Sunday, December 13, 2015

Periscopes take 2 ... well 3

After I wrote the "Down Periscopes" post I bought more PVC, more plastic mirrors and planned to make a few variations of more periscopes. The 4" diameter PVC pipe I used the first time was a bit large and cumbersome for in-class demos if I wanted to use more than one at once so I decided to go with a smaller 1.5" diameter pipe. I had bought scrap plastic mirror from TAP Plastics and planned to cut them down to fit into the smaller PVC pipe since they didn't have pre-cut mirror pieces in a smaller size. My first cuts were too long to be at a 45-degree angle within the right angled ends. Life got in the way for a few weeks and when I went back to it after some home renovations, I hit a construction snag. We had managed to burn through, blow up or break the motor shaft of three different Dremel multi-tools during the remodel. Without a tool to make a clean cut on the plastic mirrors I opted for one inch square glass mirrors I already had in my class room. (I've already admitted to being a hoarder of potential equipment.) My son wanted to help, he thinks all my PVC parts are his building blocks.

I've made three different periscopes of the same length:
1. A periscope sealed on the end that goes into the water and is thus filled with air. (This could be sealed on both ends as with the original but it is not necessary.)
2. A periscope sealed on both ends and filled with water.
3. A periscope not sealed on either end which allows the water to fill it.

The periscope to be filled with water has a hole in it that fits a rubber stopper. I was surprised how much water the periscope took and you do have to rock the perisope back in forth to move the bubbles around. The periscope has to be filled with enough water to submerge both mirrors. I also quickly found that the hot glue leaked on the "sealed" ends. But the leak was slow enough that I was still able to conduct the experiments initially.

On the left, viewing a small tiger toy through the air filled periscope
and on the right viewing it through the water filled periscope
without both mirrors submerged. 
I put a few of my children's toys in the bottom of a bucket with a light directly above me and viewed the toys through each of the periscopes when holding the periscope vertically. I expected the air filled periscope to give a clear image of the toys as with the original, and it did. When I looked through the periscope that allowed water to get into it I could only see the surface of the water in the tube and a vague bit of color.

I expected the water filled periscope to be blurry, and it was, looking about the same as trying to view something under choppy water from above. The pictures were difficult to get with a camera phone as the images in the eyepiece mirrors were quite small. I found that the water level had dropped in the water-filled periscope so that only the bottom mirror was submerged. I had to try holding the periscope horizontally to keep both mirrors submerged in water. I found that the toy could not be directly underneath the mirror and be seen out of the other end.

At first I thought it was refraction, but the medium did not change as the light traveled from the water in the bucket to the water in the periscope. After thinking about it for awhile I realized that although I had planned to hold the periscope horizontally as per the picture below I did not hold it perfectly parallel to the floor. This would account for the apparent shift in position as the mirror was aimed at the toy but not directly above it. Now I'm happy my husband tried to take an "embarrassing" photo of me experimenting in my pajamas.

I did recreate the water filled experiment being sure to keep the periscope more horizontal and found the mirror to be nearly right above it. After some trial and error, a better camera and more caulking on the water filled periscope, I was able to get clearer images.

I found that even with caulking on the ends because the clear plastic circle sat on top of the 90-degree elbow instead of inside it as with my other model it was never going to be perfectly sealed. When I presented this at the Fall 2015 NCNAAPT Meeting & Conference at Sacramento State my water-filled periscope leaked quite a bit.

Through that presentation I was able to refine my plan for using these periscopes in class a bit more. Several members enjoyed playing with my periscopes but then asked, "These are great, but what are you going to do with them?"

I've decided that the best use of my periscopes is as a discrepant event. Students can either look through the periscopes individually or the image can be seen through a document camera. I can show students the view through the air-filled periscope which produces a clear image. Then I can show them the view through the periscope open to air and water which produces a blurry image. Based on these two experiences I can ask students what they would expect to see from a water filled periscope. After they have a chance to discuss it they can actually see the image through the water filled periscope which is about as clear as the air-filled periscope. I hope to lead this into a discussion about refraction.

The air-filled and water-filled periscopes produce about the same image because there is no refraction between the object, mirrors and then your eye. (Consider the small change through the plastic circles to be negligible.) Only in the periscope open to water and air do you see refraction at the water-air boundary that affects the clarity of the image you see.

Tuesday, November 24, 2015

Engineering A Dart Launcher

We have five Nerf-obsessed neighbor boys who regularly have team turf wars across our neighborhood. It is adorable and we always find the small foam darts tucked under bushes and shrubs. My two year old finds them all the time and triumphantly brings them to me (they have a "return" pile set aside). One of our neighbors was playing out front with a two foot white pipe and while I watched he launched a small dart easily 40 feet in the air! Needless to say I was interested, if this was a store made toy I knew what was going on my Christmas list.

I called him over and he was more than happy to show me. He had made it at a birthday party recently; I made a mental note to forgo goody bags the next time one of my kids' had a birthday. His PVC pipe is probably 3/4" diameter and had a balloon duct taped to one of the pipe. He had stuck a straw into a form dart and held it in place with more duct tape. My neighbor's model had camouflage duct tape down the side ("That's to look cool," he told me) and two straight end connectors on each end. He let me give his a go and I determined the end pieces were not necessary. Each time I played with it, ahem, experimented with the dart launcher I was surprised at the height it achieved.

It didn't take long for the dart launcher to catch my daughter's attention and she asked, "Mommy can we make one?" Well who can say no to that? I had already been taking a mental inventory of the PVC I had on hand so we headed to the garage. I sent my kids to find Nerf darts and I found two pieces of PVC that were too short for other projects. By the time they returned with Nerf darts I had procured straws and balloons. I cut the straight necks off the balloons and duct taped them to the ends of the PVC. The foam darts were put on to the straws and taped together. All in all it took me five minutes to build two launchers.

I did vary the launcher for my two year old for safety as seen above and left. His PVC pipe was much shorter and there was not as much give on his balloon. I pulled the balloon farther up onto the pipe so that it could not be pulled back as far. I also used a larger and heavier dart on his straw so that it wouldn't be able to go as far. Of course, he had trouble actually launching it anyway so I shouldn't have been too worried. 

My kids and our neighbor that had inspired it all happily ran outside to play with them. Our neighbor found that he could launch his original lighter dart in my son's "toddler safe" launcher just as high as his original. He liked the more compact version for mobile combat and spent the next hour running around the yard with my daughter chasing their darts. You can also launch a foam dart without a straw but it does not go as high as one attached to a straw. I was so impressed with the height of the darts I started thinking about how to use it in my classroom. I know, that probably comes as no surprise.

I found a simple plan on a "Frugal Fun 4 Boys" blog that was similar to what we had made. I decided that since the dart launcher has several launching variables I wanted to use it as an engineering activity. I wrote up an activity (remember its a draft format!) that explained how to make the small launcher and outlined an all-class competition. The plan is assign one launch variable to each group: launch angle, balloon pull length, dart weight, straw length, etc. Each group will test the variable for maximum dart range using identical launchers and then report their findings to the rest of the class. Ideally they are also practicing some data collection skills by being careful not to change anything but their assigned variable. The whole class should be able to summarize these findings and determine the best set-up for their dart launcher to achieve maximum dart range. I'm hoping to then test each class' optimum set-up against each other in an all-class competition. I won't be teaching projectiles until the beginning of second semester but I will let you know how it goes!

I plan on purchasing a few of these refill packs so I don't have to diminish our neighborhood ammunition supply.

Sunday, November 15, 2015

Dank memes

It's impossible to participate in social media without being inundated with images emblazoned with captions that overlie the images. These are not factually captioned photographs. These are humorously graffitied screen-captures or illustrations commonly referred to now as Internet memes ("meems"). The term, meme, refers to something else.

They are a sort of lexicon in Twitter, Facebook, and the like. A cultural fad, or here to stay? Who knows. In the meantime, I dipped a toe in.

I was first compelled to create a few in support of my "Equation, Rearrange, Substitute, Answer" recipe for students to use when solving problems. But the craft is limited only by one's creativity and comedic skills.

After posting a few in class, students wanted to join in. But they don't always have the same sense of decorum and propriety that sets boundaries on what a classroom teacher might feel comfortable posting.

One student aficionado referred to top-quality caption/images as dank memes ("may-mays"). I thought he was making it up until I found an online urban dictionary pronunciation. Dank meme can also be a sarcastic term for old / overly done memes.

When creating memes, the reflexive urge s to create "nag memes".

Encouragement meme are harder to produce. The encouragement element cuts against the sarcasm/humor element. One does one's best.

But wait. Why not make some with a physics theme?

I think it's important to "save a blade for yourself". It's no good to criticize the world with nag memes while holding yourself above the crowd. Easy? Yes. Comforting? I suppose. Good? No.

It's important to remember in all cases where social media and teachers intersect. I'll illustrate with news item headlines:

Teacher awarded prize for poignant Facebook post

Teacher fired following controversial tweet

One of these headlines is plausible. The other will never appear above a real news item. For teachers, there are two outcomes possible when participating in social media: nothing or negative. There are no positive outcomes. Only negative. Or—at best—none.

I generally trust colleagues to their best judgment to avoid creating memes that border on racism, sexism, etc. But at the last YouTube Physics session I hosted, a colleague traveled to The University of Minnesota AAPT SM14 and come to the session just to share this gem, which he thought was a great thing to show students in a physics class. So… yeah. If AAPT ever does a YouTube Physics session, it would probably be best not to use the "open mic" format.

So remember,

And be careful. You'll do better connecting the message to students if you know what the common use of a particular meme is. Once you know what the standard use is, you can bend it to your own use.

Here is a Dropbox link to the memes I've created: Memes

And I would be remiss if I didn't provide a link to Buzzfeed's 61 Best Teacher Memes.

Wednesday, November 11, 2015

Mysteries of Millikan

Robert Millikan's 1909 oil drop experiment is an American classic. It won Millikan the 1923 Nobel Prize in Physics. It spawned Paul Allen Stokstad's COmpany, PASCO. It made a surprising appearance in David Goodstein's Mechanical Universe, despite electron charge being decidedly non-mechanical. It's a great episode in that it elucidates the nature of the process of science (while debunking the overly simplified but easily posterized "scientific method").

We do not conduct the experiment in my high school physics classes. But we do watch the episode of The Mechanical Universe. And we do a very dry-labbed worksheet, originated by my mentor at Ann Arbor Huron High, Walt Scheider: The Millikan Oil Drop Experiment.

But before we do any of that, we solve a related quantization puzzle. Lab groups are given a set of numbers that could have been obtained by measuring the mass of various numbers of identical balls in a container. From the numbers, students must determine the mass of a single ball and the mass of the container.

Once the students have done that, we measure the mass of actual containers of various numbers of drilled balls. I'm a huge fan of drilled balls—every physics classroom should be rich with drilled balls. We measure the masses down to the grams and students get good results.

[Hint: don't use fewer than three balls in the lightest set and vary the number of balls by 2 and or 3 (but not by 1) between sets.]

Here's the worksheet for that. Millikan Mystery.

Faraday Cage Fight

Since I'm in a new-to-me room that was once an English room, I keep running into equipment pitfalls. For my electrostatics unit I realized that I needed a safe space to set up my Van de Graaff machine. All my tables and desks have metal legs and edges but I have one built in wooden desk. It was very close to my class phone, clock, LCD projector and laptop so I was concerned. I reached out to the PTSOS listserv and it was suggested that I build Faraday cages to protect my electronic equipment from the static charge produced by the machine.

I thought it was brilliant and happily popped over to my local hardware store to purchase a few rolls of 1/2" grid pet fencing. I used diagonal cutters and cut a piece large enough to fold the edges down and make a five sided box to cover my projector and laptop. I have a few suggestions for safety though, if you decide to do this yourself:

1. Wear gloves, a long shirt and pants you don't care about. The sharp cut ends not only snagged my pants but made me look like I had lost a fight with a couple of cats. I was asked for a week what I had done to suffer so much damage.

2. Wear Safety glasses. I often cut some small pieces off of the ends in order to try and minimize the rough edges. After a few small pieces zinged past my head I realized I should have worn safety glasses.

I decided to test the box by putting my cell phone in it and calling it from my classroom phone. If the Faraday Cage was working properly it would interrupt cell phone reception. I was disappointed that my cell phone rang but realized there was not a bottom to my box. After some research I found that a sheet of aluminum foil underneath it would do the trick. I tried it again and my phone was silent! My Faraday cage was ready. I did have to place a weight on the top since the cage was tweaked a bit.

Since my laptop and projector worked reliably during and after the Van de Graaff machine was on I would consider this protective measure a success. I was surprised though when my first class of the day started calling out, "Look at the clock! It's wigging out!" And indeed it was. The clock flashed several wrong times, seemingly without pattern while the Van de Graaff generator was on. I tried to make a smaller Faraday cage for it but there was still some interference because there is not a "bottom" to the Faraday cage since it is mounted directly to the wall.

More Blog of Phyz Faraday cage fun can be found here: Faraday Cage: AM vs. FM.

Van de Graaff Fun

Shocking children—in all ways—is very enjoyable for a physics teacher. I love the days that I can surprise them and nothing surprises them more than small electrical shocks. I have at least one day set aside in my Electrostatics unit for fun with my Van de Graaff machine using a structured question, prediction, test format. I start with making my hair and a few chosen students' hair stand on end while standing on the insulating stool. I move through a few demonstrations (full write-up available here) and ask students to apply what they know to each new scenario. We always have time for some fun afterwards which usually leads to some students shocking others.

This year I had a particularly enthusiastic group that wanted to take pictures and even came in at brunch to play, ahem, experiment, with the Van de Graaff machine some more.

Students were allowed to make contact with others either by "ET Touch" (touching outstretched pointer fingers), holding hands or fist bumping each other. We soon discovered that fist bumping each other was actually more painful that an "ET Touch." We tried to be as judicious as we could using the same two students and allowing one to "charge up" for the same amount of time. Both students involved said that the fist bump was more painful than the "ET Touch," and multiple pairs of students in different classes agreed.

The sparks we created were much more visually impressive when fist bumping than any other contact.

There's probably a reason for that...

What's Really Warming The World?

Professional email listservs are treasure troves of good ideas and pedagogical sharing. I love them, and have been greeted by people I have never met before with "Oh you're that Bree! You're always commenting / replying / asking questions on [insert listserv name here]."

This link to a Bloomberg Business graphic called "What's Really Warming The World" recently came through one such listserv and I wanted to forward it to everyone I know. The Blog of Phyz seemed like a faster route.

The graphic and accompanying article discuss each of the most common suspected causes of our global climate change and general increase in global temperature. The data is based on the findings from NASA's Goddard Center for Space Studies.

The 1.4 degree temperature increase in our global temperature is plotted from 1880-2005. Each of the potential contributors is discussed in turn and their influence on the global temperature plotted. "Natural Factors" (orbital changes, the sun, and volcanoes) are discussed first followed by "Human Factors" (land use, ozone depletion, aerosol use and green house gases). I found the visual powerful and scientifically intriguing and that doesn't happen too often.

Click the link to the article: the graphs are large and animated. And compelling.

Sunday, November 08, 2015

Keeping the real Apple Keynote alive

Apple officially discontinued development of its first-rate presentation software, Keynote, in October, 2013. The final version was Keynote 5.3, and was originally released as part of iWork '09. So some people think of it as Keynote 09 or Keynote 5. (MidCap enthusiasts errantly refer to the program as KeyNote.) I posted a death notice/rant here.

Confusingly, Apple now produces Google-docs-esque productivity software, including a presentation program named Keynote (technically, Keynote 6). The vast majority of legacy Keynote users despise Keynote 6 for many, many reasons. Apple promised to throw extant users a bone. Too little; too late. Or never. Apple lost the thread on what Keynote was supposed to be, and I have to presume they'll never get it back.

My school district does its best to keep teachers' computers from aging into obsolescence, so my 2010 MacBook Pro 13" was replaced this week with a 2015 MacBook Air 13". My own computer is a 2012 MacBook Pro 15". Making the new computer useful to me was not a trivial matter. Since it's not my own personal computer, I could not initialize it as a mirror of my "old" computer or restore from a Time Machine backup. But I did need fully functional Keynote 5. And I needed Keynote 6 not to be there: among the disasters incorporated into Keynote 6 is its tendency to automatically "update" working Keynote 5 files into broken husks (misshapen, ill-fitting Keynote 6 files).

So I do have a paid-for copy of Keynote 5.3 with a valid serial number/license key. (When Keynote is open, click the Keynote menu and select "About Keynote" to see the serial number/license key.) But the new Mac has the new Keynote installed and does not have the discontinued, functioning version of Keynote.

Here's what I did to ditch the awful Keynote 6 and install the functional Keynote 5 on a new Mac that wasn't really mine.

Step 1: Delete Keynote 6. Drag it to the trash. Empty the trash. Putting that terrible code-cobble out of its mystery should be the very first that one does at first light with any new Macintosh. Yes, really. Flush it now.

Step 2: Download the disk image (.dmg) for the iWork '09 free trial. (It works as of this posting; nothing on the Internet is guaranteed to work forever in the future.)

iWork '09 Free Trial Installer

I found the link on this page.

Step 3: Run the installer and install the software. This will get you to Keynote 5.0. But you don't really want Keynote 5.0. You want Keynote 5.3 with all the improvements that occurred between 2009 and 2013.

Step 4: Find and run the iWork 9.3 updater. I found the updater on this page. (Same caveat as above).

Step 5: Register the software with your serial number/software key.

So far, so good.

I did run into another problem owing to my old fascination with fonts. It turns out, I own and use a grand symphony of fonts. Horses for courses. I thought I successfully created a Dropbox folder with all the fonts in my computer's Library. (You then drop all the fonts into the new computer's Library/Fonts folder and opt to skip all duplicates. But opening Keynote documents revealed that my new computer was missing fonts I used.

I discovered the location of these fonts was in my User directory. But when I opened my User directory, there was no Library folder to be seen. I learned that Apple, in its oft-to patriarchic tendencies, hid the User Library from Users. One way to work around this foolishness is to hold down the option key while accessing the Finder's "Go" menu. Second batch of fonts ferried over via Dropbox and… success!

Saturday, October 31, 2015

Michio Kaku: not a fan of US science educators

The first time I heard of Dr. Michio Kaku, it was when he was honored with the American Association of Physics Teachers' Klopsteg Memorial Award at the 2008 Summer Meeting in Edmonton. (I received a Distinguished Service Citation at that very same meeting, but the Klopsteg is much higher up on the ceremonial food chain and involves a plenary presentation.)

So it was disappointing when the AAPT honoree's Sacramento Speakers Series talk took an unfortunate turn toward the end. Kaku emphatically and unambiguously slammed American science educators for crushing the inquisitive nature of curious young students, ranking the US science education as the worst in the world. (Something tells me he's never been to a school in Burkina Faso.) This ham-fisted slam is a well-worn trope. I've seen it before. And it's not completely without merit.

The quality of American secondary science instruction runs the gamut. There's good, bad, and everything in between. And strictly speaking, the world is large: I don't think the US is dead last on any metric of science education. Still though, this disparagement is a popular chestnut. And other nations do turn in higher scores on standardized math and science exams, such as TIMSS.

Like nearly everyone else who charges US science educators with misguided failure, Kaku did not offer corrective measures. So I put him on the spot after his talk in the green room. Without any preface, I approached him and asked, with gentle bluntness, "So what should we be doing?"

He suggested that we should be teaching to students where they are instead of where teachers are, so as to better excite them about science. That is, we need to teach them lasers and GPS rather than friction. The physics of now, not the physics of 300 years ago. And the physics of movies is always good.

Nothing wrong with that at first blush. The physics of 300 years ago is the focus of most first semesters in most physics courses. Some like it to be the focus of the second semester as well. I'm not in that camp. I like to get into the physics of 200 years ago and 100 years ago. Quantum mechanics and relativity are 100 years old now, and we still refer to these topics as "modern physics". A hazard of modern physics is the dearth of workable laboratory experiences available to high school students.

The physics of movies includes much 300-year old physics.

It should be noted that when asked about his interest in ice skating, Kaku praised it as a pure expression of Newton's 300-year old laws.

It should also be noted that the many nations whose students outscore Americans in international math and science studies do not beat us because they are focused on the physics of now. Because the exams given in the international studies focus on the physics of 1600 CE—1900 CE.

I don't get the sense that Dr. Kaku has fully thought through his charge of US science education being the worst in the world. It's a easy charge to include in a public lecture, I suppose. It strikes me as lazy to make the charge without offering a solution. I don't think he's familiar with Next Generation Science Standards, but it wasn't a topic we were able to get to.

In any case, it seems Kaku will trot the globe announcing to all who will hear that high school science teachers in the US crush the curiosity out of previously inquisitive American students.

Now that I've revealed my new colors as "not a fan of Dr. Kaku" despite my generous introduction for the Speakers Series, I'll offer a few more areas for improvement. To the extent that they come across as petty, Kaku apologists can dismiss the entirety of my critique of his anti-educator slam.

A shirt I won't be wearing.
His PowerPoint slides used a canned Microsoft background, Helvetica (not Helvetica Bold, just Helvetica) for titles and Times for text. Several slides included too much text that was not necessary to make the slide's point. Asking the audience to read text while he's speaking is not an effective approach. Where were times (!) he used red text on a blue background. On the upside: not one instance of Comic Sans. Low-quality presentation slides grate on me because I work hard to polish the slides I use in my own classes. I make sure graphics and animations are there to support the story I'm telling, and I don't use much text. I'm telling the story; the preso is there to back me up, not to compete with me.

Kaku attributed the quote, "Predictions are difficult, especially when the future's involved" to Yogi Berra. The true originator of that quote, like many good quotes, is in dispute. But one alleged originator is none other than physics Nobel laureate, Niels Bohr. In the event of doubt, I'd go with Bohr because physics. I don't doubt that someone as intelligent as Dr. Kaku is unaware of the Bohr attribution and has reasons for going with Berra. But it strikes me as throwing Bohr under the bus unnecessarily.

At least three times (and probably more), he admonished audience members to "Buy my book!" In my own personal opinion, that's not a phrase that should be uttered from the stage. It didn't help that he suggested that those who bought autographed books tonight could profit by selling those books on eBay. Not something that I've seen classy speakers do. (Humorist and author, David Sedaris, actually reads from someone else's book from the stage and encourages audience members to buy that book. That's classy! And Sedaris still sells plenty of his own titles at each appearance.)

The Physics of My Future? I won't be asked to introduce Dr. Michio Kaku at any of his appearances. And if I were, I would decline. Not so much out of injured indignation. More out of respect for his low estimation of my profession. It does Kaku no good to be introduced by someone who's made a career of crushing the curiosity of US science students.

An unexpected delight: Working with the Sacramento Speakers Series

I am more likely to get things I don't deserve than I am to be denied things I do deserve. So there I was on a Tuesday night, introducing physics media star, Dr. Michio Kaku to an audience of some 2000 at the Community Center Theater, where he was the second celebrity in this year's Sacramento Speakers Series.

I was given the honor of being the introducer via my connection to Rio's Civitas program chair, Linda Reed. She works with the Series' "Share the Vision" program, which affords local high school students a special pre-show audience with the speakers. They get their own question and answer session with the luminaries. Quite brilliant, really.

Michio Kaku is well-known in the physics community as a prolific author and frequent media science expert. He's carved out a niche in prognosticating the "science of the future". He's very comfortable in front of the camera, and speaks with confidence and authority on the scientific topic of the day. This distinguishes him from most physicists, and it makes him a reliable media darling for journalists.

Kaku's presentations on how things will be in the future are captivating. I confess to not being well-versed in Kaku's expansive oeuvre. I even floated the notion of introducing Kaku to my physics- and skepticism-rich friendosphere on the off chance that Kaku advocated some weirdness that would set him outside the scientific mainstream. I didn't want to be heaping praise on anyone with a "Dr. Oz problem". No objections were raised, so heap praise I did. (The script of my introduction is in the comments.)

Everyone associated with the Sacramento Speakers Series was first-class and professional. They took very good care of me, and it was very groovy to hang out with the principal organizers, manager, Dr. Kaku, and ABC10's Cristina Mendonsa backstage in the green room. She's as personable as she is polished, and did a great job interviewing Kaku and managing the audience question cards. I made a point to personally thank Mitch Ostwald and each of the organizers who worked with me to facilitate my wee role in the evening. They are doing great work and adding to the cosmopolitan nature of Sacramento. [Photos courtesy of The Sacramento Speakers Series]

Wednesday, October 14, 2015

Lesson for a 20-minute class

Many of our students took the PSAT today at school. After the testing period, we ran periods 1 through 6 at a little more than 20 minutes each.

So we watched and answered questions about Top Gear's segment on the three-wheeled Reliant Robin.

The video is here:—Top Gear's Reliant Robin. The full segment—shown on the Wimp page—is 14 minutes; shorter edits can be found elsewhere (YouTube, etc.). I couldn't figure out how to embed Wimp's video into streaming here.

The questions are here: Rolling Through Roundabouts in a Reliant Robin.

Sunday, September 27, 2015

My "Information for Parents" folder, 09/2015 additions

I've created an Information for Parents folder in my Schoology "ecosystem" ("edusystem"?).

In it, I placed the information discussed in the post below. And links to

"Leaning Physics is Tough. Get Used to It" by Rhett Allain in WIRED

Yes, students learn physics by working on problems and by failing to solve problems. It’s the journey to the solution that’s important, not the solution itself. Using a video solution would be like using a golf cart to run 5 miles. Sure, you end up in the same place if you run or ride—but they do not produce the same results.


"Declining Student Resilience: A Serious Problem for Colleges" by Peter Gray in Psychology Today

We have raised a generation of young people who have not been given the opportunity to learn how to solve their own problems. They have not been given the opportunity to get into trouble and find their own way out, to experience failure and realize they can survive it, to be called bad names by others and learn how to respond without adult intervention. So now, here’s what we have. Young people,18 years and older, going to college still unable or unwilling to take responsibility for themselves, still feeling that if a problem arises they need an adult to solve it.

There may be a theme building here. And I may be overcome by the tide. But for now, I'm standing strong.

Sunday, September 20, 2015

What I did for Back to School Night #30

We started the school year (with students) on August 13th this year. That's a record early start date. Who remembers when school didn't begin until after Labor Day. Such places still exist. Just not where I teach.

Our Back-to-School Night was September 9th. For the past many years, I eschewed any discussion of policies for the 10-minute talk to parents. Instead, I presented a shortened version of the presentation I give in my Physics, AP Physics 1, and AP Physics 2 courses: "Physics Begins With an M". It's good stuff. And it would often generate at least one spontaneous round of applause at the 10-minute mark.

This time around, I spoke to the parents about the content of the course, how grades are determined, and the importance of engagement. The talk was not devoid of humor, but it was certainly heavier than my previous presentation.

I also upped the page-count of the handout I give to parents at the session. The hope is that the handout I distribute to parents who come in tells them everything they could want to know. That takes the pressure off the 10-minute session we have together. That said, I never open the floor to parent questions. Time is short, and that tactic has a great potential for failure.

Here's the handout I provide.

Back to School Night Parent Information

I also give them this:

How Not to Get Stuck on Physics Homework / How to Succeed in Physics.

And yes, my very first Back to School Night was in September of 1986. Ronald Reagan was President and California Governor George Deukmejian had a daughter at my school. He was at that Back to School Night, too. So this edition of BTSN was my 30th.

Dipping a toe into Schoology

Back in the late 1990s, I was keen to establish a presence on the nascent World Wide Web. I created pages with Adobe's PageMill in hopes of creating in a WYSIWYG environment rather than get bogged down in the intricacies of HyperText Markup Language (HTML).

By 2000, I was creating and posting Portable Document Format (PDF) files of my curriculum materials. That process is intertwined with meeting and befriending Paul G. Hewitt. It was in the early 2000s that I registered the domain name. In 2006, I started The Blog of Phyz.

In the late 2000s, my school district began providing a website generation service (SchoolWorld). I already had a relative "palace" on the web. By comparison, the district's service allowed teachers to create quaint cottages. I wasn't interested.

The district has discontinued its relationship with SchoolWorld in favor of a new relationship with SchoolWires. It also has an enterprise account with Schoology.

I'm exploring the utility and capabilities of Schoology. I use it primarily as an organizational tool for the curriculum in my courses. It seems useful in that regard. But nothing's as useful as the palace I've built at

One bright spot is the fact that tests created with ExamView can be exported to Blackboard format. Tests in Blackboard format can be imported by Schoology at online tests. Schoology can be configured in terms of test administration and the results are posted in class roster lists. Pretty slick! (It would be nice if ExamView showed any signs of life since 2012.}

In a way, it appears the logistics of Schoology make it possible to violate copyright law without interference or consequence. Only students and parents of students enrolled in courses can see the Schoology pages (and links and materials) associated with the course. So the violations are small-scale, I suppose.

Anyway, we'll see how it all goes. 

We could be evolving from an era of world-wide curriculum sharing on the web to closing back in ourselves. We shall see.

Monday, August 10, 2015

Professional development: Is it effective?

Trigger warning: if you are at all allergic to snark, you are advised to avoid this post.

It's that time of year, colleagues. You're rested up from that "summer off". [Please note: "Summer" is defined as the eight weeks between mid-June and mid-August, and "off" means you weren't teaching your subject in your classroom.] What better time to suck the life out of you with school-wide (if not district-wide) professional development (PD)?

According to thorough research collected by physics teaching superstar and Einstein Fellow, Marc "Zeke" Kossover, it turns out your professional development training may, in fact, be effective. But chances are that it's not.
A study of 25 professional development programs for math and science teachers in 14 states showed positive student outcomes if three conditions were met.
1. The programs focused on content in mathematics and science.

Honestly, you can probably stop right there. Chances are that the the PD you're engaging in is not focused on math or science. But if it is, feel free to continue.

2. The programs included on-site follow up in classrooms.

3. The teacher contact time reached at least 50 hours.

If the PD you're beginning this week meets all those conditions, please post a comment! To me, such PD is a unicorn: I know what it's supposed to look like, but I've never seen one in person.

In other news, I am beginning my 30th year of teaching this week.

Sunday, August 09, 2015

Canvas to Keynote: The End

This is the story, dating back to 2012.

This is a graphic history of the progress at various intervals.

The conversion is now complete. All extant curriculum documents are editable (by me, anyway) in Apple's Keynote 5. Of course, since this process began, Apple rebuilt Keynote "from the ground up". They defanged it so it could be a cross-platform (Mac OS X and iOS) app. For now, I'm avoiding Keynote 6 like the plague it is. We'll see how long I can do that.

For now, a weight has been lifted.

Thursday, July 23, 2015

FLIR ONE 2.0 "See the Heat" camera now available*

I'm a fan of photography and imaging. I do a bit of photography, myself. I am a fan of Harold Edgerton's high-speed photography and videography.

I jumped on Casio's EX-F1 when it came out in 2008, and recommended it to physics teachers. My friend and colleague, Dan Burns, got one and came up with a simple rule for what to record in high speed: "If it moves, shoot it!"

When I heard that the heat imaging experts at FLIR were developing a consumer-level product, I looked it up. They were selling FLIR ONE, a camera/case combination for the iPhone 5/5S. I had an iPhone 4S, so I didn't bite. When I upgraded to an iPhone 6, the FLIR ONE was still not an option.

At CES 2015, FLIR announced the next version of FLIR ONE. It wasn't a case, but rather an attachment that connected to the iPhone via the Lightning connector.

As I was beginning my journey to wilds of Alaska, FLIR announced that the new ONE was shipping. By the time I got back to order one, the wait time was up to about six weeks.

Poke around FLIR ONE page.

Check out the marketing video; it's stronger on the funny than it is on the informative.

Or this one. A bit more informative…

Flir One Review

*I don't know how back-ordered they are now, but the sooner you buy, the sooner you'll get.

Tuesday, July 14, 2015

A quick dose of physics fun with Captain Disillusion

CD's laser vision sees through all!

Quick D: Where Did the Ball Go?

If it seems I've been away from The Blog of Phyz, it's because I have been. In other news, The Treks of Phyz has been getting new posts and is due for more. Alaska was beautiful!

And I've been finishing the manuscript for the Conceptual Physical Science 6th edition lab manual.

And last night, I even watched History of the Eagles (Part 1). "How come?" you might ask.

I Can't Tell You Why.

Tuesday, June 23, 2015

Samsung's "Transparent" Safety Truck

They finally did it: a truck with an index of refraction n = 1.0. Well, no. But still, this uses readily available technology to do something very groovy.

This seems like a great idea. It should be mandated for any large vehicle (trucks, RVs) on two-lane roads.

Samsung Safety Truck (Versión en Español)

Samsung Safety Truck (Versión en Español)

Fragile floating rainbow whales

These ephemal bubble clouds flourish where the breezes are gentle and humidity is high. Small children delight in seeing them, but are also all to eager to destroy them. Still though, these amoeba-like examples of fluid dynamics, surface tension, and thin film interference are mesmerizing.

Giant Stinson Beach Bubbles

I especially love the longitudinal shot from behind the bubble master. The disintegration is magical.

Monday, June 22, 2015

Down Periscope!

Using the loosest form of the word, I am the advisor of our high school's AVBotz Robotics Team. These students are self- or peer-taught and exceed the electronics knowledge I can bestow on them in a regular Physics classroom. They have built an autonomous underwater vehicle (AUV) and compete in the International RoboSub competition every summer against universities such as CalTech, Cornell, Penn State, ASU, etc. (Notice I said universities!)

When the sub is being water tested some students are on the deck editing code on their computers at a safe distance from the pool while others are in the water to manipulate the sub and task props. At a recent water test we frequently asked the swimmers what the sub was doing since we couldn't see it in detail from above the water. The poor swimmers had to duck underwater then return up to say "It's heading straight," duck down and up again to say, "Now its dropped a foot," etc. as the sub was going through maneuvers.

It is probably the first time in my life I thought, "I need a periscope."

Although it wasn't the first time I had thought of building one. The Exploratorium's "Square Wheels" book of demonstrations by Don Rathjen and Paul Doherty has a project called "Periscope With A Twist." The instructions explain how to make a PVC periscope you can twist and see how the orientation of the image changes. I knew I would have to modify the design because I wanted to have part of it underwater. As light moves from air to water it refracts or bends because light waves travel more slowly in water. If I had used the original design the mirror I was looking into would give me a view of the water level within the tube but would not allow me to see underwater. I needed to seal the mirror with something transparent at least on the end that would go into the water. I decided sealing both sides would be best so I wouldn't ever accidentally dip the unsealed end in the water.

So I was off to TAP Plastics and got two of my favorite planar mirrors for a few dollars each. I was planning on cutting some transparent scrap to seal off my ends when I found pre-cut circles 4 inches in diameter. It required me to up my PVC pipe size but I found 4 inch solid PVC drainage pipe and two 90 degree elbows to fit. The pipe only came in 10 foot lengths so for awhile I awkwardly maneuvered my son in a shopping cart through Home Depot while holding the pipe vertically. (FYI the fine-toothed hack saw in the molding aisle is the best cutting option if you didn't bring a truck.) The TAP Plastics bill was $10; the pipe was $10 but I have enough for two more periscopes at least and the two elbow joints were less than $7. That makes the total cost of the raw materials to be about $20 per periscope.

I was pleasantly surprised to find that because I had increased the pipe size I did not have to cut the elbow joints to hold the mirrors as in the original plans. The mirrors fit nicely into the pipe and I was able to hot glue them in place (A). The hot glue job is not pretty; it was difficult to glue a rounded corner of a planar mirror to the inside a PVC pipe on a curve when I wedged all four corners in at once (B). But they seem secure! The 4 inch circles fit nicely into the elbows and a bit of hot glue secured them (C). There was not enough hot glue for me to feel that they were waterproof though. I used window caulking around the circles and the ends seem water proof (D). I used PVC glue between the elbows and the straight piece. I added some more window caulking along the straight pipe and elbow seam even though it was glued (E).

I had a periscope! Of course I had to test it out in a pool and my daughter was happy enough to help me out. As I expected the periscope is very buoyant, it is almost 4 feet of air filled tube after all. If you hold one end in water only one elbow will be submerged; it takes some force to hold more of the periscope under water if you would like to view objects deeper. If I had not been holding the periscope for my daughter it would have risen up too high for her to look through.

I do plan to make another periscope that is not sealed and not glued in place so that I can use it as the original project plans intended. There may also have to be a third one built for my kids; they don't like watching me make toys for school that they don't get to keep. Explaining this periscope alongside an unsealed one will bring up refraction, planar mirrors, image orientation, buoyancy and more!

Saturday, June 13, 2015

A giant eyeball… in your classroom!

When we talk about the refraction of light in physics it can seem abstract to students which surprises me since it is everywhere in their daily life. I like to bring up the convex lens of the human eye as an example and despite having a lot of AP Biology and anatomy students, they really haven't put the two concepts together. I model the way the eye works to my class by focusing light from outside our classroom onto a piece of white paper through a convex lens. I usually send a student outside to move around so the rest of the students can see his/her image and darken the room. The comments they make in disbelief are similar year to year: "He's upside down!" or "OMG its moving!" or my personal favorite, "She's in color!"

This year I added my own version of the Exploratorium's eye model exhibit using an old laundry room light. Since it was translucent white already, I masked off all but the top and spray painted it black. The original exhibit has a two foot diameter plastic sphere about the same shape that is clear except for a white colored portion the size of what I left white.

This demonstration would not work if I did not have a convex lens with a focal length that matched the height of the light. Luckily I had a magnifying glass that was very close and focuses an image on the white portion is held just outside the bottom of the light. If I push the magnifying glass right against the bottom of the light the image is not focused and it models how slight changes in focal length can create vision problems. (Although the focal length isn't changing the slight position change of the lens means that the retina isn't at the focal length and thus produces a fuzzy image.)

From there I show some basic images of nearsighted and farsighted lenses and discuss how their focal length varies. I ask students to decide if a convex or concave lens would fix them and we discuss how they would adjust the focal length by making it longer or shorter. Its interesting to take a poll of the class and ask who is nearsighted and farsighted; there are more farsighted than nearsighted people and it's rare to have a near-sighted student in class. Before I ask the students though I try to guess if they are nearsighted or farsighted based on the appearance of the eyes. A nearsighted person will have eyes that appear smaller since a concave lens is used to correct it; although it is easier to see if the sides of their face are closer together than the rest of their face when viewed through their glasses. A farsighted person will have eyes that appear larger since a convex lens is used to correct it.

And to bring in your more literary students you can reference the optics mistake in The Lord of the Flies. The character Piggy is described as being nearsighted (myopic) which would require corrective concave lenses. Early in the book Piggy's glasses are used to start a fire, something that could only be done by focusing sunlight from a convex lens. Tell your students to bring that up to their English teachers; it's cross-curricular learning!

Color subtraction—reflected color

They say necessity is the mother of invention and it's very true for teachers. I found myself wanting to do a reflected color (color subtraction) lab in my Conceptual Physics class that was observation based and introductory before a lecture. An internet search found nothing I could use so I had to come up with something myself.

NOTE: Any reflected color demonstrations or labs have to be in utter darkness. Any light from an outside source can be reflected off your object and will not produce the results you want.

At first I wrote one that used my light ray boxes and shone light through filters on a paper that students would color with Mr. Sketch markers. When I tried the experiment myself though, I wasn't getting the results I wanted using the filters. I turned to my trusty Inova Microlights in red, green and blue and found that they worked well when shone on the same paper but I didn't have enough for lab groups nor the time to get to an electronics warehouse that carried them locally. It was the night before I wanted to do the lab and I felt like a first year teacher not knowing what I would do the next day.

I thought if I didn't have a light source in the colors I wanted then perhaps I could make them using my computer. I started making images in the colors I wanted and trying to project them before I thought, "Someone must have done this already." Sure enough I found an app called Color Light Changer (free version) which did exactly what I needed it to. The program allows you to choose colors using either HSV, RGB or HEX color systems. To produce as colors with the right amount of red, green and blue as possible and for easy student manipulation I chose RGB. I set it up to produce red, yellow, green, cyan, blue, and magenta with little transition time. [See also RGB Colors and RGB Explorer.]

Now I had a reliable light source in the colors I wanted but I had to still find somethings that were the right colors to reflect that light. Since my kids were in bed as I was contemplating this as I put away their toys and found myself looking at exactly what I needed. First I used a set of four wooden balls that were red, green, yellow and blue. With the help of my patient husband that just wanted to go to bed I took this video of the four wooden balls under the changing light.

I only had one set of the wooden balls which wouldn't work for eight lab groups and I really wanted my students to try it themselves. I was pleased with the results but found that I wanted the other two primary pigments, magenta and cyan. I found one or two Duplos pieces in magenta but since we purposely don't have many "girl" Duplos I didn't think I'd have enough. But after dumping my kids' entire Duplos collection out onto the floor I managed to find enough magenta and a surprise store of cyan! Although humorously heterogenous, each primary pigment and secondary pigment was represented for each of my lab groups.

At this point I was promising we would be able to go really soon ... just as soon as I made a second video using the Duplos pieces:

For the actual lab the next morning students either used their own phones after downloading the app or used one of a few Samsung tablets that I borrowed from another classroom and preloaded with the app. Each group was able to observe the reflected color from the Duplos and of course anything else they could get in front of the light. It ended up being simple to do, relatable and more importantly for any light experiment it worked like it was supposed to.

Color addition egg

I enjoy teaching color and light not just because its fun hands-on physics but because I get to blow my students' minds. There is a special pep in your step on days you get to mess with them and tell them their elementary school teachers lied to them. My color and light lecture days are almost as fun as Van de Graaff demo day when I shock them repeatedly; almost.

Students "oooh and ahhh" over color addition; they never believe that red and green make yellow until they see it and some of them not even then. I have a few favorite color addition demos: "Colored Shadows" from The Exploratorium Snackbook; a Mysterious Glowing Ball from Educational Innovations; and this year a color changing egg. I found this at a local toy store and bought it for my son for Easter. It cycles through colors and I ask my students how it is able to create six different colors. Most students come to realize that there are only three LEDs in the egg; sometimes only one is on and sometimes two.

Since my daughter broke the first one we bought (she wanted to play with her brother's toy—she replaced it with coins from her piggy bank) I plan to take it apart so I can show my students the inner LED lights without the translucent white egg exterior. At less than $10 from a variety of sources (Amazon, etc.) it is a cheap and easy demonstration of color addition. Below is a video I took of it cycling through colors although it is better to see it in person.


Thursday, May 28, 2015

99.96% Black

A black purer than Ivory soap.

The substance, which is made out of carbon nanotubes and grows on aluminum foil, appears almost like a black hole because, in a way, it acts similarly to our eyes. Black holes produce such a large gravitational pull that light cannot escape it. Vantablack, on the other hand, absorbs so much light, roughly 99.96 percent, that it appears just as dark as a black hole. Even though the two objects are very different, they both confuse our eyes, which are not used to such an utter absence of light.

Click over to the article to see an image. Black can be a difficult subject for photographers.
This Material is So Black That Your Eyes Can't Fully Understand It

What else is black of late on the Internet?

Strindberg's need.

This Norah Jones track.

Monday, May 25, 2015

Colleague and Friend: Alec Hodgins

Point of Personal Privilege.

Alec Hodgins taught French at Rio Americano High School from 1988 to 2014. For virtually all of that time, he and I were either next-door classroom neighbors or across the small courtyard neighbors. In October, 2014, he went out on medical leave. A few weeks ago, he succumbed to depression. Those of us who knew him and loved him were devastated.

The comment I sherec with friends was, "Alec Hodgins was a unique soul whose creativity and diligence made him a pillar of Rio Americano High School. He was passionate about teaching French and playful in doing so. He inspired students. Deeply and permanently. In ways most teachers never will. The school is significantly diminished without his enthusiasm and energy."

Among other things, he was the motivation that energized my 15'x30' mural of Pink Floyd's Dark Side of the Moon outside my classroom.

I assembled a montage to convey the Alec Hodgins I got to know over the course of the 26 years I worked with him. It was included at a celebration of life commemoration we held after school last week.

Since the, a few more images were found. A slightly modified version of the presentation is shown below. It's neither brief nor comprehensive.

Alec Hodgins - Wish You Were Here

High school cultures are nothing if not ephemeral. If you went into a profession hoping to leave a legacy, you would have made a mistake in choosing high school instruction.

Physical manifestations of Alec will remain with our adjacent murals. He also instigated a scheme to develop Rio decals (window stickers) to help promote our Blue Ribbon school in the face of districtwide declining enrollment coincident with The Great Recession. He made a nice set of wooden return trays (for graded student work) and mini shelves so I could display the framed awards bestowed upon me and my students: The Wall of Ego.

More importantly, Alec's energy and empathy live on within those of us who valued his many admirable qualities.

If you need a moment at the end of the year

The NOVA episode devoted to the work of James "The Amazing" Randi makes a nice coda to any science course.

In the end, skepticism and critical thinking are important elements we hope we instilled during the year and will remain with our students long after the formula for kinetic energy has faded.

The full video is on YouTube here:
NOVA: James Randi's Secrets of the Psychics

An accompanying question sheet to help keep everyone engaged can be found here:
Video Questions for James Randi's Secrets of the Psychics.

More skepticism in the classroom lessons and links can be accessed from my Skepticism in the Classroom page.

Sunday, May 03, 2015

Kinetic Karnival links updated

It seems MySpace (yes, it still exists) changed all the URLs to their extant content. I'd snark, but kicking MySpace at this point just seems merciless and unfair.

Jearl Walker's excellent Kinetic Karnival videos are warehoused there, so all the links I had to his page and videos went bad.

The original post highlighting his videos and my curriculum was this:
Jearl Walker's Kinetic Kanival

Down the rabbit hole: Well, the links to my question sheets were equally outdated. So I've updated them. The linked PDFs are not always the most current, but should be fully-functional and correct.

Happily, I've updated the links, so this post is once again operational, as is the link in the right margin of this blog.

If you see that something's gone awry, please let me know. I'll do my best to get things repaired ASAP.

Monday, April 20, 2015

Disassemble, Yes!

As a child of the ’80s, I saw Short Circuit more times than I can count. To this day whenever I take something apart I hear the terrified Number 5 yelling, "Disassemble?! No!!" as he realizes what it would mean for him. But I still take things apart, because it is fun.

There have been many things I've collected (okay, maybe call it hoarded) over the years for use in my classroom. Some I have specific and immediate uses for .... some not so much. I still have part of the framing from a holiday light lawn sculpture of a snowman that I just know will be perfect for something, someday.

I finally got the time this year to disassemble an old toaster, hair dryer and space heater. I reference these appliances when I teach electricity as a practical example of the conversion of electric energy to thermal energy. By the time we get to that, students have often had personal experience with that conversion when they leave their circuits on too long and touch hot resistors.

Even though we've talked about the dissipation of heat from electrical circuits I don't think my students believed me until they saw all those coils of wire. It was a simple thing to take them apart (they weren't working anyway) but many of my students were just in awe of seeing the inside of something. Little do they know they get to do it next week.

Now that our current electricity unit has come and gone we have moved on to electromagnetism. I have my students make a speaker out of paper using a paper template I made (pdf or google doc), a doughnut magnet and a coil of magnetic wire. Its a simple build based on Modesto Tamez's activity from the Exploratorium, but the students love it every year. It can be expanded by asking students to improve the design, increase the volume or efficiency. I've also seen a headphone project follow this for which students have to make their own working headphones based on this speaker design. (NGSS Science & Engineering Practice right there!)

This year I'm adding a "Dissecting Headphones" lab to my unit. Thanks to RAFT I scored a gross of cheap ear bud headphones several years ago that I've been holding on to (hoarding again). Each pair of students will get a set of headphones so that they each get to dissect one ear bud. The instructions go step by step for these particular headphones and lead students all the way to the small magnet and coil. I've done it with high school aged students before and despite building the paper speaker only a few minutes before, they are shocked—shocked—that their ear buds work the same way. They use classroom scissors and a straight pin; they can use wire cutters too, but they are not required.

Suddenly they all start making connections. "This is how a microphone works, too!" and "That's why my headphones attract paperclips!" are heard all over the room. And it's magical.

The lab my students will do this week includes both the "Make A Speaker" and "Dissecting Headphones" labs in one file available as a pdf or google doc.

Thursday, April 16, 2015

ExploratoRio 2015 time lapse videos

We set up ExploratRio 2015 on Tuesday, April 14. That process looked like this.

ExploratoRio 2015 Setup

The following day we opened our doors to Rio physics students and local elementary school students. It looked like this.

ExploratoRio 2015 Day

Sunday, April 05, 2015

Canvas to Keynote conversion update

It began in October, 2012. Full story here.

At the outset, it looked like this.

In June, 2013, it looked like this.

Last year (April 2014), it looked like this.

Now (April 2015) it looks like this.

Progress. As sure as it is slow.

Sometimes demos go wrong—that doesn't make demos wrong

If you're hip enough to have tuned into this blog, you've probably seen the viral video of the cinder-block smash demo gone wrong. I'm not linking to it directly, because it's not any fun to watch. Of course, in this modern era, you can find versions of this incident from multiple angles.

I have mixed feelings about this demo and have never done it, myself. But I think Greg Schwanbeck makes a powerful argument against the knee-jerk reaction that will likely follow.

Please Don't Ban My … Physics Demos From Schools

And despite the date, this was no April Fool's joke.

Paly teacher burned in science experiment accident

Details are sketchy, so I'm not sure what conclusions can be drawn. No matter how often we've done some of these demos, it's imperative to remember the risk involved.

We wish speedy and full recoveries for both injured teachers.

And, OK; I'll give you a bed of nails blooper—direct from my talented and enthusiastic colleague, The Skeptical Teacher Matt Lowry. (Things get real at about 5:25.) He has recovered!

Tuesday, March 31, 2015

Van de Graaff Ping Pong

As played with a bundle of silk thread, as you do.

This gem comes to The Blog of Phyz from Inderkum's Jessica Downing, an upbeat, resourceful teacher at the most amazing high school in America.

It's a nice sequence of polarization, charging, repulsion, and discharging—rinse and repeat. It's like a puppy playing fetch.

This video below is slow-motion. This link will take you to the normal-speed version.

Van de Graaff Demo

Quantum locking

I guess I missed this one the first time around. Better late than never. I've seen magnetic levitation, but it didn't look like this.

Quantum Levitation

Uploaded on Oct 16, 2011
Video courtesy of the Association of Science-Technology Centers (ASTC), representing the science center and museum field worldwide. To learn more, visit Follow us on Twitter: @ScienceCenters.

Acoustic extinguisher

Low frequency sound douses a flame. I haven't seen a good explanation. In NGSSpeak, I'd say what we have here is engineering without a full scientific explanation. The explanation that, "it separates the oxygen from the fuel" is not working for me. Moving so much air that the temperature of the reactants is reduced below the combustion temperature seems more plausible.

Here's the article from Sputnik International

Pump Up the Bass to Douse a Blaze: Mason Students' Invention Fights Fires

Sunday, March 22, 2015

Electrophorus Engineering

One of the scariest parts of the Next Generation Science Standards (NGSS) are the Science & Engineering Practices. An easy way to slowly align your curriculum to NGSS is to modify a current demo, lesson or lab so that it is aligned with one of the Science & Engineering Practices. In a (brief) nutshell the Science & Engineering Practices are a skill set students should have in order to explore science phenomenon and engineer solutions to problems or fullfill a human need. Bozeman Science has a nice set of videos on the eight practices. The first one on Asking Questions & Defining Problems is helpful in understanding what NGSS considers the difference between Science & Engineering.

In the past I've created an electrophorus from a styrofoam cup and aluminum pie pan and used it to light a small neon bulb as part of my electrostatics lecture. Among The Exploratorium's many "snacks" is one called Charge and Carry that explains the traditional demonstration. Usually a styrofoam sheet is rubbed vigorously with a cloth to separate charge through friction. The electrophorus is set on the styrofoam and the charges in the aluminum pan polarize; by then touching the top of the aluminum pan you charge it by induction. If you pick it up by the insulating handle, touch one lead of a neon bulb to the aluminum while holding the other you can light a small neon bulb. You form a complete path of conducting material to the ground allowing charges to flow.

This year I did not show my students the electrophorus but asked students to experiment with different materials to explore the best way to light the neon bulb. Specifically students were working on the sixth practice "Constructing Explanations and Designing Solutions." Students had access to the following: plastic cups, plastic plates, paper cups, paper plates, styrofoam cups, styrofoam plates, aluminum plates, aluminum cups (made from rolled aluminum foil).

Students were given this image to understand the arrangement of their materials and instructions on how to charge and ground the electrophorus. Students were told to try different designs to light the neon bulb; each time they changed materials they were to record their results and try something else.

All groups eventually realized they had to use an aluminum plate to conduct the charge to the neon bulb. Most groups used a  styrofoam cup as the handle although some experimented with multiple stacked paper cups and reported a longer and brighter light from the neon bulb. Some groups tried rubbing the aluminum pan directly, skipping the styrofoam sheet, and reported even brighter lights.

After they optimize their design students were asked to write a conclusion paragraph: 
In an age appropriate paragraph explain (1) how the bulb can be lit this way and (2) justify your design choices and how well it worked. Be sure to discuss each of your designs and how their results influences later designs.  

As you might expect, results varied. Some groups really dove into it, referencing their book, asking me clarifying questions and constructed thorough explanations of what they were seeing. From others I could tell that students did not understand how the charge was initially separated, why a conductor was used for one part and an insulator for the other or how the static charge lit the bulb. By discussing their results the next day most students were able to correct their misconceptions. In the end I think they ended up with a much better understanding about the electrophorus and begin to see how current works than if I had just done it as a demo. 

Did it take longer? Yes. Was it worth it? Yes!

Electrophorus Build It Activity (PDF) (Google Doc)