Fortnite Fisiks

A while ago I tweeted about how a couple students were working on Capstone projects that involved Fortnite, and there was a substantial (by my standards) interest in the details, so I’m here to share what they came up with!

First, for some background on what the Capstone process looks like in my class, head over to this post from last year. Even though I said I would like to change some stuff, I didn’t very much this year… I need a better system for making sure I actually incorporate the changes I think of, plus my wife had our third boy in April so like… I’m giving myself a mulligan on this one. If I get it together and improve the project for next year I’ll let you know.

So basically, what happened was this: two students who had a below-average level of engagement during the regular school year jumped at the chance to choose whatever topic of inquiry they would like for their capstone project. These particular kids are huge fans of Fortnite, the improbably popular Battle Royale game. When we were discussing how previous students had analyzed video games, I brought up that Fortnite actually has some real potential as a basis for Physics inquiry. It has a pretty good spectator-replay mode where you can view any action in the game with a fixed camera, so you can do video analysis on different actions in game (provided you can execute those actions without, um, getting executed). When they realized that they could look at Fortnite, it was off to the races.

One student does a lot of YouTubing about video games and was aware that another vlogger he follows had put out the fan theory that maybe Fortnite happens on the planet Venus. One of the main pieces of evidence was that the acceleration due to gravity is weaker in Fortnite than on Earth, explaining why the characters can jump so high, but my student wondered whether that was really the case because the vlogger proposing this theory hadn’t actually taken data or done the calculation. So we talked about what kind of data he would need to find out whether they were right.

The second student was interested in analyzing an aspect of the game’s physics that contributes to the technical mechanics of winning it: “bullet drop”, which is the distance a bullet falls as it reaches its target. Players of this game who use the longest-range rifles need to get good at aiming above their targets to account for this feature, which is built in to balance the weapon type and keep it from being overpowered. We talked about what kinds of things you could calculate that had to do with bullet drop. This was a great back-and-forth because he was an expert on what information the game makes easily available to the player, and because he hadn’t been that engaged this year, he now had a lot of really good questions about what you could do with that information to figure out other information. We settled on using a measured shot distance and bullet drop to estimate average bullet speed.

In order to make the bullet drop calculation, this second student also needed to know the acceleration due to gravity on the mysterious Fortnite world. This was an awesome authentic overlap between the two students’ projects, which meant that they would be able to check their work by looking for agreement on this value (or potentially uncover interesting inconsistencies in the game’s physics).

The two students also had to solve the problem of determining the scale of the Fortnite world, and they each came up with different, interesting ways to measure and estimate distances. I’ll link their projects below so you can see what they did. (I advise skipping the 6 and a half minutes or so of the first student’s video – he spends a lot of time going over the other vlogger’s Venus theory and doesn’t get to the physics until after all of that. But the formal response to the other guy’s work was important to him and part of his motivation for working, so while I found it pretty uninteresting, I think he got value out of it – I still advised him in my feedback to reduce the length and intensity of this part of his video.)

I’ll just let you know ahead of time that neither student actually completed their calculations correctly. After I went through and fixed their math mistakes, I found that 1) the numbers that they calculated for gFortnite actually came pretty close to agreeing, and 2) the second student’s estimate for the bullet speed is not an inappropriate value for a real-life rifle. Both of which were pretty cool!

The “Is Fortnite on Venus” video:

The “Estimating Rifle Speed” slideshow:

Now since the students didn’t get the math right, was their work a waste of time? Heck no! These were two students who had a hard time finding something to “own” about the course for most of the year. As part of this project, they set their own goals and had an incredibly authentic experience of gathering data, trying to make sense of it, and comparing work with a colleague. I think the work they did mirrored, in some really important ways, the work that scientists did at the dawn of Newtonian science to determine the best way to measure motion in our real universe. Finding different ways to calculate the same value and taking their agreement as justification for the linked conceptual frameworks that support each one? I mean come on!

Ultimately, we had fun and got some real Physics done, but this was also a missed opportunity. We didn’t have time to close the assessment loop and get their issues corrected. My curriculum partner and I have found this is a pretty common problem with many of our capstone projects – students generate all these auxiliary problems as a result of the true freedom they’re granted in choosing a topic and format, and many times end up forgetting something important about the physics concepts in their final result. In the future we’re going to move the presentations up so that there’s time afterwards for them to incorporate feedback from peers and teachers. I also lament that we didn’t do this project earlier! Having piqued the interest of these two earlier in the year, could I have kept it going and had them bring more energy and interest to other areas of the curriculum?

So, what do you think? I will readily admit that these projects are pretty rough, but I think they actually kind of make the case that opening up the opportunity for students to do some independent research and setting their own goals, even in the sort of worst-case-scenario where they don’t get it totally right, is still a worthwhile experience.


What my students think of my class

We have a long weekend around President’s day so I’m trying to get back on the blog train. Some time ago I posted a midyear survey that I sent to my classes – admin asked us to do it as part of our midterm protocol this year. I’ve been teaching for 9 years and this is the first time I’ve actually done such a survey in the middle of the year rather than at the end, and it made me wish I had done so earlier! The student responses were really informative and immediately led to a few changes, and I think more are coming soon. If you don’t often poll your students on the features of your class, I hope reading my questions and responses will convince you it’s a good idea.

I was seeking feedback on three specific changes that I made to my classes this year. First, the homework logs. I incorporated a “choose-your-own-adventure” homework policy (a la Casey Rutherford) and wanted to ask for feedback on how that was working out for them. I was feeling pretty pleased with the program but I wanted to give students a chance to say how they really felt about it.

Second, I’ve continued to tweak my grading system. I’ve been working with a standards-based grading system mostly modeled after Kelly O’Shea for a few years, and I wanted to see how students were responding to the latest iteration.

Finally, I needed some honest feedback about the computational modeling portion of the curriculum. This has been the biggest adjustment this year and continued buy-in from the students is pretty key.

I also added some general questions at the beginning about the format of the course in general, and some of the responses there – to things I’ve been doing for years – actually surprised me more than any of the responses to the “new stuff”. That’s actually getting a separate post.

Below, I’ll provide some examples of student responses along with my thoughts and the changes I made. All the histograms are from two sections of Honors Physics. I had both sections take the survey on the same form so that I wouldn’t let my feelings about either section color my response to their answers.

HW Logs

(The scale was “complete waste of time” to “definitely improves my understanding”)

This is like an almost perfectly neutral response! Here’s some of the (overall) positive:

I like it because I like having the choice of what to do. It also forces me to review some of my notes from class which is helpful in retaining the information.

i’m not used to this system but i think it’s helpful

At first I did not but I am starting to enjoy it because it forces you to see if you understand the material or not

I like the system, gets us to do problems on our own

It is somewhat annoying to do every week but it certainly helps me to confirm my understand

Here are some more lukewarm to negative:

There are a lot of times when I don’t know what to do for homework and I wish we were assigned one packet we could do outside of class, but overall I think it pushes me to think and focus on what I need to improve in. Good preparation for self-guided learning in college.

I like that it forces me to practice my skills each week so I do not forget anything. However I often cannot find time to complete them because of sports or other projects, and other times forget about them until Thursday.

Worst part of the class easily. So time consuming and daunting. This system sounds good in theory but instead just serves as busy work.

Sometimes I feel like I do the problems over and over again and its a waste of time

Sometimes giving students too much power/freedom doesn’t work. Id prefer more rigidity

The students who have done a good job with their homework logs have done a REALLY good job this year! I have seen lots of explicit reflection on their own work and on class activities, and a lot of outside-of-class collaboration. Some students are clearly struggling to figure out how to use their time wisely. They feel like there are too many options and they don’t know how to get started. In response, I did two things right away: first, I shortened the weekly homework log from 2 hours to 1. I don’t want anybody feeling like they’re just “keeping busy”. (I know I could go all the way to not having a specified time limit, but I think having a benchmark helps people make practicing Physics a priority.) Second, I started making an effort to have specific parts of my packets available to students for HW log time. I’m trying to just point out more explicitly when students could start a problem set ahead of a class discussion, or finish some extra problems that we didn’t have time to get to in class. As a result, this week some students worked ahead on problems that they didn’t yet completely know how to solve and their problem-solving journals contained statements like “I need to talk to my group more about the direction of friction in problems like these when we whiteboard these tomorrow”. Kids setting their own short-term learning goals? I’ll take that as a win, even if not everyone’s doing it yet.

LO 1(scale was “This never happens” to “This happens all the time”)

LO 2(scale was “I am very confused” to “The feedback makes complete sense”)

Well, the skew of these histograms is promising, but I feel like as an instructor, you really want basically everybody to be 4’s and 5’s. Nearly half of my students are 3 or less on both of these. My conclusion is that we need to be talking about the learning objectives more. I’m making a concerted effort to increase the frequency of assessments as a result, and so we’ll be talking a lot more about what each objective means.

The comments show that despite not having any other class that works this way in their high school experience, my students are really enthusiastic about the general premise of SBG (that your grades reflect your state of understanding on specific objectives, and new grades replace your old ones instead of averaging).

I like it because on tests we are not afraid to go with what we think instead of being scared of the grade

I really like this system and I think it’s easier to improve with it in place

I honestly like this system just because physics problems are so multifaceted that if you screw up one little calculation at the beginning it can screw up the rest of your problem. To complete the rest of the problem correctly and not be penalized for a petty mistake is very encouraging.

I appreciate that my grades reflect my understanding instead of how correct I am because in other classes I often find I do not perform wel in tests but felt I understood the material (and just make some careless mistakes)

And here’s some cooler feedback, with one very gutsy kid who admits they think I grade too easy?

The learning objectives are a little confusing because I don’t know what exactly is expected of me to improve on. For example what part of the problem needs to be fixed

I like this system because it encoruages me to improve my scores instead of focusing how I don’t know it and merely movingly on. Sometimes I feel like the grade doesn’t represent what I actually know however (in an inflated way)

I do wish there was more flexibility in the available grades. My mom can look at my powerschool and interrogate me as to why I got a D- on something; it makes me want 7s and 9s just for added flexibility. I understand that it’s not meant to be a D-, but that’s what it’s interpreted as. Getting 6’s doesn’t motivate me to do better, it makes me feel hopeless in ever getting a 10.

I like it, but maybe 9’s should be an option! Just since I think it is very accurate, but can be bad if you don’t understand and get 5s or 6s

i like the feedback but i do not like how it is translated into grades. the grading system is restrictive in that you can only get certain numbers, which is not really realistic.

(You probably recognize the 5-6-8-10 system the kids reference in these comments, because it is yet another thing I cribbed from Kelly.) It’s funny how the last three are really not complaints about MY SYSTEM, they’re more complaints about the requirement that feedback be converted into an accountability score, and the fact that we constantly judge kids based on their grades. I’m not so sure what I can do about this within my own system, but I’m considering implementing a system where I display scores but wait to calculate the quarter grade until the midquarter, when there have been enough assessments for that calculation to be meaningful (right now I went with PowerSchool’s default setting of calculating everything right away).

Having already taken some steps to make the learning objectives more understandable and more a part of the classroom dialogue, I’m also a little concerned about the kid who thinks that they’re getting good ratings but not understanding. Wish this one wasn’t anonymous so I could ask for more details! Maybe having this issue raised will help me notice when other students feel this way.

Here’s the last set of questions – about the computational modeling aspect of my course this year…

Pyret 1

Pyret 2

Pyret 3

Womp womp. To be honest, these were some of the least surprising responses for me, because this is the first year that I’m teaching programming as part of a physics class, and I could tell during many of the lessons that I was whiffing pretty hard. This is probably the single riskiest thing I’ve ever done as an educator, and the class didn’t totally fall apart nor did the kids completely stop doing it, so I’m going to count it as a win even though there were a lot of failures. I think my experiences with computational modeling in the high school classroom are going to be worth, like, a few of their own blog posts later on in the year, so stay tuned. Here are some heartening comments though, for any of you who are thinking of trying this stuff in your own room:

As time went on the correlation between what we were learning and the pyret activities became more evident.

I think my problem solving skill improve because pyret makes you apply what you learned in class to the computational modeling

I started this year fearing programming. I think I understand how everything is meant to connect and how literal and step-by-step it is.

As my abilities in pyret have grown, I have been able to conceptualize the motion needed to satisfy new problems. I don’t enjoy it, but I coexist peacefully. I feel like I have the tools to build onto my knowledge.

Like I said – a HANDFUL of kids had a positive response and that’s enough to keep me going until I can improve this part of my class in a future iteration.

So, I highly recommend asking your students specific questions about new stuff you try in your class, because their words can spur concrete changes. I usually only make changes to my major class structures in the fall when I’m feeling fresh, but the armpit of February is actually an excellent time to shake things up a little, and having kids tell you what they think provides motivation to do so. Plus, when I rolled out a few of these changes to my students, the immediate effect was that they were surprised and grateful that I was taking action in response to their words. That kind of give-and-take in the student-teacher dynamic does so much to help students feel like they have a voice.

You Can’t Win if You Don’t Play

So I tried something totally new to me this fall. I always start the year with a series of classes on the nature of science and the importance of the scientific community in generating scientific knowledge and understanding (it’s basically this but shorter). This year I decided to make a lesson explicitly addressing issues of equity and bias in the science community.

My hope was that I could lead the class to name the problem of racial and gender inequity and bias in science, and that I could let students know that this was a class where those topics aren’t off limits and where we are interested in ensuring equal access and stature in the community for everyone. My fears were that students wouldn’t understand why we were talking about this stuff in a science class, or that some of them would be used to detecting and dismissing any talk in a social justice vein and wouldn’t engage. (I care more about making the young women and minoritized kids in my class feel welcome than I do about shaking up a rich white kid’s day, but I also was fearing that if I alienate them then I won’t make any progress with them.)

The lesson plan was to introduce gender equity and bias in the scientific community as a relevant struggle facing the scientific community through a look at the infamous Google memo controversy of this summer. I didn’t want students to read the whole memo so I picked a couple editorials that addressed it. My idea was for half the class to read each one, summarize the arguments, and hopefully get some ideas out on the table. Articles here and here.

Here are the questions I had them answer and discuss after reading:

  1. Summarize the argument made in your assigned article.
  2. What feelings did you have while reading this article? Anger, sadness, pride, excitement, embarrassment? Pick one and try to explain specifically what part of the article made you feel this way.
  3. How does the author address the question of whether there is inequity or bias in STEM fields?
  4. What questions do you have about the factual statements made in your article and the evidence used to support it? Pick a specific factual statement made and say whether you believe it. If so, why? If not, what additional information would help you evaluate this claim?

What I was hoping was that the groups would see that the two articles were actually addressing completely different questions. The WIRED article sought to provide evidence that gender bias in science is a real, documented phenomenon. The National Review article sought to muddy the waters on whether Damore’s claims of innate biological gender differences had scientific merit. I was hoping that if they could identify this difference I could point out that it actually doesn’t matter what the scientific consensus ends up being on gender differences, because bias clearly does exist and it’s a thing we can actually take action on. Over the weekend they were assigned further reflection questions to think about what we can do in our own class to combat bias, and to take an IAT if they choose.

I had students answer the questions individually and then discuss them in small groups. Everybody was engaged during this part of the class but some of them were having reactions that I didn’t expect. First of all, a lot of students were pretty convinced by the National Review article. This feeling turned out to be validated by a lot of their written responses. They had a hard time teasing apart the different claims being made and understanding which ones were overreaching. I ended up regretting that I provided this “counterpoint” – turns out propaganda works. I was afraid this might happen, but I had to see it to understand why. More surprisingly to me, many students found the WIRED article to be “too opinionated” and so they didn’t trust the citations. I pointed out that there were 7 or 8 links to scientific journal publications, but I could tell some kids felt like I was forcing this opinion on them – mostly 11th grade boys, but a few girls could also be heard saying, as they were discussing this article, they don’t think that women have to work harder to achieve the same recognition as men. I was floored. I thought this article was perfect because it presents concrete evidence that bias exists AND it addresses the fact that it can be hard to accept this evidence for some people. But as a person who’s been on the internet more than zero times, I guess I should know by now that just reading articles doesn’t really convince anybody of anything.

In the class discussion portion, I ended up feeling both like I wished I had more time and that people didn’t talk enough. I didn’t come up with a way to incorporate whiteboards so there wasn’t student work to reference right there. I could have done something where people wrote stuff on poster paper or something. Missed opportunity. I lamely wrapped up by just making the point for them that there’s a lot of evidence that bias does exist and that we can do something about it, and referring them to the information on the IAT that I included at the end of the assignment.

I had the chance to talk with a couple students directly after one of the classes, and they had a couple interesting insights. First of all they were both sympathetic – they knew I wasn’t completely pleased with the way this went, but they gave me credit for trying something different. One student, a 12th grade boy, said he thought that there was way too much writing – we should have gotten straight to the discussion. Very fair point! Ultimately I think I misunderstood what kind of experience is going to do the heavy lifting in changing people’s opinions – and it’s not going to be through rationally considering the articles. It’s going to be through hearing how people feel. It’s not quite the same as a physics model where it’s really important that kids do logical analysis first, and then compare their findings in a group. It’s not as straightforward to shepherd the group to the “right” answer.

The other student stayed to talk to me for longer. She’s a 12th grader who happens to be the president of the Women’s Empowerment club (I did not know this before the lesson). She said she thought that the responses of the students ranged from really appreciative (mostly the senior girls) to indifferent at worse (mostly the junior boys). She said that she thinks that overall in the school culture there is an understanding that girls care more about social justice and the wider world, and boys tend to mock that sort of thing. I thought that was interesting and it wasn’t a trend I had picked up on – obviously I’ve met counterexamples to both sides but I wonder how many students would agree with her on that. It was really interesting for me to lift the lid on this aspect of the school’s cultural life and realize how I never even scratch the surface on most days – and how much my kids actually desperately need MORE experience talking about these things, more tools for coming together over these issues, not less.

Coming back on Monday, some kids (a little more than half, and seemingly mostly girls – drat) reported that they took an IAT, but I didn’t want to discuss it too much more at this point. Despite the fact that I clearly pushed it with Friday’s lesson, the students seemed to be able to give me the benefit of the doubt and dive into the customary Constant Velocity Buggy Lab with gusto. I have a fun computational modeling piece of this activity this year, so let’s see how much political capital I really have left here 😀

So: I can comfortably call the lesson itself a failure, I think. But of course I’m going to fail better next time, and here are some takeaways that I’m going to bring into play next time this comes up. (If you think of any more things I should have taken away I would love it if you would share in the comments.)

  1. I decided to focus on gender more than race because we have very few nonwhite students in our classes, and I wanted to shoot for maximum relevance to our classroom scientific community. But, this concession turned out not to make it that much easier to teach, and I think that students in our school really need to work on sensitivity to all of the groups that have historically been excluded from science. So I will choose materials next time that highlight both race and gender.
  2. I need to loosen up on the reins a little bit. The activity I designed did not really trust the students; it was really tightly controlled. I was worried that people wouldn’t draw the same conclusion I did from reading the two materials, and I let that influence my planning. After a little reflection I realized that this felt very familiar and it was like when I first started doing student-led discussions and I was afraid to let them drive. My goal has to be more modest: I may not convert any new feminists, but if I can show them that scientists can reasonably engage in this kind of discussion, and provide the first exposure to some of these ideas, and show that we can talk about these things without fighting, I will have done some work.
  3. I will be able to loosen up the reins, and students will be able to undertake this conversation more safely, if we wait until we know each other a little better. My classes end up building a really functional discussion community where people aren’t afraid to take risks and really do get to know each other a little bit. I could be using this to our advantage. I think in the future I would like to seed some ideas in the beginning of the year, then make time around the end of quarter 1 to discuss them in more detail. Danger: will I “run out of time” and avoid bringing it up at all?
  4. Of course right after I attempted this little experiment, I saw this in The Physics Teacher:

They take a lot more time than I had planned, and they also do a great job of situating the discussion about equity in a larger discussion of “what is physics”. The IAT is a more central piece – they do a better job of convincing students that this discussion is necessary. Next time I go for this I’m going to take a page from their book.


One reason that I believe in inquiry so strongly is that I have never been able to take advice – I always try things on my own, mess up, and then look back and think “oh… THAT’S what they were warning me about”. I decided to jump in with both feet and give this lesson a shot knowing that it could completely tank, because I think I owe it to my kids. I ask them to step out of their comfort zone and try new things every single day. If I can’t do the same for them, what kind of a teacher am I?

Capstone 2017

I’ve always been a true believer in the power of inquiry. You only really learn the answer to a question when you have figured it out for yourself in your own head, and you only have the resilience to follow through and do that when you have some authentic reason for asking that question in the first place. But most of the time, even the most inquiring of inquiry teachers twist inquiry to our specific curriculum goals, and heavily assist students in their choice of question, method, and analysis. We have to! There simply isn’t time to let students wander down whatever garden path catches their interest for the entire year.

Luckily, I had a couple advantages this year that allowed me to go all in on inquiry at the end of the year.

1) I have been blessed to join a new Physics team this year that I feel really complements my strengths and weaknesses. We’ve learned a lot from each other this year. I pretty much lifted my curriculum partner’s entire Capstone procedure for my own, and as soon as I can finally get her to join the Internet of Physics Teachers I’ll be sure to link this post to her.

2) Internships. Seniors all left, so I had between 5 and 10 students remaining in each of my classes. This allowed me to micromanage the process for each of them a little bit and make sure that anyone who got stuck could be promptly… inspired.

3) An admin team that are willing to lengthen the leash a little. For the first time this year, the Physics department was allowed to completely replace the final exam with a capstone project. It was no longer just a filler activity for the final week of school, it was now 10% of each student’s grade for the year!

So as long as everyone is aware that I can’t really take personal credit for any of this, today I’d like to share the broad outlines of the procedure students followed, some anecdotal results (both good and not so great), and my own thoughts on what I might change next time around.

The Steps

Step 1. Brainstorm Areas of Interest. Students were given a list of “starter” ideas to get them thinking, and then spent most of one period coming up with ideas. In that first session, they were required 5 minutes of “acoustic” brainstorming (no internet or technology) followed by an additional 10 minutes in which they could look some stuff up, and they had to determine at least 5 potential areas of interest for a project. Finally each class met as a group and shared their ideas. We discussed pros and cons of the favorites and the class helped each person determine which area of research was likely to be most fruitful.

Step 2. Determine Product and Audience. Students were next tasked with creating an “elevator pitch” describing their product. In creating this pitch, students needed to come up with a thing they were going to make or do, and who cares?, i.e. who is the audience for this work? Examples of what they came up with this year:

an experiment on refraction for the other students in this class

a lesson on Newton’s Third Law of Motion for middle school students

an video analysis of the gravity in Super Mario Galaxy for publication on YouTube

In retrospect, I didn’t lean hard enough on students to come up with an interesting audience for their work. I still think their projects came out ok, but most of them really just “wanted” to make a presentation for the other students in the class. I think this is probably because that’s just what they’re used to, so while I really like the idea of this authentic audience piece I personally need more planning to make it happen.

Step 3. Develop Timeline and Request Resources. In this step students created a schedule for their work and tried to itemize any materials they would need to buy or borrow from our equipment room, and come up with any assistance they would need from me or other adults in the building (e.g. one kid built a pinhole camera so she needed the photography teacher’s darkroom, another kid was interested in mirrors and lenses so she needed me to get out the optics materials from the prep room). This was also where I went around and negotiated with them about the scope of their project. Most students at this point still thought they were going to “just do a powerpoint or something”. HAHAHAHAHA! I gently reminded them that there needed to be some PRODUCT of their inquiry – either a device they were building or an experiment they were conducting, or a calculation they were making and comparing to existing data.

Step 4. Execute Timeline and Check In. About halfway through this process students had to fill out a “checkpoint” form explaining what they had done already, what they still needed to do, and stating when exactly they were going to do it. We reviewed the schedule for the week to help them realize what their options were. This was an important step because many students needed to go shopping for materials and bring them to school, or have videos made so they could be analyzed, so it helped them to know that they really needed to get these preliminary steps done ASAP.

Step 5. Design Rubric and Final Conference. Students were involved in determining how they would be assessed. They were asked to describe what would make the difference between “exemplary” performance and simply “proficient”, and also to come up with the categories in which they would be rated. By modifying lines from an existing bank of rubrics that my colleague has been storing up for a few years, I was able to take this input from each student and create a custom rubric. Here’s an example.

The goals for the sculpture were agreed on by myself and the student based on his background reading. After each rubric was created I had a 5 minute check in with each student to discuss what I was thinking and modify it based on what seemed reasonable.

Presentations were given during the final exam block for each class. I didn’t worry about time limits – I wanted students to focus more on the WORK they were doing – the presentation was just to tell us about it.

So, How’d It Go?

On balance – great! I am not completely sure how I feel about the amount of coaching I provided to my students. Some kids took an idea and ran with it! For example, I had one student who was interested in doing a movie or video-game fact check. I reminded him about the video analysis we had done with iPads and Vernier earlier in the year and pointed him towards Tracker (our school has chromebooks which can’t run Tracker, but a couple kids have their own laptops, so they can). He picked Super Mario Galaxy and ran with it. I checked in with him for the checkpoint but hardly talked to him the entire time and he landed up with this. (I could also write an entire nother post probably on how he successfully uses rulesets for science “explainer videos” as a compositional structure, fulfilling the “authentic audience” requirement – but let’s not get too far into that.)

Another student had this idea that he was going to build a Newton’s Cradle. I tried to talk him out of this because, like, who seriously cares about a Newton’s Cradle? But he was really into it, so I said if he could use the Newton’s Cradle to explain something about conservation of momentum then that could be his project. And as predicted, it ended up pretty bad – building it was harder than he thought, because you have to get a really hard material and have it line up perfectly, and he didn’t really learn anything about momentum from doing it. (He also lost some class time due to a sports absence, and I probably could have done a better job about following up with him).

A third student really wanted to make a speaker. He looked up how to do it on the internet and at first I was like “man, this sucks, he’s just going to follow some steps”. He was very skeptical when he bought the magnets and wire that it would actually work, and sure enough, his first effort barely made a sound. But it DID make some sound! This was enough to pique his interest, and by the time he was done he had changed magnet shapes, replaced the bottom of a plastic party cup with packing tape for better vibration, created a smooth surface for the magnet to move against inside the coil, and worked out a way to fasten everything together so the speaker could be easily picked up by anyone. His presentation didn’t show a deep understanding of magnetic induction, but it did show that he had a better functional understanding of what’s necessary to turn an electrical signal into motion. So it’s not exactly the knowledge I would ideally like someone to walk away from this project with, but it’s 100% his, and that’s cool.

And still another student was interested in “something to do with light, I don’t know, mirrors and reflections and stuff”? I couldn’t really get her to narrow that idea down any more, so I got out the optics materials and asked her to design an experiment. I led her along in this maybe a little too much, I’m afraid – I set up a source and a lens and showed how you can locate the image on an index card. She thought that was pretty cool, so she messed around with it on her own a little and she was able to figure out pretty easily that it would make sense to move the location of the source and see how that affects the location of the image. She needed a little more help with fitting the data, and I was worried that maybe I was doing all the work for her. So I backed off and told her that she needed to do the background research on her own to figure out what model explained her data. I gave her two hints: thin lens equation and ray tracing. In her final presentation she had worked out the geometric proof of the thin lens equation and was able to use a ray diagram to explain how that 2-parabolic-mirror-with-each-focal-point-at-the-surface-of-the-other-mirror trick works. So I ended up being actually surprisingly pleased with how that one worked out. It ended up being a great deployment of the experimental design and physics learning skills we had worked on in every single unit this year. You can see her presentation in the link that I tweeted here.

I don’t know, do you think I helped too much?

Project Categories

Overall, the projects ended up falling into 4 major categories (and one weird outlier which delighted me but that I may not see again).

  1. Design a quantitative experiment, then do background research to interpret the results. (Kind of a do-your-own modeling unit in miniature.) This is what ended up happening when students were interested in a phenomenon that wasn’t really covered by any of the models we had already worked on this year.
  2. Build something (instrument, art object, functional device), then use it to teach a physics principle to the group.
  3. Choose an area of inquiry and construct a goalless analysis of that system. (This is what ended up happening when students were interested in a phenomenon that WAS pretty well covered by the models we worked on this year.)
  4. Do some research in an unfamiliar area of physics and then teach a lesson to the class. (Kids who wanted to do this had to include one demonstration, one strategy to actively engage the audience, and also had to complete self-reflection questions telling me how they think it went. Next time I’m going to make them also do a mini-assessment!)

I’m strongly considering providing these templates to students next year maybe AFTER they have already brainstormed their topics but before they have written their elevator pitch. It might help structure their inquiry. One thing I DON’T like about this is that I think it kind of cuts off the “authentic audience” angle a little bit, but maybe there’s some way to meld the two approaches.

Do you do a Capstone assignment in your Physics or other science or math class? Do you have any useful tips for free-range inquiry? Let me know in the comments!

How do you KNOW there are two kinds of electric charge?

My last post involved some self-criticism of the pacing I used this year, but this post is about something I feel like I pretty much nailed. I wanted to give a little more airtime to our treatment of the 2-charge model for electric interactions, because I was very satisfied with the path we found this year to justifying this idea. Many students come in with some background knowledge of electric charge, but just like Newton’s Laws, there are some things they have often been taught to say that just aren’t right, and other things that they’ve accepted without really thinking about them. (I mention this because I’ve heard some secondary teachers say that it’s not worth spending this much time introducing students to the basic ideas of positive and negative charge from an inquiry standpoint, because they “already know” about that stuff.) However, I think Introductory Electrostatics is a really important time to hammer home the nature of scientific understanding, because we take an area of inquiry that seems impossible to scientifically address – the invisible, submicroscopic structure of the matter around us – and give it a solid underpinning in logic and direct observation. This sequence has worked for me (roughly) with 9th graders but it takes more time to tie together all the pieces. This year I found that 11th and 12th graders seem to have more bandwidth for their working memory, and do a better job of connecting observations over multiple class periods and coming up with the conclusions before getting distracted. Again, I’m mostly just following the AMTA Modeling materials, but this is my personal spin on it. (1 day = 55 min class time)

We start with a basic observation of a balloon being rubbed with fur and then attracting other objects (I like to hang the balloon from the ceiling and rub it before anyone comes in the room, then start with my hand juuuuust barely close enough that the balloon begins to attract so it looks like I’m magic. You kind of have to be a kid to teach kids I guess.) I point out that we may think of “electricity” as a feature of modern life, but human awareness of this weird push and pull goes back thousands of years, to regular folks finding these strangely beautiful resinous-looking stones that can act on each other at a distance when rubbed with animal fur. We call this material amber today. So if you’re a shepherd, sitting bored out of your skull because you have nothing better to do than look at sheep all day and rub amber stones on your wool clothes and play with them, what might be your name for this force? “Amber-force?” Yep! But the Greek word for “amber” was “electrum”, so the interaction became known as “electricity”, the quality of behaving like electrum. What this little story is meant to do is to signal to students that we’re not about to read and memorize some esoteric definitions in a book – we’re just describing our observations and trying to form patterns, you know, like humans do?

We then move directly into Sticky Tape Electroscopes, a real classic from Arnold Arons that made its way into the official AMTA Modeling Materials on Electrostatics: basically, if you stick a piece of tape to the back of another piece of tape and then peel them apart, they get opposite electrostatic charges – a “top” and “bottom” tape. I give a worksheet where students first compare the tapes to each other, then a number of neutrally charged objects. We find that top tapes always repel other top tapes, but attract everything else, and bottom tapes always repel other bottom tapes, but attract everything else. In addition, a piece of paper and foil which do not interact with each other at all are still somehow able to attract both top and bottom tapes. At this point we define “charged” and “uncharged” behavior – an object is “charged” if it can both push and pull other objects, but “uncharged” objects can only pull “charged” ones and don’t interact with each other at all.  [Sidebar: It’s important to keep the discussion at this phase focused on categorizing the behavior rather than explaining it. That’s for Day 2.] So what rule summarizes all the behavior we observe? Many students “know” this result ahead of time and will dismissively toss off the rule “opposites attract”, but this initial idea doesn’t hold up for long: if a foil strip attracts both top and bottom tapes, is it “opposite” to both top and bottom? We finally settle on “like charges repel”.

With this rule in hand, I turn students loose to identify the charges on a rack of “mystery tapes”, which this year was, in order, a foil strip, an acetate strip, another foil strip, and an unmarked piece of magic tape, each of which I had given an electric charge or simply left alone (I use a mixture of materials to begin to seed the idea that any object at all can carry an unbalanced charge – having 2 conductors with different charges really helps in later lessons when they start to conflate the concepts of “conductor” and “charged”. The prompt is, “Identify whether each mystery strip is a top tape or a bottom tape.” We whiteboard our results. One group’s identifications, in order, were “top, bottom, bottom, top”, and another group’s were “top, bottom, top, top”. Though they had different answers, neither had made any mistakes in their data collection – only in their reasoning. When they compared methods, they realized that the first group tested each strip with a top tape ONLY, and the second group tested with a bottom tape ONLY. The effort taken by the students in a conversation like this to reconcile their conflicting interpretations drives home the utility of “like charges repel” as a working model for electrostatic interactions, and the fact that neutral objects attract BOTH top and bottom tapes.

As a final step for Day 1, I tell them that Ben Franklin also studied electricity – he called the kind of charge that develops on a glass rod rubbed with silk “positive”, and the other kind negative. Then I ask them how we could test which kind of charge our top and bottom tape have. We observe that the charged glass rod repels a top tape, and a plastic rod rubbed with fur repels a bottom tape, and from here on out we can use Franklin’s (+)/(-) system for labeling our tapes and charges. Then comes the kicker: what kind of charge is on a neutral-behaving object?

Students very quickly float 3 suggestions, all of which are flawed in some crucial way. I write all suggestions down as they come up and ask for criticisms and strengths for each one. The main ideas I try to get them to consider are that neutral objects have.

  • …a third kind of charge. Strength: explains behavior with (+) and (-) as attraction to “unlike” charge. Criticism: then why don’t neutral objects repel each other, as “like” charges?
  • …no charge at all. Strength: explains why neutral objects don’t interact with each other. Criticism: how are neutral objects able to pull on charged objects?
  • …a mixture of (+) and (-) charges. Strength: explains why both charges are attracted. Criticism: why is the attraction stronger than the repulsion?

Most classes manage to come up with all 3 ideas and objections on their own, and students pretty quickly take sides. And that’s where we end day 1 – undecided on the problem of neutral behavior. I think it’s really important to recognize that scientists do this sometimes.

Day 2 involves sketching charge distributions for an assortment of situations involving tapes and other objects. Pretty soon students realize that the mixture of charges works best to explain most phenomena, particularly “where do the charges come from” when preparing a set of sticky tapes (models 1 and 2 require (+) and (-) charge to appear from nowhere, but for model 3 the answer is “it was on the tapes already and we just “sorted” most of the (+) to the top tape and the (-) to the bottom tape). Finally I ask them to determine the charges and the forces each tape would feel in the following arrangement.

In the resulting discussion, students compare diagrams until they agree on the number, direction and relative amount of each force felt by each tape. Then I ask them to predict which way each tape would be pushed or pulled overall. This leads them to conclude that in this arrangement the top tape at left would be attracted to the arrangement of tapes at right. Usually at this point when I send them directly from this problem back to the question of how a neutral object can attract a top tape, somebody figures it out and explains it to the class. We name this arrangement of charges “polarized” and I ask some follow-up questions about “what if we approached with a bottom tape, and are the neutral objects always polarized or not” and by the end of this discussion, we are able to vote on which model from 1, 2, or 3 above seems most likely. Students are often very satisfied that they were able to answer definitively at the end of Day 2 the question that seemed so intractable at the end of Day 1, and we’re now ready to use our hard-won model to explain more complicated phenomena like induction and grounding.

I love this sequence because it provides evidence for why the 2-charge model exists, and it provides a framework for students to understand how scientists can come to have knowledge about things that we can never directly observe. Numerous students commented to me that they really felt like they were learning a lot during these two days, which I chalk up to their active participation in reasoning through what for them was a legitimate mystery: the “neutral”-behaving objects. I mean, think about all the fragments a kid may have encountered: “a bulb needs a positive and a negative to light”, “every negative needs a positive”, “protons, electrons, and neutrons”, “opposites attract”. To say nothing of the moments when a kid looks up at me after the Ben Franklin discussion and earnestly asks “which side of a magnet is positive?” (And you better believe I keep a straight face, bust out a magnet, and we test it together!) It’s only in very carefully posing and answering questions that arise from their own observations that they can finally put together a conceptual model for themselves. So that’s why I spent two days on “positives and negatives” and I’m not sorry!

How to teach CASTLE in 1 week

Pacing is my Achilles’ heel as an educator. Well, when it comes to pedagogical weaknesses I often feel like I’m ALL heel, but if I had to pick just one, pacing would be it. On a good day I tell myself it’s because of my deep-seated belief that you just can’t rush authentic learning. But anyway, I am always finding that when I reach the “end” of a unit I never “get as far” as I “would have liked”. But I was pretty satisfied with how our work in electrostatics and DC circuits went this year – the first time I’ve taught this material to 11th & 12th graders. (I did teach it to 9th graders for 3 years, so I have something to compare it to, but the pacing is radically different for this age group.) Below, I’ll reflect upon an outline of what I did and what I would do differently next time. Mostly, I followed Unit 01 of the AMTA E&M materials, and a somewhat mashed-up version of the first few units of CASTLE. (When I refer to a “day” I am talking about a 55 minute period.)

I’ll elaborate on some specifics of our execution in a later post, but people who are familiar with this curriculum might find just the pacing chart to be an interesting point of comparison.

  1. Intro to Electric Charge: it took me 2 days to do the Sticky Tape Electroscopes and discuss polarization, and I’m not sorry at all. We develop a 2-charge model for explaining electric attraction & repulsion, and thoroughly build a case for the charge distribution on a “neutral” object. (I got a little carried away as I was describing this and I will present my “storyline” for this initial encounter in a separate post – stay tuned!)
  2. Moving Charges & Grounding: I spent 1 day on constructing and problem-solving with the Electrophorus – drawing charge diagrams to explain charging and discharging. In retrospect, I think we could have been more efficient in drawing & discussing the charge diagrams and spent a little more time on talking about why “grounding” works. I think I need to add some specific worksheet questions to develop both why a moving charge would prefer to go to a neutral object, and why the “ground” never obtains a net charge.
  3. Model Deployment (2 days): we break out the Van de Graff generator! We have a very shocking 400 kV generator that makes for some very memorable moments. Human Chain is an indispensable activity for reinforcing conductors, insulators, and grounding. I did skip whiteboarding for these observations, and it was ok – because it was mostly a demonstration of what they already had learned from the electrophorus. We took time to draw the difference in the charge distribution on a polarized conductor vs. a polarized insulator. This felt a little contrived – in all but one class I had to “help” way too much to get them to come up with a model that explains the behavior – and also like it took too long. I think we could dispense with this point entirely. I then had everyone fill out the charge distribution diagrams for the pie pan worksheet – basically lots of different conduction, induction, grounding procedures that can be performed with the VDG and 2 other conducting objects. Then we tested the predictions. Again, I think I need to add some supplementary discussion questions about WHY the charge gets evenly shared between identical conductors when they’re put in contact (many students think the entire unbalanced charge will jump to the second conductor, returning the first one to neutral, and they have no explanation for why that doesn’t happen – they need a bridging question to help them get there.)
  4. Quiz (1 day) – this shouldn’t have taken this long, I should have given them a better time limit. We had 3 different deployment activities; it was my most active and most fun quiz of the year. I have to do more assessments like this (but I forget). Q1 – draw a charge distribution explaining why the balloon can stick to the wall after I rub it with fur. Q2 – observe this gold-leaf electroscope and draw charge distributions explaining why the leaves separate when it’s approached with a charge. (Honors classes also had to explain the NEW behavior after the electroscope is grounded in the presence of a charged object.) Q3 – given an electrophorus and a second conducting sphere on an insulated post, there are TWO distinct procedures each that will result in the placement of a (+) and a (-) charge on the second conductor. Find and illustrate any 2 methods & perform them on the materials in the class

I was pretty pleased with this sequence. Next we took up the quantitative side of electrostatics, which I had actually NEVER done before at all, so I could definitely improve on this:

  1. Coulomb’s Law Experiment (1 day) – after discovering that the video included with the Modeling materials actually gives a 1/r³ relationship, I ended up deciding to use an old apparatus we had on hand to make a similar video. We took data on the video as a class and then students analyzed it in groups. They were pretty excited to find the same relationship for electric force as gravitational force once I pointed out that they should be >.< This took a whole day because we had to diagram the experiment and justify using horizontal displacement of the hanging pith ball as a proxy for electric force before we could actually take the data.
  2. Coulomb’s Law practice (2 days) – this was kind of low engagement. I think I can punch up this worksheet a little more and do it in less time. I really like the use of a hydrogen atom to contrast the electric force and the gravitational force but my students were not really at home with this context, particularly at the Standard level. The problems tend to be pretty plug & chug at first and then rapidly get harder when you are dealing with the net electrostatic force due to more than one charge. I like that Vector Addition Diagrams make a roaring comeback after not having seen them during momentum and energy, but everybody groans when you have to bust out Law of Cosines (myself included TBH) since diagrams are rarely right angles. I think I need to emphasize the ratio reasoning more at the beginning, and the order of magnitude comparison between gravity and electricity, and leave the tough vector problems as enrichment for kids who are working ahead.
  3. Electric Field – so here’s where I really did my kids a disservice I think. I was running short on time and wanted to get to problems where you actually are using the electric field to make calculations (like a Millikan oil drop style problem), so I thought I would just do the pen-and-paper field mapping activity from the Modeling materials, skipping the “electric compass” activity. BIG MISTAKE! They quickly created the vector field showing the electric force on a test charge at different points in space, and then I had them calculate how the force at a particular point would change for simple multiples of the test charge, graph it, and discuss the meaning of the slope. I planned no discussion of field lines at all, thinking I’d help them draw a quick analogy between N/C and N/kg and we’d be on our merry way. But without field lines we had no way of talking about how an electric charge affects the space around the charge and things got weird. So I ended up quickly showing them how to draw field lines which felt terrible. In the future I would definitely start with some field mapping activities with many different charge distributions, predicting the field lines for a novel distribution, and then add on the quantitative part as a second layer. I’ll just have to take more time if I want students to actually understand what a field is!
  4. Test – a mixture of qualitative and quantitative problems on the electric force and field.

After electric fields, we switched gears and looked at circuits. I have taught CASTLE before but only to 9th graders in an extremely drawn out (but fun) process. This time I wanted to compress it down to approximately a week, and it almost worked, actually.

  1. The Closed Loop Model and Make it Light! – I kicked off the unit by handing students a bulb, a wire, and a battery. When they couldn’t do it, we proceeded to move quickly through CASTLE activities 1, 2, and 3: disconnecting a loop circuit at different points to observe that the bulbs always go out, and investigating different parts of the bulbs and sockets to determine that the closed conducting path must include the tip & threads of the bulb in order to light. After making these observations, they were able to very quickly figure out the “make it light” challenge. Then I showed them that one video of Harvard & MIT grads who couldn’t light a bulb 😀 This all very neatly fit in one class.
  2. Introducing the Capacitor – The next class began with the confusing observation (made as a class) that even though a capacitor breaks the continuous conducting path, the bulbs still light briefly, and not only that, the capacitor can then light the bulbs on its own. I then showed them how to use a compass to measure the direction of charge flow, also still as a class. I then sent them back into groups to measure the flow direction in the charging and discharging capacitor circuit. By the end of this day we were able to conclude that charge flow is still unidirectional and that it reverses in the discharging circuit. I added a piece where they predict which way charge will flow when the batteries are reversed during charging, and when the capacitor’s direction is changed between charging and discharging, and we test as a class, which was a good way to end this day.
  3. Other sources of moving charge – We moved maybe a little too quickly here. I gave them a sheet with lots of fun things to try with a hand-crank generator that led them to conclude that the role of the generator, the battery, and the capacitor is always simply to push and pull the charge that’s already present in the circuit. (Fave activity: have someone connect and disconnect the circuit as you steadily turn the crank of the generator – every student gasps in amazement that they can actually feel a greater resistance when the circuit is connected.) We revisited the question of where the charge comes from in the “bottom” plate of the capacitor in light of this information. Maybe it’s just that they had already studied electric charge that they didn’t seem as mystified that the charge is “already in the wires”, but I thought maybe it just hadn’t sunk in. At the end of this class I busted out “Capacitor Senior” and had them explain why the bulbs lit longer but not brighter during charging, and why the large capacitor could turn the genecon with more cranks.
  4. Why does charge move in a circuit? – things started to break down a little more here and this ended up being my last day before we had to move on to our capstone project, which if it goes well I’ll also write about here. I wanted to get to the idea of charge pressure, so I moved CASTLE unit 4 (charge pressure) up before the activities in unit 3 (resistance). This ended up being tricky because it’s hard to build up the idea of pressure without something to press against! So I don’t think I’d try this stunt in the future. I started this day with a puzzle: I showed the students 2 capacitors and charged the (+)-labeled plate of one of them. Then I “shuffled” them under the table and asked them to determine which capacitor had been charged, WITHOUT discharging it. They figured this out, and then we did the prediction and observation of charging a capacitor with multiple battery packs, after which we dramatized the pressure of the built-up charge by discharging a capacitor charged with ~110 V through a wire.(They love this of course.) Then we looked at dueling batteries, which wasn’t quite as impactful without being able to think about the resistance of the bulbs. I stand behind this pacing but I guess since I didn’t really have a chance to finish the arc I can’t totally judge how effective it was. If I had more time I would have taken the next day to diagram the capacitor charging process in terms of pressure, using the color-coding worksheets from CASTLE unit 4. From there I would have done 1 or 2 days on resistance and then an Ohm’s Law lab and some equivalent resistance problems. I think overall that would have been a pretty reasonable amount of time to spend on circuits that still contained a lot of inquiry.

Well, if anybody has any thoughts on this process I’d of course be thrilled to hear them! It’s been fun to end the year with electrical weirdness after nearly the entire rest of the year dedicated to mechanics.