutions to <a href="http://faculty.mint.ua.edu/~pleclair/ph125/Exams/ph125_s14_exam3-SOLN.pdf">Exam 3</a> and <a href="http://faculty.mint.ua.edu/~pleclair/ph125/Homework/HW5_21Mar14-SOLN.pdf">HW5</a>. 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. </div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-51886741859465659962014-03-16T14:55:00.003-05:002014-03-16T14:55:27.748-05:00Formula sheet for exam 3<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="http://faculty.mint.ua.edu/~pleclair/ph125/Exams/formulas-ex3.pdf">Here</a> is a draft formula sheet for exam 3. </div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-72538576427937525512014-03-15T12:38:00.003-05:002014-03-16T18:24:06.808-05:00HW5<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="http://faculty.mint.ua.edu/~pleclair/ph125/Homework/HW5_21Mar14.pdf">Homework 5 is now ready</a>. 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.<br />
<br />
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.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-21524613023572674302014-03-14T01:00:00.001-05:002014-03-14T02:33:33.637-05:00HW4 solutions<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="http://faculty.mint.ua.edu/~pleclair/ph125/Homework/HW4_7Mar14-SOLN.pdf">HW4 solutions are available</a>. 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.<br />
<br />
<strike>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.</strike><br />
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?<br />
<br />
In any case, your HW4 solutions are ready. </div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-72393740873142978552014-03-13T01:45:00.002-05:002014-03-13T01:45:37.792-05:00The flow of wet and dry water<div dir="ltr" style="text-align: left;" trbidi="on">
Friday we'll finish up our discussion of fluids. So far we've figured out quite a bit:<br />
<br />
<ol style="text-align: left;">
<li>hydraulics (Pascal)</li>
<li>energy conservation in fluids without viscosity (Bernoulli)</li>
<li>variation of pressure with depth for an ideal fluid</li>
<li>work and forces to move fluids</li>
</ol>
<br />
<br />
We have a few things to sort out though.<br />
<br />
<ul style="text-align: left;">
<li>manometers: how to measure pressure? (simple application of 3 above)</li>
<li>how do gasses differ? (density variations can't be neglected; 3 + ideal gas law)</li>
<li>what about purely rotating fluids or smoothly flowing fluids? (energy balance)</li>
<li>what about buoyancy? why does some stuff float? (3 & 4 for a foreign object in the fluid)</li>
<li>what about drag forces/viscosity and terminal velocity? (subtle ...)</li>
<li>what can we say about pressure vessels? (simple generalization of force & pressure)</li>
</ul>
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.<br />
<br />
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): <a href="http://www.feynmanlectures.caltech.edu/II_40.html">Vol 2 Ch. 40</a> and <a href="http://www.feynmanlectures.caltech.edu/II_41.html">Vol 2 Ch. 41</a>. 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 <i>really</i> 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.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-83038879057364676582014-03-12T00:04:00.001-05:002014-03-12T00:16:01.975-05:00Rocket launcher deliverable #2<div dir="ltr" style="text-align: left;" trbidi="on">
<div class="tr_bq">
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.</div>
<br />
This week, I want you to tell me the following:<br />
<ul style="text-align: left;">
<li>Did you find that you need to use the same rocket and turret for reliable results, or did it not matter too much?</li>
<li>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? </li>
<li>Given the variability you find, approximately what size target do you think you could hit reliably? Ballpark answer is fine.</li>
<li>How does the actual range of the rocket compare to what you would predict without drag forces, evaluated for at least 2 angles?</li>
<li>How much kinetic energy must be lost to drag forces for each of those angles (say, a % of the launch energy)?</li>
<li>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?</li>
</ul>
<br />
<br />
<a name='more'></a><br />
I will give you at least 45 minutes, maybe an hour, on Wednesday to finish taking what data you need and think about these issues. If you want to do some additional work, you can take the launcher home with you until Friday to perform further tests if you let me know by the end of class that you wish to do so.<br />
<br />
You might find that the drag coefficient is different for small and large angles, it is possible (the rocket might tumble at high angles, for instance). What you're after is the best prediction of your rocket's motion, by any means necessary.<br />
<br />
<a href="http://faculty.mint.ua.edu/~pleclair/ph125/python/drag_force/simpler-drag.py">Here's a basic python program to calculate the trajectory</a>, assuming the acceleration due to drag is -Dv^2. If you want to account for the initial height of the rocket, you'll have to change ytemp=0 to be the starting rocket height.<br />
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Finally, <a href="http://faculty.mint.ua.edu/~pleclair/ph125/python/Rocket1.1/">Mr. Hampton has figured out how to control the rocket launcher directly from python</a>. This has a number of advantages over the provided program, not the least of which being that you can figure out how to directly set the angle you want. There are a few things to worry about, such as how to know what angle you're at to start with (hint: start from the bottom, it is always the same) and how far you've moved from there (hint: you control how long the motor moves, so you can calibrate this). If you are careful, you can control the start position and <a href="http://en.wikipedia.org/wiki/Backlash_(engineering)">backlash</a> in the gears to set the angle with pretty decent accuracy.<br />
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If you're interested in trying to control the launcher, let me know and I can give some suggestions for how to proceed. And many thanks to Mr. Hampton for figuring this out. This probably isn't something you'll find doable if you are totally new to programming. In that case you're not at a huge disadvantage, though, I can give you some hints on how to achieve similar accuracy without any code ...</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-87947197968971806102014-03-06T01:37:00.000-06:002014-03-06T01:37:34.349-06:00HW 4, revised due date<div dir="ltr" style="text-align: left;" trbidi="on">
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.<br />
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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.<br />
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Also, as it turns out, <a href="http://xkcd.com/">XKCD</a> has pointed you toward <a href="https://what-if.xkcd.com/85/">one of the solutions</a> already. The <a href="http://en.wikipedia.org/wiki/Randall_Munroe">author has a degree in physics</a>, 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.)</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-17081247488021420362014-02-28T11:54:00.005-06:002014-02-28T11:54:27.910-06:00Online coding<div dir="ltr" style="text-align: left;" trbidi="on">
If you're not so happy with Python, and would rather use another language for calculating your rocket's motion, I've found <a href="http://compileonline.com/">a site with a much larger set of available languages</a> 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.</div>
pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-1730745469008729850.post-54444318571266099862014-02-28T11:43:00.004-06:002014-02-28T11:43:47.599-06:00Rocket launchers, first deliverables<div dir="ltr" style="text-align: left;" trbidi="on">
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 <i>tell us</i> 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.<div>
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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.<br /><div>
<br />Your deliverables will take the form of a short memo (2 pages <b>maximum</b>), 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:</div>
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<ul style="text-align: left;">
<li>What is the launch velocity, with an estimate of its uncertainty. Does it depend on which rocket and which turret you use?</li>
<li>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.</li>
<li>What are the <a href="http://en.wikipedia.org/wiki/Drag_(physics)">appropriate equations of motion</a> 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.) </li>
<li>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?</li>
<li>What quantities can be determined experimentally ahead of time, and which will only be known once you know the target coordinates?</li>
<li>What are your potential sources of uncertainty, and how could you characterize them? A detailed plan is not necessary, just an idea.</li>
</ul>
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.</div>
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pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0