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Physics Extra Practice/Quiz Tickets
![]() For the 9th graders I'm now teaching, I wanted them to have some more tangible extra practice before taking an extra quiz in my standards-based grading system. My older students were a bit better at self-identifying what work they needed to do to prepare for an extra quiz, but they often ended up using extra quizzes as practice -- something I wanted to quash. Therefore, I made a number of extra practice sets that students must complete as a "ticket" to be able to take an extra quiz. Students turn in their completed practice ticket once they are confident that they understand the ideas, and if I agree, I stamp the top of the quiz with my spherical cow, print out the extra quiz, and then return the practice to the student. I've provided numerical answers for quantitative problems to help them gauge their work, but if there are still glaring errors in process, or I'm concerned that a student doesn't fully understand the idea, I indicate that at the top of the ticket. The student reworks the problems or comes to see me for help as needed. Click on the image below to take you to the extra practice/quiz tickets I've created and the directions I give my students for using them. The system made sense to my students, and they used the practice very effectively. Some of my overachievers used them to practice for our whole-class quizzes, and I'm certainly not going to stop anyone from doing some extra physics! A logistical note: I made all of the files in Microsoft Word and saved them in the Google Drive folder on my computer. Each time I make edits to a file, I also save it as a pdf. The links below are to the pdfs, and when update the pdfs, the links still work because the file name is unchanged and Google Drive automatically uploads the newly saved file. Click the image to take you to the extra practice tickets. I keep editing them, so you'll get my best version if you download them as you (or your students) need them. I hope you find them useful and/or inspiring! |
Spaghetti Bridge Lab
I love starting the year by asking my new class of students to show me what they can do: take data so that you can predict the number of masses that could be supported by a bridge made of strands of pasta. I used to provide a lot of guidance so that the students would get "good" data, but I've found that the less guidance I give, the greater the variety of student approaches (both good and bad) and the richer the post-lab discussion. After all, this lab isn't about developing a critical physical principle, it's about experimental design, communication, and setting a community norm that "answers" are based on patterns in data taken in a justifiable manner -- not on what the teacher says. This activity provides a great environment for discussing independent, dependent and control of variables. Depending on the level of your students, some might graph their data and write an equation for the graph, and the spaghetti bridge lab is a nice situation to use because the slope and y-intercept have accessible physical meanings. Materials: Uncooked long-strand spaghetti, thick and thin Large plastic cups or small cans. String to make a handle on the cup/can to attach to the bridge Unit masses: Marbles, washers, hex nuts, or pennies. I found some decorative squashed glass marbles -- they don't roll far when they hit the floor. [] Depending on your comfort level, don't be afraid to let the students come up with their own procedures. The important thing is for every group to explain their procedure in the post lab discussion. During this discussion ideas will emerge about how best to collect, display, and interpret the data. [] Let the students make mistakes -- but remind them to keep notes on how they collect their data. [] If you use marbles, have each group assign a "catcher" for the cup, otherwise there will be potentially dangerous marbles scattered all over the floor. ![]() Ask the students show their procedure and represent the pattern they found on large whiteboards. Choose one of the groups with a weaker board to go first. Ask the rest of the class to identify well-done elements on each board and to explain why those elements their communicate procedure and results well. As you make it to stronger boards, also ask the class for suggestions for making the data collection and presentation of data even stronger. You might assign a student to record items that the class feels are important to conducting a good experiment and presenting data clearly. Example whiteboards: Example questions: Experimental procedure questions: What was your procedure? Is the procedure clearly shown on the whiteboard? What was your independent variable? What was your dependent variable? What is meant by control of variables? How did you control variables? Why did you control variables? How is a dependent variable different from an in dependent variable? How did you know you had collected enough data? What is the advantage of doing multiple trials? Questions about the presentation of results: What are the features of a good data table? How did you convey the pattern you found? Use your pattern to determine the number of masses that could be supported by 10 (for example) strands of pasta. The whiteboard is a visual aid. What representations are most helpful in conveying what you did and what you found? Questions about the graphical analysis of data: (see the graphical analysis discussion below) What kind of graph best represents your data? Explain why you graphed this variable on the vertical axis and that variable on the horizontal axis. What does the straight-line graph tell you about the bridge? What does the y-intercept mean in terms of your bridge? How do you determine the units of the slope? What does the slope of your graph tell you about your bridge? Why do different groups have different values for their slopes? What variables affect the size of the slope? Under what conditions might you get a larger slope? What parts of the equation should have units and what parts of the equation do not have units? Graphical Analysis: Students graphing their data will find it to be pretty linear. draw a best-fit line, and determine the slope and y-intercept of their line. Students should be asked to write an equation for their graph. You may need to remind them of the general form of the equation for a line, y = mx + b. Example equation for load measured in marbles and strength measured in strands: (load) = 8 marbles/strand * (strength) - 5 marbles The slope tells how many marbles are supported by each strand of pasta. If the students use the word “per” or “over” be sure to ask them explain what the slope means without using per and over. For example, students should be able to explain that 8 marbles/strand means each additional pasta strand can support 8 additional marbles. The negative y-intercept is interesting and tricky. Students may notice that heavier marble cups result in larger, more negative y-intercepts. Lead students to observing that the strands never supported quite as many marbles as the slope would predict. Asked what else is putting a load on the bridge, students recognize that the weighted cups put a load on the bridge about the same size as their y-intercept. Therefore, the equation can be interpreted to mean that several strands of strength may be needed to support the cup before any marbles can be added. An equally fruitful discussion arises from describing the meaning of the x-intercept. An essential conclusion for students to reach about the graph is that the constants in the graph: slope and y-intercept, have physical interpretations related to the physical experimental setup. |
3D-Print Your Own Lab Clamps
Clamps! You can never have too many, and a great table clamp is indispensable when setting up labs in the physics classroom. But table clamps sell for $50-$100 each, so I set out to design a 3D-printable table clamp that was robust, multifunction, and low cost. Along the way, I designed a variety of other clamps as well that I've shared below. You don't have to print out many clamps before you've earned back your investment in a 3D printer. A disclaimer right up front: 3D printed plastic clamps will never be as strong and durable as metal clamps. Although I haven't had any of my 3D-printed clamps fail, I haven't let my students go wild with them, either. For most introductory physics lab activities, these clamps are stable, solid, and strong enough to get the job done, as long as you tighten the bolts with attentiveness to the strain you are putting on the plastic. If a clamp fails and your lab apparatus falls down, don't blame me! If you have a 3D-printer, great! If you don't, here's how you get a 3D printer: You: Dear person who holds the purse strings, I need 16 table clamps. Money Person: How much? You: $1600. Money Person: Seriously? No. You: Okay, here's an alternative: I need a 3D printer that I can use to print all the clamps I could ever need while providing my students with the opportunity to learn how 3D printing works and enable them to print their own designs. Money Person: How much? You: $1600. Money Person: Sold! I printed all of these clamps on a Lulzbot Mini 3D printer. At $1250, it is more expensive than many printers on the market, but it works so well. Cheaper printers will get the job done, but they often take more of your time to get them and keep them properly adjusted to work reliably while risking more failed prints. The Lulzbot has a heated platform, it self-levels, and its 8x8x8" print volume is plenty big for all of these lab clamps. ![]() I printed everything using PLA filament. ABS plastic would be stronger, but we don't have great ventilation in our 3D printer room, so we've put the ABS on the shelf until we upgrade our ventilation. I experimented with a variety of print settings and I settled on printing layers .25 mm thick, with walls 1 mm thick and a fill of 30%. This gave me good balance between strength and print speed. I have not yet experimented with annealing the 3D prints, which should make them up to 30% stronger according to what I've read. Annealing involves reheating the prints in an oven above the glass temperature of the plastic, but below the melting temperature of the plastic. This allows the internal stresses in the print to release while strengthening the bonds between print layers. ![]() |
Low-Cost Wave Generator Apparatus
There's something magical about standing waves, resonance, and the tangibility of the nodes and antinodes. Students love working with the waveforms, and they love the direct connection to the musical instruments they play, how harmonics work, and the physical principles behind them. Unfortunately, most science suppliers sell a wave driver apparatus in three parts: 1) the thing that does the shaking, 2) an amplifier, and 3) a function generator. Depending on the supplier, one full setup costs between $500 and $1000. That's a bit steep for me, so here's a homemade version that costs about $30 in parts and takes advantage of the capabilities of your smartphone. I'm leading a make-and-take workshop to build these for your classroom on March 5th, 2017, from 10 am - 1pm. If you are available to join me at Teacher's College, Columbia University, I'd love to see you there. Registration for the workshop is $20, and wave drivers are $30 each. You can sign up for the workshop here: https://www.eventbrite.com/e/wave-generator-makentake-registration-30285815690 In the workshop we will run the labs you can do with this equipment as well as build the apparatus. Design Features: The apparatus consists of a 4-inch speaker, a 50 Watt mono amplifier circuit, a 12-volt power supply, and some laser cut acrylic pieces that tie things together. All parts are mounted to a central acrylic plate that includes notches for cable management when not in use. You need to supply a ring stand with a flat metal base. The metal rod acts as one anchor for the string and the acrylic pyramid mounted to the speaker cone shakes the string. The magnet in the base of the speaker sticks nicely to the metal base, and a hole in the acrylic plate locks it onto the ring stand rod. This makes the overall apparatus much heavier so that it doesn't go wandering all over the lab table. There are a variety of smartphone apps that feature tone generators or frequency generators for free. I've been using one called "Function Generator" on an iPhone which works fine, though it's filled with pop-up ads. You want a program that allows you to increase or decrease the frequency by tapping add 1 Hz or add 10 Hz. Interfaces dependent on a slider or having to type in the frequency are difficult to use for this application. I want to give a shout out to the Physics Toolbox app that gives you access to all of the sensors in your phone. (Check it out!) The Physics Toolbox has a tone generator for Android that allows you to change frequency by tapping, but it does not work that way on iOS. There isn't anything that complicated here that you couldn't do with a saw and a drill, but once I refine my prototype for the workshop, I'll post the cutting templates and a detailed parts list here to save you some time. I'll also share the curriculum materials that go with the lab and the followup analysis. |
Soda Can Photoelectric Effect Demo
I'll also tout the soda can electroscope, which, for the low-low cost of dumpster diving, is superior to commercial electroscopes as far as I'm concerned. The pie-plate electrophorus is also as good or better than any commercial one on the market. Just imagine what Ben Franklin might have discovered with access to the wonders of modern take-out containers. As it was, he had to do with pewter and wax -- it was definitely a different time. |
LED Photoelectric Effect Apparatus
I first encountered Wayne Garver's low-cost LED photoelectric effect apparatus at a St. Louis Area Physics Teachers workshop in 2005. Since then, I've been involved with building dozens of these. This latest version has some simplifications and additions that make it even more useful. Wayne's insight is that the essence of the commercial apparatus is the vintage phototube at the heart of the device. All the other parts are pretty simple and inexpensive. So for about $100 in materials, you can build an apparatus that will do everything that the $500 version in the science catalog will do. ![]() In the fall of 2015, my engineering classes built 30 photoelectric effect devices as an orientation to using tools and soldering. Some of the solder joints aren't pretty, but they all have been tested and work fine. It was a great mix of practical skill development and service to the school and the science teaching community. At the upcoming workshop, we're selling the apparatus for the cost of the parts.
In April 2016 I am offering a workshop on the photoelectric effect and how to get the best learning impact from the device. If it isn't yet April 9th, sign up to join us! https://www.eventbrite.com/e/photoelectric-effect-make-n-take-workshop-tickets-22946066302
The light source for the device is a set of LED's. Since all of the LED's are clear, it is necessary to label them. I was ready to pull out my model railroad paint when one of my workshop participants in 2014 suggested using fingernail polish. What a brilliant solution! Here's a close up. Here are the directions I've written up for constructing the apparatus. Click the image to open the pdf. |
Slow Acceleration Apparatus
So that students develop a real kinesthetic sense of accelerated motion, it is ideal for them to investigate the acceleration of an object that speeds up so gradually that the motion can be tracked by hand. Rex Rice, of Clayton HS in St. Louis, developed an elegant solution using a wood disk with an axle made from two golf tees. The wheel and axle rolls down two conduit pipes, and students can mark the position of the axle at equal time intervals, getting 20 to 30 measurements depending on the incline. After making hundreds of these -- it's no small task cutting 4" disks out of MDF and drilling centering holes in the end of the golf tees so that they align appropriately -- Chris Doscher suggested to me that we could use CD's for the disks by using a faucet washer to attach them to a metal axle. The metal axles are less ideal because they don't have the self-centering feature of the tapered golf tees and the friction between the steel axle and the steel pipes is low enough that they have a tendency to slide on the pipes. One fix we have added is to run a strip of masking tape down each pipe to give a bit better tooth. However, we sometimes found that the disk's acceleration decreased as the wheel approached a terminal velocity with the tape -- be sure to test it ahead of time! I haven't tried it yet, but I want to spray the axle with a clear lacquer to change the friction characteristics. The teacher's notes for the Uniformly Accelerated Particle Model on the AMTA site spell out the details, but here is an outline of how you could use this apparatus in an instructional sequence: 1. Introduce the activity in terms of prior explorations in constant velocity. Our goal is to quantitatively describe the motion of an object that has a changing velocity. Students will recognize that they can use the same data collection procedure that they used in the constant velocity lab. 2. Students collect data for the moving disk. 3. Students make a position-time graph. Since it's curved, guide them to the idea of finding velocities at different times of the motion by drawing tangents to the curve and finding the slope. 4. Students make a velocity-time graph. In the discussion, acceleration is quantitatively defined. 5. Students are challenged to make and analyze additional graphs: "Linearize" the position-time graph by making and analyzing a position-time squared graph. Graph velocity vs. position and linearize the graph. By the time the analysis is done, all of the accelerated motion equations have been developed from the data. |
Mega Can-Crush
I've done the can crush lab with my students for years, but only crushing soda cans. I find this image of a crushed railroad tank car fascinating and I wrote a quiz based on it for use in Modeling Chemistry Unit 3. By the way -- the steel that makes up the tank on a DOT-111 tank car is 7/16" thick and has a capacity of 34,500 gallons. Because the DOT-111 design has been involved in several recent oil train accidents, the DOT-117 design will replace it, with 9/16" thick tank steel and full end shields. Interestingly, when MythBusters tried to crush a tank car with air pressure, they had to apply some extra assistance in the form of dents to weaken the structure. As a railfan, I follow all kinds of information about trains, and I also came across this on Trains.com news feed: From trains.com on July 7, 2015: Kelso Technologies Inc. obtained approval from the Association of American Railroads to begin commercial field trial testing on the company’s new Vacuum Relief Valve. The low-pressure device is specifically designed to protect tank cars from the effect of an excessive vacuum, preventing the implosion of the tank car. The patent-pending valve design is a result of customer demand for a better performing product due to the failure rate of products currently in use. The device meets the new DOT-117 tank car specifications to be implemented later this year. Kelso is a railway equipment supplier that designs, produces and sells proprietary tank car service equipment. For more information, go to www.kelsotech.com. |
Upgrading an old website
Dear friends, I started this website over 15 years ago as a resource for my students and, as it turns out, for the wider Modeling community. I've also thought a lot about developing storylines that connect the entire science sequences together by considering what is central to the scientific subdisciplines and what will set students up for subsequent studies and science. When considered in a holistic way, the physics first sequence makes perfect sense and Modeling approaches in physics makes it doable.I have had the opportunity to teach physics in grades 9-12 in public and private schools, and implementing the Modeling Instruction philosophy with each combination of variables required customized curricular approaches to best fit my students. I'm now at a school that has its own password-protected web system and maintaining multiple web platforms has been too much to keep up with. Therefore, some upgrades are needed. This site is now designed specifically for teachers. My students can get what they need through my school site. This tighter focus will make the site easier to use. Most of the physics materials I've created and the resources I've assembled are available through the American Modeling Teachers Association website. They have a great platform for exchange of ideas that compiles the resources and brains of hundreds of teachers throughout the Modeling Instruction community. Many bloggers have done an excellent job of addressing questions and providing excellent resources for teachers. I will add to the blogosphere when I have something to say, but I will also happily refer you to the excellent thinkers out there who have stated things beautifully. My own writing has also appeared on the AMTA site and on the STEMteachersNYC site. I've branched out beyond physics. I've now taught Modeling chemistry, environmental science, astronomy and modern physics, and engineering. I also have a dozen years of experience with middle school astronomy and meteorology teaching. Along the way I've learned a lot and have generated some resources that may be worth sharing. |
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