The Next Generation Science Standards place a new importance on engineering. There will be initiatives and ideas for how to engage students in designing and building things in class.
If we want to enmesh engineering into the fabric of our curriculum, we might want to consider shining a spotlight on the engineering history a few key inventions. The PBS series, Breakthrough: The Ideas the Changed the World shines that light on six such triumphs of engineering. The series played on PBS this past spring It streams on Amazon Prime. And the DVD set of the series, hosted by Patrick Stewart, is now available. Here's a rundown of the episodes.
The Telescope
Episode 1 tells the story of the development of the telescope, from a stone-age observatory to the space-based telescopes of the future.
It entails long-abandoned Stone Age dolmens once used as celestial calendars,
how Venetians made glass transparent, the optics of a medieval Persian camera obscura, a Dutch lens maker’s wartime breakthrough and a Venetian math teacher’s advancement of it, a Parisian invention improved by a spilled bottle of mercury, a team of women known as human computers who were armed with fly spankers, an athlete-turned-astronomer working high above Los Angeles, and telescope in space that will allow us to see as far as physics will allow.
Episode 1 "breakthrough celebrities" include Galileo Galilei, Edwin Hubble, Henrietta Swan Leavitt, Louis Daguerre, Hans Lippershey, and Ibn al-Haytham.
The Airplane
Episode 2 tells the story of the development of the airplane, from early human-powered attempts to the jet concepts of the future.
It involves a ninth-century moorish daredevil’s first attempt at human flight, how we had tails before we had wings, an artist obsessed with anatomy and flight, a whirling arm in the stairwell of a seaside mansion, the rubber band’s role in flight, the curve of a stork's wing, a connection to maritime technology and the gyroscope, the use of a deep-sea diving suit to fly high, why modern pilots are pressure tested, and the surprising efficiency of the jet propulsion gas turbine.
Episode 2 "breakthrough celebrities" include Leonardo da Vinci, Wilbur Wright, Orville Wright, George Cayley, James Doolittle, Wiley Post, Frank Whittle, Elmer Sperry, Lawrence Sperry, Otto Lilienthal, Alphonse Penaud, and Ibn Firnas.
The Robot
In episode 3, Locutus of Borg tells the story of the development of the robot. Well, Patrick Stewart is the series narrator, so... close enough!
It involves the ancient legend of Hephaestus and rudimentary Greek automatons,
a device that could learn a new tune and repeat it exactly, a desire to produce navigation tables by steam, the linguistic contribution of a Slavic cubist painter, the breakthrough of storage for programs, an imitation game, an electronic tortoise, a mission to Mars, a nuclear disaster in Japan, and the challenges of balance and hands.
Episode 3 "breakthrough celebrities" include Alan Turing, Charles Babbage, Ada Lovelace, Hero of Alexandria, William Grey Walter, The Banû Mûsâ brothers.
The Car
Episode 4 tells the story of the development of the car, from ancient sleds powered by primitive dogs to autonomous vehicles powered by graphene batteries. Gary Numan was not available for the narration, so Patrick Stewart handled the voice-over.
It involves ancient arctic sled dogs, the pairing the axle to the wheel, the smelting of metals from rocks, the spreading of a language, the need to pump water out of mines, the boring of naval canons, a stunt carried out by an inventor’s wife, the efficiencies of a slaughterhouse, and the promise of graphene.
Episode 4 "breakthrough celebrities" include Henry Ford, Karl Benz, Bertha Benz, James Watt, Thomas Edison, John Wilkinson, Thomas Newcomen, and Jay Leno.
The Rocket
Episode 5 tells the story of the development of the rocket, from ancient guano-powered fireworks to plasma rockets with magnetic confinement.
It involves the use of bat guano from Chinese caves to drive off evil spirits, a modern-day celebratory rocket battle in Greece, a work of fiction by a famous astronomer, an imaginative tale about a trip to the moon, a visionary living in rural Russia, a breakthrough in dairy processing technology, a loophole in an international treaty, a repurposing of firefighting equipment, internal Soviet geopolitical subterfuge that stoked the Space Race, and plasma engines that could transport humanity to other worlds.
Episode 5 "breakthrough celebrities" include Robert Goddard, Werner Von Braun,
Konstantin Tsiolkovsky, Jules Verne, Ti Tian, Sergei Korolov, Karl Gustav, Thomas Harriot, and Johannes Kepler.
The Smartphone
Episode 6 tells the story of the development of the smartphone, from the fall of Carthage to brain-interfaced apps of the future.
It involves ancient Roman battlefield communications, a painter-turned-inventor who devised a code still in use today, a groundbreaking technology whose rightful inventor had to be settled by the US Supreme Court, an obsessive inventor who found treasure in another scientist’s trash, a quirky keyboard talking machine, a Hollywood starlet who was also a prolific inventor keen to defeat the Nazis, the miniaturization of a circuit invented by an engineer who hadn’t yet earned vacation time, and a father eager to share a photograph of his newborn daughter with friends and family.
Episode 6 "breakthrough celebrities" include Alexander Graham Bell, Samuel Morse, Guglielmo Marconi, Hedy LaMarr, George Antheil, Jack Kilby, Polybius, Philippe Kahn, Homer Dudley, and Elisha Gray.
In the event you've severed all your social media ties, you might have missed this week's viral video. So allow me to present Mark Rober's "magnum opus" as a public service.
The notion of delivering a modicum of justice to porch pirates strikes a chord in most of us. I'm confident that simpler solutions cannot be far away. With luck, this project will soon be an amusing tale of "back in the olden days".
Some viewers were skeptical of some of the reactions. Rober confessed to being too aggressive in seeking glitter bomb reaction footage and pulled a few of the clips after determining they were not genuine. I saw one YouTube "skeptic" who seemed a few marbles short of a full deck ranting that the whole enterprise was paid for by Amazon. This guy seemed to be hoping that making a vile video would generate viral video revenue. And no, I'm not going to link to it here.
Of course, one takes some risk slapping back at porch pirates. They cast themselves as sociopaths by their criminal conduct to begin with. And having their poor judgment highlighted to them may not set them on the right path.
Still though, a nice story of using STEM skills to deal with a common, real-world problem. STEM coursework isn't the easiest, but mastery of some of it can make you powerful, indeed.
Throughout the year I mentally categorized everything as either pre- or post-AP. When I finally made it to the promised land of post-AP testing I then encountered a new challenge, keeping students engaged for a few weeks when they want to do absolutely nothing. I had many options, even putting a poll to them just for information (reserving the right to completely disregard their #1 choice of "do nothing"). I could talk about topics not covered in AP C like waves or optics or thermo or relativity? We could do a research project or have some kind of demo build? They could present a talk? Some ideas seemed better than others but the timing wouldn't work.
I finally settled on doing a series of group competitions, something different each day, something hands on and fun. I found lots of ideas online, some from labs I didn't get to do, but did struggle to find ones that were Electricity & Magnetism (second semester) focused instead of Mechanics (first semester) focused. I was hoping that the competitions could be on the same topics they would later be tested on for their end-of-semester final. Unlike most AP classes, I opted not to give students a final prior to the AP test. The argument is usually that students need the practice of an AP-like exam prior to the test; so we completed mock AP exams for practice but not for a grade. My students may take up to six AP classes in their junior or senior year so they have several weeks of high stakes testing (class finals) before more high stakes testing (AP exams). I decided that the practice and their mental health was more important than their grades at that point in time and they could take the final exam during finals week.
Since I was building the competition up from scratch there was a lot of writing, re-writing, last minute tweaking and of course post notes for next time. In the end it was a workable model with no major issues but as is often the case with the first time through, it wasn't quite right. In either case now I have examples and procedures for a series of activities to either use in the same way next year or throughout the year.
Day 1: Explanation and Bridge Building
On the first day I explained to them that they would be arranged into groups and competing each day for the rest of the school year. Each group was assigned a Greek letter and asked to come up with a clever name using the letter. I tried to split Chi, Psi, Pi, etc. from being in the same class and removed Alpha to save as my example of "The Alpha Academics." As expected, my students were way more clever than I and came up with some great names: Gamma's Cookies Oof (Omicron upper and lower case) Beta Testers Mooupsilon Kappa-citor An Iota of Understanding
I introduced the format of the competition using this powerpoint. It had the rules, grading specifics and the explanation for each day's competition, which was never revealed ahead of time. I explained to students that coming up with the name for our little competition was hard, I almost decided on the Phunger Games (like the Hunger Games series) but just couldn't. It came down to the morning of when brilliance struck and I decided to name it the PhysX-Games, complete with logo based on the popular X-Games:
Students were of course very concerned about how their grades would be affected by the competition. I did not wanted to punish them if their group didn't win every day but I wanted everyone to put effort in. I also wanted them to be rewarded for working well as a team and accomplishing tasks. I opted for a system that separated individual effort from group effort. Each day that students were present they could earn 5 points for actively participating. Each group would earn points for the day for accomplishing the task but they would earn more points for being the best at it. Good participation on an individual level required helping their group for the whole period. Sleeping, doing other homework or being caught with a cell phone meant zero points for the day. These participation points went into students' lab category so it was a welcome bump for most. If a student was caught with a cell phone that day their group could not win the competition, but it did not negatively affect the other group members' individual points. I would keep a running tally of each group throughout the competition so we could always see who was in the lead.
But why care if you are "winning"? The prize had been another sticking point initially. What do I offer students who are only a few weeks from graduating, that are mentally "done" after AP testing? I hadn't offered extra credit all year so it seemed like a good reward. Specifically I decided to add enough extra credit to their individual final exam grade so as to boost their semester grade by 1%. Yet with three classes of AP Physics C I had to find a way to limit my first few periods from giving the last class the "answer" to the challenges each day. I needed a way to keep groups between classes competitive. So I upped the reward. The group with the most points in each class would get points added to their final exam to raise their grade 1% but the group with the most points across all three classes would get 2% added to their grade. This was met with hoots and hollers in my classes. I need not worry about answers being shared between classes, they were in it for a grade bump and the competition was fierce.
After the explanation and group naming we didn't have time for a long competition on the first day. Instead we started with something basic, balancing uniform sticks over a table edge. Groups were given five uniform paint stirrers and five uniform meter sticks. They were given instructions which included the rubric I would be grading them on. Without attaching the sticks in anyway to the table or counter-weighting them students were to extend each group of five out as far past the table edge as possible. Points were awarded for balancing the sticks and a bonus was given to the group with the farthest reach for paint sticks and another for the farthest reach for meter sticks. I did find that my naming it a Cantilever bridge was a bit of a misnomer; the activity is similar to the Take It From The Top activity from the Exploratorium.
Initially students tried to use some of the meter sticks as their own counterweight so we had to specify that the farthest extended meter stick had to be the top one. Students were to calculate the hypothetical Center of Mass of the system based on their measurements and assume no thickness to the sticks. The record for paint sticks was 41.4 cm and the record for meter sticks was 120 cm off the table. Groups would go back and forth, adding millimeters at a time as the record was erased and rewritten on my front board. It was a tense day in Physics!
Day 2:Mass & Spring
To review oscillations and simple harmonic motion (SHM) I adopted a lab practical challenge I had read about but unfortunately can't remember where. Students were challenged to hang the correct mass from a spring so that it's period was as close to 1 second as possible. Again their instructions included the rubric so they knew how to earn points. Students are given no other information however, and have to first determine what they need to know about the spring in order to find the needed mass. Once calculated, students would hang the mass and spring from a Vernier Dual Range Force Sensor and start it oscillating. They would use the software to determine the period for five cycles then divide by 5 to find the period for one cycle. Each class was assigned a different target, 0.5 s or 1 s or 1.5 s. I had used stiff, old springs that students had not worked with before so that they had unknown larger spring constants. This meant that the 1.5 s period required a large mass and so I changed it to 0.75 s for that class. Students used the Vernier probes to calculate the spring constant as well and so everyone got very accurate results as seen at below.
The second stage of the competition was to determine the mass of an unlabeled or hidden mass using the same procedure but in reverse. I used several old masses found in the back of my cabinet that had had their labels worn away over the years. I also made unknown masses out of toilet paper tubes and dead batteries. Each mass was measured and recorded so that I could see how close each group came. If they calculated the unknown mass to be within 10% of the actual they received group points. The group closest to the actual mass received bonus points; bonus points were also awarded for the group that got closest to the assigned period.
In the future I think I will decrease their accuracy by only providing a spring scale for the initial determination of the spring constant. This will make it harder for groups to get so close to the assigned period and award groups that employ careful lab techniques. I would still use the Vernier probe to determine the period of the oscillating mass.
Day 3: Flying Cups
Since our competition started during the second week of AP testing there were still students that were occasionally gone to take AP Exams. On those days they did not earn their individual points for participating in the PhysX games but they were also not penalized for missing them, it was excused. If they were *cough cough* "sick" that day however, they would have to complete a make-up activity. If the equipment could be easily gotten at home they could do it there but some competitions required sample data for their alternates because students did not have the equipment at home.
The Flying Cups competition however, could easily be done at home. I saw this for the first time at an elementary school Science Night and immediately decided to do it in my classroom. This video (also below) explains the how to's and the teacher flies several different models. Essentially two identical cups (made of paper or thin plastic) are taped together at the bottom. A chain of four or more rubber bands is made and wrapped around the center of the cups and held on one end. When the cup is released and the rubber band chain pulled the cup is launched forward.
Each period, 30+ AP students were completely engrossed in flying these cups. They tried all kinds of models, trying to figure out if paper or plastic worked better, a longer rubber band chain or shorter, more rubber bands or fewer, added mass at the center or the edges, etc. In the end a few smart students realized that launching from on top of a picnic bench gave them a distance advantage. Soon everyone caught on and eventually the whole class launched from a small hill in the center of our school. Some students were better launchers than others, one of the more successful being a varsity baseball pitcher. Groups earned points for each meter their cup traveled before striking the ground (not rolling) and had a bonus for the farthest in each class. By the end of the day the record was 14.7 m, with most groups over 9 meters. It was a simple activity, definitely mechanics but very fun.
Day 4: Leyden Jar
This was an activity that I used to do for years in my regular Physics and even Conceptual Physics classes. I taught students about parallel plate capacitors by having them build a simple Leyden Jar out of a film canister. I still hoard film cans to this day even though I haven't had time in the curriculum to do this for years. For the competition students were instructed to use a small film can, or a jar if they brought their own, to make a simple capacitor. This old video of mine shows the basic construction:
I had asked students to bring in cups for the flying cups activity and jars for the Leyden Jar activity without telling them what it would be for (so they didn't research it in advance). A larger jar would increase the capacitance their jar could hold, something they realized too late. Students were challenged to build a Leyden Jar that would hold a charge and then asked to hypothetically calculate what the capacitance should be using the cylindrical parallel plate equation they found in their textbook. After their calculation we charged up their Leyden Jars with my Whimhurst machine and measured the capacitance using my new capacitance meters.
I found that you have to be careful to stop charging the jar before it discharges itself, something that happened quickly for sloppily made jars. I used alligator leads to connect the Whimhurst machine (with discharge electrodes far apart) to the inner and outer surface of the jar being tested. At least one of the leads had to be removed for testing or you would measure the capacitance between the much larger Leyden Jars of the Whimhurst machine.
Students got HUGE errors between their theoretical and measured capacitance, as in the hundreds ofpercent. I need to improve the testing system if I ever want points to be awarded based on their error. Students had to research the dielectric constant of their jar, be it plastic or glass, and there is a lot of variety in that value depending on the actual material. Also without a pair of calipers students had to try to estimate the thickness of their jars as best they could. One creative group asked to borrow box cutters to cut off the thicker lip around their film can so that they could more accurately determine the thickness. Generally the smaller film cans had a higher percent error and a smaller capacitance. The large jars brought from home tended to be more accurate and their larger surface area gave them a larger capacitance. My students were able to produce capacitors from 10 (film cans) to 100 (glass mason jars) picofarads.
While I liked the review of capacitance, specifically what it was and what physical attributes of the capacitor affects its capacitance, the build was pretty easy. There wasn't too much difference between the capacitance of a well made or sloppily-made jar from the same film can. One student made a simple flat capacitor about 4x6" just for fun and it had a capacitance several orders of magnitude larger. Another variation may be to assign a certain dielectric material, plastic or paper or cardboard, etc. and a certain capacitance. Students would have to determine the size of the parallel plate capacitor for that particular thickness of that particular dielectric to achieve that particular capacitance. I feel like it would be more accurate, easier to test and I could judge them based on their accuracy to their hypothetical.
Day 5: Mystery Circuit
This was a variation on my Electric Building (House) Project for regular Physics and Conceptual Physics. I gave each group a shoebox that had a lid with their instructions and made paperclips, brads, wire cutters, wire strippers and holiday lights available. Unlike the previous project students got to design whatever circuit they want as long as it met the conditions:
1. Uses only one 9 V battery.
2. Has at least 8 lights.
3. Has at least 2 switches.
4. All lights can be lit up, all lights have to be able to be turned off (for storage).
Groups were to design their circuits, build it so that just the lights were visible on the outside of the box (rest of wiring hidden on the inside) and make a matching circuit schematic. That earned them the minimum points for accomplishing the task. When they were done each group were to exchange their mystery circuit box with another group and try to guess the schematic. Each group that they successfully stumped earned their a bonus point. I told them that it was quite possible that each group would be stumped and earn points after the exchange.
We did have a few hiccups on this one that I was not anticipating. In my first class of the day we found one LED strand of lights that was masquerading as an incandescent one. Since LEDs are directional it was very difficult for students to build a working circuit with them. And since relative brightness of bulbs is usually how students guess how bulbs are connected the equally bright LEDs wouldn't work for this task. Some of these groups got pretty far into their build before the mistake was recognized and ratified. I had also expected that since students had built a simpler circuit in the same way last year in regular physics they would be able to build this more complicated one quickly. I was wrong. We ended up taking two days to complete this and some groups never did.
There were a few groups that made their circuits so complicated that even they weren't sure how it worked, or the load was too high and it never did. Hurried and/or loose connections made it difficult to judge if their circuits matched their diagrams. Some made simple light connections but used the switches to complicate it, which was more of what I was hoping for, like below:
In the future I think I will limit the number of lights, switches and perhaps more strongly emphasize that all lights must light (not that "Technically a microamp could be flowing through it even though it looks off"). I will have to give them more instructions on how to make the switches, strip wires, etc. I expected students remembered those skills from the previous year; which assumes they did actually build the project they turned in. In the end the activity worked but I wasn't really satisfied with the quality of the project or their efforts.
I had also hoped to keep this year's projects (hence the requirement that they had to be completely turned off) so that perhaps the next year I just asked groups to map the mystery circuits made this year. So few were working a week later when I went to dismantle them that I had to abandon this idea and instead scavenged them for parts. Side note: I take apart all but the very best Electric House projects each year to save the parts (brads, paperclips, bulbs, 9Vs, motors) for the next year.
Day 6:Defibrillator
I got this idea from Frank Nochese on Twitter about challenging students to build a defibrillator model like an RC circuit. I researched defibrillators and put a call into my sister who is a registered nurse to get the low down on how they were actually used and how that related to the circuits my AP students had used. Turns out that the typical movie scene is completely wrong (and a pet peeve of medical professionals everywhere). Usually a patient is shown flat lining (no more heart beat) and it is then that a defibrillator is applied and the doctor charges it up and shouts "Clear!" and a big thwump is heard as the person/ body jumps up on the table. This is repeated until a heart beat is restored. In reality the defibrillator can only be used when there is still a heart beat but it is irregular. A loss of a heart beat means that chest compressions must be applied in order to restart the heart and get it beating again.
When I researched how they actually worked I found that the first prototypes used AC current and modern ones used inductors. I didn't have any inductors so I opted to still use Frank's original plan using an RC (resistor-capacitor) circuit. Real defibrillators use inductors so that the current oscillates, the oscillation can be controlled to match the desired heart beat. An RC circuit model would simulate one "beat" if you will because it would only charge and discharge once. My research led to a few additional questions about defibrillators and the more physics related concepts that I've added to the bottom of the instructions page.
Groups were told that they could use whatever resistors and capacitors they wanted to meet the requirement to save their "patient." I made little paper hospital gowns to go around the "patient" resistor so that students wouldn't get confused when they had multiple resistors in the circuit. It needed a little paper cot as well. These just might turn into fabric ones by next year ...
Each class was assigned a specific "patient" resistance, the maximum current that could go through it and a maximum charge on the capacitor. Groups had to first figure out what their circuit might look like then use those maximum values to determine the specific size capacitor and total resistance to use. I had 100 or 2200 microfarad or 1 farad capacitors for groups to choose from. Almost everyone ended up using the 2200 microfarad. I had a shoebox, literally, of organized resistors for students to work through. They were not as organized when we were done. Some groups couldn't find exactly the value of total resistance they needed but found getting within a few ohms was fine. A few groups wanted to stick to only one resistor (or mistakenly thought that the "patient" resistor was the only one allowed in the circuit) and therefore tried to add a few capacitors in series or parallel.
Once students had built a circuit that allowed them to charge their capacitor (not through their patient) and discharge it through the patient they attached meters. We could probably have done it with multimeters as Frank did initially but I opted for our Vernier voltage and current probes since we had them. Since the currents were in the milliamp range the graphs are so small. Most groups got a good decay curve for the current through the "patient." I had wanted students to also measure the voltage across the capacitor and the resistor but often this was not done due to time.
Next time I won't have all my resistors out. I shudder to think of the order of the envelopes of resistors in that box when I go to look again. I would still have a variety but will try to pair down their options. I did not assign the additional context questions (below) that I wrote this time, they were my backup in case it didn't work at all. Next time I would definitely include them as I like them and think they bring some background to the activity. Other than that I think it was a great lab practical for RC circuits that Frank came up with and I will definitely use it in the future. This is one that I would like to add to my regular curriculum, if we have time.
Day 7: Trivia
This was the Tuesday after Memorial Day weekend, the last real class day before finals. I thought the last day of competition would be a good day to review the material for their final. Rather than using a Jeopardy type format, in which can be slow and often leads to one group keeping control of the game, I opted for a pub trivia format. If you aren't aware a lot of pubs or breweries have Trivia Nights that include teams that come back each week and multi-month tallies of points. Rather than having groups shout out answers or use a buzzer groups submit their answers to questions in writing. Everyone who gets the answer right can get the point, the question move along quickly and you can maintain a bit more decorum. I wrote up over 60 questions spanning the whole Electricity & Magnetism semester, some were multiple choice, some shorter response and some calculations. Each question had a timer for either one minute (conceptual) or two minutes (calculations & short responses) on the slide itself.
Before we began I went over the rules with each class:
•All
groups will be asked the same questions and record their answers on a sheet of
paper to be turned in and graded later.
•NO
CELL PHONES OR OTHER ELECTRONIC DEVICES, TEXTBOOKS OR NOTES ALLOWED. These are
questions to be answered by your brains alone.
•Do
not shout out answers. Do not talk to other groups. Whisper with your group.
•Groups
earn points for each right answer. The group with the most points will earn an
extra 5 points.
•Each
question has a time limit before the next one is shown but you can write
answers to previous questions if you have extra time on another question.
•You
can have more than one paper and pencil out but must turn in one answer sheet.
Groups used whiteboards for their work or discussion/ debate drawings but kept all their "final answers" on a separate piece of paper I would collect at the end. I was able to sit down and read each question as it came up, the counter ticked by and then moved the slide forward for the next one. Students kept on task and most groups attempted all questions. Sometimes there was a lull as they answered a question in less time than was given but sometimes they ran out of time. I encouraged them to record information for questions they ran out of time for so that they could go back on questions that they had extra time for. In the end I collected all the papers and graded them, awarding a point for each right answer. Since there was only one per group it did not take long and sometimes I offered partial credit. The group with the most questions correct also got the bonus points.
What was difficult was the mixing of the questions. We weren't going to get through all 60+ questions in each class so I tried to skip around so that they got a sampling from each major unit (electrostatics, current electricity, magnetism, etc.). This confused some of them as they had to number their answers with the question number which may not have been the number following the last one. There were some questions I wanted every class to get and I found myself having to record on a scratch piece of paper which classes got which question. I'm sure there is a program or website that would improve on this model and I'll have to look for it before next year.
In the end the competition did what I needed it to do: engage the students in some fun physics exploration until the end of the school year. I think my students enjoyed it, especially since they didn't have homework, but it could use some improvements. For one, I don't think it did as good of a job helping them to review for their final exam. Their final exam scores were lower than I would have like, especially since for many it was their only "real" final exam after earlier AP finals. I expected the activities to keep them thinking about the content, which to an extent they did, but it did not help with remembering the finer details and tougher problems they needed to review. Many thought they still knew the material well enough not to have to study, a problem unrelated to the competition.
The points for several groups in each class were quite close, the winners only being a point or half a point ahead of the rest. It was nice to see though that different groups won different competitions. A few groups won twice over the course of the competition (thus earning bonus points) but it was not necessary to be the winner in each class. I would want to tighten up the system of awarding points, try to find activities that require more content knowledge for this semester and increase the difficulty of some of the activities. It wasn't bad for a first run but I anticipate the PhysX-Games of 2019 will be much better.
Last fall I met with Venu Nadella, the founder and director of Janyaa. Her organization promotes hands-on learning for math and science in India. They provide support and inexpensive kits to schools across India at no cost. So far they have impacted 320,000 students in 930 schools in India and are piloting programs in other countries. You can make a donation here. Venu asked me if I would serve on their advisory board and help develop science activities and kits. The offer sounded interesting so I agreed.
My first assignment was to develop lessons for curved mirrors. Not being familiar with Indian curriculum standards, I sought out a textbook for guidance. I soon found that India posts all of their textbooks for free in many languages. You can find them all here. The one I needed was the 10th grade English version of Physical science, 10EM_P. At right is the index with suggested pacing. I needed to develop activities for chapter 3, Reflection of light by different surfaces. My initial thought was to find some inexpensive curved mirrors. One good choice was a 7.5 cm diameter mirror offered by Teacher Source that is coated on both sides so it is both concave and convex. Unfortunately, even its reasonable $7.95 price was probably too much. I remembered seeing a curved mirror at a NCNAAPT meeting show and tell session made with silver mylar. A rigid shallow cylinder is closed at one end and covered with mylar at the other. Air is pumped out, resulting in a nearly parabolic shape to the mylar. I decided to try my hand at making my own curved mirrors.
I did some searching online and found several DIY videos on making concave mirrors with silver space blankets. This one was helpful but too complex. When I found this one that uses a trash can lid, I realized this could work. The problem would be finding an easy way to change the pressure inside. While sipping a glass of wine at home I had an inspiration. I could mount a Vacuvin wine saver to the trash can lid and pump the air out. The stoppers are only about $1, one $8 pump can be used for multiple mirrors, and this is a LARGE concave mirror. I ordered some strapping tape, silver space blankets, and silicone sealant. I went to the hardware store for some trash can lids. It turns out they have a lot of extra ones because people replace dented metal cans but leave the lid behind. They gave me 2 lids. I followed the DIY video directions as close as possible. The only modification was a larger hole to accommodate the Vacuvin stopper. My first attempt had a few leaks but those were easily covered with more tape. I pumped out the air until I heard the lid start to deform and turned it around. I had a pretty good concave mirror with a focal length a little less than 1 meter. Above is my TA using it to cook some teriyaki chicken. Below is a picture of me using it to reflect and focus the infrared radiation coming from a space heater.
Although I considered the trash can lid mirror a success, I was not sure it will be useful to schoolchildren in India. I wanted to develop a smaller mirror for classroom use. After several attempts I found coffee cans work well. I also experimented with different systems for changing the pressure. The Vacuvin still worked well but you had to use your mouth to blow air in to make a convex mirror. I got an idea while they were taking my blood pressure at my optometrist. I looked online and found replacement bulbs for sphygmomanometers. This one also can be used in reverse.
I attached a flexible tube to the coffee can and gave this a try. It worked great. It was very illuminating to see how the image changes as you go from a flat mirror to a convex to a concave. Here is how it looks:
This seemed to be a good solution for an inexpensive large mirror that can be used in the classroom for curved mirror activities. Since the mirror can be created by just blowing in the tube, the most expensive component was the tape. Large syringes also work but you need to kink the tube between multiple pumps with the syringe.
I presented the mirror project at the March PTSOS workshop. I later heard from one of the teachers that had their students make and use trash can mirrors. He apparently was able to manage the safety issues that arise when you bring these out into the sunshine. I am still hoping to make s'mores with my students this year. The space blanket mirrors also drew interest when I used them for my show and tell at the Spring NCNAAPT meeting.
I have more ideas for space blanket mirrors. Instead of a coffee can I will make a cylinder/piston device. A ring would hold the space blanket and seal it at one end without needing tape. A piston and gasket would seal the other end. You could move the piston up and down to create concave and convex mirrors of different focal length. This would make it easy to replace the space blanket material that does wear out after a lot of use. Looks like I need to visit TAP Plastics. This summer I am helping with The Lowell Observatory Eclipse Experience at Madras High School in Oregon. In addition to bringing my spacetime simulator, I am going to build a large convex mirror using a 4' wide kiddie pool. It should give a horizon-to-horizon view of the sky during the festivities and the eclipse. You should come by to check it out!
When my students make their crash cushions many of them create paper tubes. This can lead to a successful design or a horrible one. I saved one such simple design and tested it in three different orientations. Depending on the level of your students you could show them this to aid with their own design development.
Several years ago Dan Burns and I started discussing an engineering project for which students build a crash cushion to investigate momentum and impulse. Using only a few sheets of paper and hot glue student groups design crash cushions (similar to water barrels or guard rails on roadways) to lower the force experienced by a cart rolling down an incline that crashes into them.
Since then we have both completed the project with classes albeit differently. We also presented at the Summer 2016 AAPT meeting in Sacramento, all of the materials discussed there are here. I wanted to share the project here again, with the tweaks my partner Jon Brix and I have made to it since.
My colleague Matt Miller continued the project in Conceptual Physics this year although opted not to use the Vernier sensor that I had last year. He opted for the resettable Drop N Tells I bought years ago instead as it is more visual for the younger students. He set up a ramp and used a lightweight impact car that had an additional <200 grams of mass added. Miller adjusted the ramp set-up until the 25, 15, 10 and 5-g sensors were consistently tripping. His students were challenged to design the crash barrier that did not trigger all the sensors. I believe he set the grading up this way:
C = triggering the 15, 10 and 5-g sensors
B = triggering the 10 and 5-g sensors
A = triggering only the 5-g sensor
Extra Credit earned for not triggering any sensors.
Dan uses a PASCO Smart Cart while I use Vernier sensors. The first year I tried this I used a low-g accelerometer because it was what I had. Through a Donors Choose grant I was able to purchase the higher 25-g accelerometer, 3-axis accelerometer and a Wireless Dynamic Sensor System (WDSS). The wired sensors require some coordination to prevent the cord from catching but are workable. I found that the wireless WDSS made for easier set-ups but would disconnect occasionally. Both the WDSS and the 3-axis sensors were almost too accurate and the graphs produced were difficult for students to interpret. I opted this year to use the single-axis 25-g accelerometer because even collecting 500 samples per second the peak accelerations were easier for students to determine.
In the past I've used a wood ramp and a big heavy dynamics cart that then travels along the flat lab bench into a wall. The transition from ramp to flat tabletop caused additional acceleration peaks so we opted to have the cart run directly into the wall from an incline. The heavy cart and steep ramp produced a high acceleration that exceeded the accelerometer's limits. We decreased the ramp angle and still occasionally "missed" the hit because the time of impact of the cart against the wall was so short. This year we opted to use a low-friction (not smart) PASCO cart and track from another colleague. The 120 cm long track was raised above the table by one textbook and pushed against the wall. A box of weights (over 30 lbs) was pushed against the higher end of the track to prevent it from moving. In initial tests the conservation of momentum caused the track to move quite a bit when the cart struck the end of the track.
This year student designs proved very successful. Because of the light cart and small incline students were able to reduce the acceleration of the cart at impact fairly easily. Usually the designs that "failed" did so because the cart passed underneath the crash cushion and still struck the wall. I had only one set-up in the classroom so groups took turns testing their barriers and collecting data. We stored a trial of the cart running into a book at the end of the ramp and then printed out graphs for each group with their trial on top of the control data. Here is an example of the data student's received with the control (green) and their trial (blue):
Students were to take measurements of their crash cushion before and after their collision although most cushions did not permanently deform. For some reason students were very pleased when their crash cushion suffers little damage; several cited the fact that it could be reused as a positive attribute. Students were also to calculate the Force with and without their crash cushion based on the mass of the cart.
Using this information students were to write a Claim, Evidence, Reasoning (CER) conclusion to answer the question: "Was your crash cushion effective?" After grading these conclusions we realized a few things: 1. Students did not agree on what made a crash cushion effective. Most students realized that decreasing the force, as shown on their graph as a decrease in acceleration, by increasing the time of impact made for a successful crash cushions. A few more realized that stopping the moving cart without letting it bounce back was also good. Yet many students considered their crash cushions ineffective if there was any acceleration, even if they reduced their force by more than 50% . 2. Students do not know what is fact vs. opinion. This must be going around recently. Students often stated opinions or qualitative observations in place of specific measurable data. "Our crash cushion was good because it stopped the cart slowly." 3. Some students did not understand the graph axis, significance of peaks, etc. Referring to the example above, some students incorrectly described the "time of impact" to be just over 2.5 seconds for the control trial. They did not understand or forgot the fact that the cart had to roll down the ramp before the impact. 4. When in doubt, students are prolific. I expected three, maybe 5, sentences from students yet often received a full page. While grading these conclusions I often crossed out over half of what was written because it was superfluous. They seemed to just keep writing and praying for partial credit.
Before handing back their conclusions I reviewed the CER format with students and showed them a few pictures of correctly written (short) examples of their peers. I showed them a few sample graphs from their trials and reviewed the significance of each peak. In the future this will be done the day after to give students a chance to correct their CER conclusions before turning them in.
Much of the tech world is abuzz with Elon Musk's announcement that Tesla will be producing glass solar roof tiles. They look as good as normal tile or slate or other roof materials but they are inconspicuous solar tiles. There are tons of articles out there but this video posted to @TeslaMotors twitter page caught my eye:
A kettlebell (I assume at least 10 lbs) is shown falling directly onto each tile sample being dropped from the same height and edited to be at the same time. The different materials respond differently; while the solar cell may not be functional after such a hit it structurally remains in one piece unlike the others. But I was caught by the varying rebound heights. I downloaded the video and opened it in Vernier's Video Physics app on my iPad and started playing with it. This is the first time I had used it to follow an object's entire motion so its not the cleanest. I tracked the first kettlebell that fell onto the Terra Cotta tile on the far left:
I plan to use this in my energy unit. I can ask students to discuss the change in potential energy for each of the kettle bells as they fall. Students could look at the rebound height for each sample and discuss the loss of energy in each case. I'm hoping students will realize that the loss in potential energy means that the energy has gone elsewhere. You could discuss common product testing, brittle materials vs elastic ones, momentum and more. If you have one-to-one devices you could have students do the same analysis for each material so that they can get the same information for each.
I've written about making simple PVC dart gun shooters and how to use them in the classroom with NGSS. I just did this lab with my Physics students, after their projectile unit test because they did not have to calculate projectiles shot at an angle. It was a way to work in a design challenge with my students while letting them explore angled projectiles.
Students were shown how the shooter works and asked to find the largest horizontal range. They were to record their angle, launch height, etc. and discuss the design changes in between each trial. No additional questions, no conclusions, just a quick and fun experiment about experimental designs.
"Can we stand on the tables Mrs. B?" Sure!
"Can we pull the balloon back all the way?" Sure!
"Can we cut the straw?" Sure!
They just had to record how far it went and how they changed their experimental design.
Seven classes did this lab between my partner teacher and I, usually students worked in partners, spread out across the quad of our campus. We had a running record during the day to see who could in fact make it the farthest. The first few classes hit 38 m, later classes had an unconfirmed 53 m but the largest confirmed was about 45 m. Doing the experiment with so many older students we ran into a few new problems I'd like to warn you about:
Use brand name bullets.
A quick Amazon search brings up lots of refill sets for the small Nerf bullets you need. We opted for a knock-off brand and got 200 bullets for $20. We expected to be set for life as I had previously only broken one Nerf bullet out of 20 with three classes of freshmen testing it last year. We were wrong. Bullets would tear after a single firing, the orange tip would come off upon impact and sometimes even just indentations on the side above the straw was enough to get poor results.
Have extra balloons.
Some of my football players decided to get into a "who can pull the balloon the farthest" contest and frequently broke their balloons. Sometimes it just happened in the course of the experiment. Have lots of extra balloons on hand to repair shooters with duct tape. We tried to use the same size and same thickness balloons for consistency. A few students noticed that the replacement balloon wasn't exactly the same length as before and might change their experiment.
Careful with metric tapes.
I have one 50 meter windup tape, nine 10 meter windup tapes and one trundle wheel. By the end of the day I had to completely unwind the 50 m one in order to rewind it correctly and we were down two 10 m tapes. Students did not understand how far 10 m was and would run out the tape with such vigor they broke the internal spindle of the tape. They can not be wound again, if you shake them you can hear all the broken plastic pieces rattle around the inside of the case.
The trundle wheel was far superior for measuring and was easier to reset in between trials. Although I did have one student hole the trundle wheel at arm's length straight out parallel to the ground and asked how it worked. He kind of sighted along it, maybe he thought it was a laser level??
This is one of those easy things to make that students get excited about. An easy set of review questions can be turned in to a kinetic activity for students. Students use the boards using a small circuit made of a light bulb and a small battery. I use a bulb and wire cut from an old strand of Christmas lights and a AA battery. Students connect one end of the wire to the hole near the question, for the orange vocabulary one on the right for instance they would hold this wire to the hole under #1. That wire connects to the light bulb and to the battery and the other end connects to the answer choice the students use. If their answer is wrong, the light bulb won't light up. If they are right and choose D. Ampere the light bulb will light!
These are easy for you to make or for your students to make. You can use use either card stock or a manila folder, the advantage of the manila folder is that the back can be hidden. You or your students must write questions with multiple answer choices on the front of the paper. Ample spacing will be necessary. Using a single hole punch, make a hole next to each question and near each answer choice.
Cut small strips of foil half an inch wide. On the back of the paper connect the question to the hole of the correct answer choice so it covers the open hole at each end. Be sure this strip doesn't block any other holes. Cover the strip with masking tape, it's easiest to cover it by matching the length of the foil to the length of tape. Put a small piece of foil behind the other answer choices, this foil can block more than one answer choice as long as it does not touch the correct answer choice foil. Again cover with masking tape. From the front there should be no differences in the look of the multiple choice answers.
On the left the orange example board is the vocabulary matching one shown above. In this type the insulating masking tape is important so that the light bulb only lights when the correct term is matched with that question. The other answer choices not used are given foil and tape but aren't connected to the question side and thus will never light the bulb if chosen. On the right a close up of the example one I added red circles to show you where the original hole punches are. Make sure the foil you added to the wrong answers (so that they don't look any different from the front) don't touch the piece of foil that connects the right answer to the question.
This takes a small amount of prep but the engagement is much higher. Students are more excited to check their answers to problems when they can visually see the light bulb light up. You can also use a small electrical buzzer the same way. How else do you think you can use this technique?
During our unit on torque and center of mass students hang meter sticks from ring stands to find their center of mass. But these meter sticks have one end wrapped in lead solder so that the center of mass is not at 50 cm. Students hang the meter stick from a fulcrum they could shift and added weights to the other side of the meter stick until it was level. They complete at least three trials to determine the unseen center of mass.
While this moves the center of mass considerably I have two problems with it:
1. I was a little concerned about exposed lead solder so I wrapped each hunk with electrical tape. Once I put the solder piece on students were not to move it. Sometimes students listen, sometimes they don't.
2. Students did not think about the lead solder as part of the meter stick, as if it had a heterogeneous mass distribution. They thought of the mass as an added weight and when drawing force vector diagrams might label an applied force at that point. Or students would draw the Force of Gravity of the entire meter stick as coming from this point, not from the center of mass.
I bought sticks that were very similar to meter sticks but not quite the right height. I planed them down a bit so that they fit the meter stick holders I have. Then I drilled lots of holes into them.
I tested one stick and found that drilling holes on one side only shifted the center of mass about half an inch. I needed to add more mass to one side or remove more mass from the other. I decided to add melted lead solder into each hole. I put tape behind the holes on one side of the stick and then used a soldering gun and iron to melt the 50-50 lead solder into each hole.
One of the trickiest parts was trying to keep the puddles of solder below the top of the hole. Its not a big deal if it bulges over but the next tape step is easier if its level.
I had one stick that was my sample stick, for instance now I know not to try a spade bit as it will crack the wood. On this sample stick six or so lead filled holes on one side of the stick shifted the center of mass considerably. In the bottom right you can see the original center of mass point with empty holes marked beneath the pen and the new location of the center of mass once they were filled with lead shifted to the left a few inches.
So I had a lot of holes to fill with lead. It took almost two hours to fill 184 holes on these sticks. Every stick has holes on one side (left picture), some of them also had empty holes on the other side (right picture). The majority of the weight shift is due to the lead but taking a bit of wood out of the other side helps a bit. Each stick has a different amount of holes so that the center of mass will be different.
The lead filled hole side got another piece of masking tape covering the lead. This helps with the illusion that the stick is homogeneous even when its not. And it will help protect students from the lead. I looked up the hazards of lead solder and the main issue seems to be ingesting lead dust from your hands after working with it. Washing your hands after working with it seems to make it perfectly safe.
I plan on using these sticks as part of a lab practical. Students will have to balance the sticks with a set fulcrum position. I can nail the hanger that acts as a fulcrum into one position so that students can't move it. They will conduct a few trials with different masses on the other side (empty/ no hole side) in order to calculate the position of the center of mass. By labeling each stick and keeping a key I will be able to check my student's work. I'm hoping these new sticks will prevent some of the misconceptions involved with this lab.
I have a ripped apart, non-working toaster and I want to use it to show my students a by product of electricity is heat. Since I took out the controlling circuit board and detached the plug I needed to hook it up to a voltage generator. When I first played with the toaster I was able to get a bit of heat but it was cumbersome to hold the wires and hold the toaster up for students to see.
I mounted the toaster to a piece of wood with two screws and added an angled piece of wood underneath so that it would be easier for the class to see. The toaster is actually on its side; the white plastic piece is the carriage that moves the bread up. I opened one side so that the heating elements were easy access. I soldered two alligator clips to the wires so that it would be easy to connect to the voltage generator.
Since the toaster isn't connected to a standard 120-V outlet the filaments don't get red hot. You can feel the heat near the filaments but the whole point of this demo was to show an entire class how it worked. Taking the time to (and the risk of) students putting their hands near the toaster wasn't going to work.
I hooked up the toaster to a voltage generator and used thermo paper to "show" the heat. Of course a heat vision camera would do the job nicely as well. I have three different temperature ranged pieces of thermo paper from Educational Innovations: 20-25 °C, 25-30 °C and 30-35 °C. The first was too low to be useful but the other two when held near the filaments showed the heat coming off the coils. I held the paper with a binder clip, not because it was hot near the toaster but because I was hot. *badum ching* Seriously, my own body heat would register on the thermo paper (as seen in the upper left of the last part of the clip) and thus would affect the visual.
Some of you may be worried about mounting an exposed toaster that gives off heat to a piece of wood. Don't worry, I checked and its okay. I left the toaster on for a few minutes then after I turned it off I used the 25-30 °C thermo paper to visualize the heat still coming off the filaments and then below them on the metal that actually touches the wood. No heat registered on the metal against the wood.
When I teach the law of conservation of energy I talk a lot about roller coasters, as most physics teachers do. Assuming a frictionless roller coaster we can discuss how drops in height reduce the gravitational potential energy and increase the kinetic energy while the total amount of mechanical energy stays the same. Students can use PhET's "Energy Skate Park" simulation to create a roller coaster with two hills, the second lower than the first like pictured:
I like to show students the bar graph and pie charts to illustrate how the energy changes from one kind to another yet the total remains the same. Measurements can still be taken, calculations can still be done but its still not something they can experience and observe directly in my classroom.
I've tried a few different things to create roller coasters in my classrooms: clear tubing with a marble, Hot Wheels track with a small car, paper folded tracks with marbles, etc. Each has their own pros and cons and I'm sure they work great for many teachers. But I want to be able to set up a roller coaster quickly, use it repeatedly and get consistent results. I may or may not take measurements with it but I wanted a visual of this type of problem to use in my classroom that could be set up in moments.
I bought two 8' pieces of wide aluminum U-channel from the local hardware store. I put my blow torch in a pot with brick in it so that it stayed upright and left my hands free. Donning thick leather work gloves I lit the torch and held the U-channel in the flame. It took a minute to get hot enough that it could be bent. I moved from one side of the U-channel to the other because a foot or so on either side of the flame became too hot to hold.
Some bends were difficult because the aluminum was hot or the position made it difficult to get leverage. My leather gloves were not as insulated as I would have liked. This pair now has permanent burned indentations. My hands weren't burned, exactly, but were sore afterwards for sure. My first piece of aluminum ended up in a much different shape because I didn't lay out which way I was bending it ahead of time; I'm still messing with that one.
I also found that while bending it down with the open side up was easy, like an upside down U, sometimes bending it up could cause the channel to buckle. This meant that I had to straighten the sides; I tried doing this two different ways. Some deformation was slight enough that I could bend the side back using pliers. For more serious buckles I inserted a piece of wood that was the same width as the U-channel and hammered it on the floor.
In the end my second piece of channel ended up making the shape I wanted. While I was able to get it to stand up here on the grass I had to use clay to get it to stand upright in my classroom on my front table. I can run a marble from the top of the larger hill through the track and it makes it over the smaller hill, somehow amazing students. A ping pong ball can also be run on top of the U-channel to make it easier to see.
I wanted to make a permanent mount for it so I didn't have to hold it up or use clay to hold it in place. I went through a few different iterations of mounting. First I thought I could just drill a flat head screwed into the track. That wouldn't work on the ends though that are nearly vertical to the horizontal. I also worried that even a flat head screw would affect the marble sent down the track. I cut a few inches off the first track that I had bent incorrectly and tried splaying out the sides with pliers. Splaying the sides out did not hold the track securely.
My next attempt was to create a vertical piece with a cut out that fit the track. I ended up using 4"x4" pieces of wood that were large enough not to need a cut out. The ends are free and not resting on the table which is not required for the ball or marble to roll down it anyway. The pieces I have are about the right size without being cut. The simplest solution has turned out to be the best!
In order to use it, all I have to do is place the two posts out and set the track on it. The aluminum U-channel is light and while it is over 6 feet long it should be easy enough to store on top of some cabinets. Now I have to try and rebend that first track into something more interesting ...
