Getting started with LEGO Robotics - the book and the real thing.

This week I got a special early holiday present in my mailbox from my friend Mark Gura. Mark had invited me a couple years ago to be part of a book for helping teachers new to the field of LEGO robotics get started with their students. We had a great conversation one evening after school over the phone during which we discussed the educational goldmine that building with LEGO is for students.

Mark did this with a number of people with a range of LEGO robotics experiences, wrote up our conversations, and then combined them with a set of resources that could be immediately useful to novices in the book.

The book, Getting Started with LEGO Robotics, is published by the International Society for Technology Education. If you, or anyone you know, is just getting started with this exciting field, you will find some great stuff in here to help you work with students and get organized.

It was a particularly perfect time for the book to arrive because we have a new group of students at my school getting started themselves with building and programming using the NXT. My colleague Doug Brunner teaches fifth graders across the hall. He volunteered (or more realistically, his students volunteered him) to take on coaching a group of students in the FIRST LEGO League program for the first time. After building the field for this year's challenge, today the fifth graders actually got their hands on the robots and programming software. I had the robots built from the middle school exploratory class available so the students could immediately start with some programming tasks.

We started with my fall-back activity for the first time using the software - program the robot to drive across the length of the table and stop before falling over the edge. The students were into it from the start.  I stepped back to take pictures and Doug took over directing the rest of the two hours. He is a natural - he came up with a number of really great challenges of increasing difficulty and wasn't afraid to sit down with students to figure out how the software worked. By the end of the session, the students were programming their robots to grab, push, and navigate around obstacles by dead reckoning. It was probably the most impressively productive single session I've ever seen.

It's always interesting to see how different people manage groups of students and LEGO. Some want to structure things within tight guidelines and teach step by step how to do everything. Others do a mini lesson on how to do one piece of the challenge, and then send the students off to figure out the rest. Some show by example that it's perfectly fine to get something wrong in the process of solving a challenge by working alongside students. It was impressive to see Doug think on his feet and create opportunities for his students to work at different paces but all feel accomplished by the end of the day. It is also really unique to have to tell a bunch of students  at 5:15 PM on a Friday to go home from school, and yet this has now been the norm in the classroom for a couple straight weeks.

Having robotics in my teaching load means that I am thinking about these ideas interspersed among planning activities for my regular content classes. There's no reason why the philosophies between them can't be the same, aside from the very substantial fact that you don't have to tell students how to play with LEGO but you do often have to tell them how to play with mathematics or physics concepts. It's easy for these robotics students to fail at a challenge twenty times and keep trying because they are having fun figuring it out. The holy grail of education is how to pose other content and challenge problems in the right way so it is equally compelling and motivating.

Note that I am not saying making content relevant to the real world. One of my favorite education bloggers, Jason Buell, has already made this point about why teaching for "preparation for the real world" as a reason to learn in the classroom is a flawed concept to many students that have a better idea than we do about their reality. I never tell people asking about the benefits of robotics that students are learning to make a robot push a LEGO brick across a table now because later on they will build bigger robots that push a real brick across the floor. Instead I cite the fact that seeing how engaged students are solving these problems is the strongest level engagement I have ever seen. The skills they develop in the process are applicable to any subject. The self esteem (and humility) they develop by comparing their solutions to others is incredible.

This sort of learning needs to be going on in every classroom. I used to believe that students need to learn the simple stuff before they are even exposed to the complex. I used to think that the skills come first, then learning the applications. Then I realized how incongruous this was with my robotics experiences and with the success stories I've had working with students.

Since this realization, I've been working to figure out how to bridge the gap. I am really appreciative that in my current teaching home, I am supported in my efforts to experiment by my my administrators. My students thankfully indulge my attempts to do things differently. I appreciate that while they don't always enthusiastically endorse my methods, they are willing to try.

Rubrics & skill standards - a rollercoaster case study.

  • I gave a quiz not long ago with the following question adapted from the homework:

The value of 5 points for the problem came from the following rubric I had in my head while grading it:

  • +1 point for a correct free body diagram
  • +1 for writing the sum of forces in the y-direction and setting it equal to may
  • +2 for recognizing that gravity was the only force acting at the minimum speed
  • +1 for the correct final answer with units

Since learning to grade Regents exams back in New York, I have always needed to have some sort of rubric like this to grade anything. Taking off  random quantities of points without being able to consistently justify a reason for a 1 vs. 2 point deduction just doesn't seem fair or helpful in the long run for students trying to learn how to solve problems.

As I move ever more closely toward implementing a standards based grading system, using a clearly defined rubric in this way makes even more sense since, ideally, questions like this allow me to test student progress relative to standards. Each check-mark on this rubric is really a binary statement about a student relative to the following standards related questions:

  • Does the student know how to properly draw a free body diagram for a given problem?
  • Can a student properly apply Newton's 2nd law algebraically to solve for unknown quantities?
  • Can a student recognize conditions for minimum or maximum speeds for an object traveling in a circle?
  • Does a student provide answers to the question that are numerically consistent with the rest of the problem and including units?

It makes it easy to have the conversation with the student about what he/she does or does not understand about a problem. It becomes less of a conversation about 'not getting the problem' and more about not knowing how to draw a free body diagram in a particular situation.

The other thing I realize about doing things this way is that it changes the actual process of students taking quizzes when they are able to retake. Normally during a quiz, I answer no questions at all - it is supposed to be time for a student to answer a question completely on their own to give them a test-like situation. In the context of a formative assessment situation though, I can see how this philosophy can change. Today I had a student that had done the first two parts correctly but was stuck.


Him: I don't know how to find the normal force. There's not enough information.


Me: All the information you need is on the paper. [Clearly this was before I flip-flopped a bit.]


Him: I can't figure it out.

I decided, with this rubric in my head, that if I was really using this question to assess the student on these five things, that I could give the student what was missing, and still assess on the remaining 3 points. After telling the student about the normal force being zero, the student proceeded to finish the rest of the problem correctly. The student therefore received a score of 3/5 on this question. That seems to be a good representation about what the student knew in this particular case.

Why this seems slippery and slopey:

  • In the long term, he doesn't get this sort of help. On a real test in college, he isn't getting this help. Am I hurting him in the long run by doing this now?
  • Other students don't need this help. To what extent am I lowering my standards by giving him information that others don't need to ask for?
  • I always talk about the real problem of students not truly seeing material on their own until the test. This is why there are so many students that say they get it during homework, but not during the test - in reality, these students usually have friends, the teacher, example problems, recently going over the concept in class on their side in the case of 'getting it' when they worked on homework.

Why this seems warm and fuzzy, and most importantly, a good idea in the battle to helping students learn:

  • Since the quizzes are formative assessments anyway, it's a chance to see where he needs help. This quiz question gave me that information and I know what sort of thing we need to go over. He doesn't need help with FBDs. He needs help knowing what happens in situations where an object is on the verge of leaving uniform circular motion. This is not a summative assessment, and there is still time for him to learn how to do problems like this on his own.
  • This is a perfect example of how a student can learn from his/her mistakes.  It's also a perfect example of how targeted feedback helps a student improve.
  • For a student stressed about assessments anyway (as many tend to be) this is an example of how we might work to change that view. Assessments can be additional sources of feedback if they are carefully and deliberately designed. If we are to ever change attitudes about getting points, showing students how assessments are designed to help them learn instead of being a one-shot deal is a really important part of this process.

To be clear, my students are given one-shot tests at the end of units. It's how I test retention and the ability to apply the individual skills when everything is on the table, which I think is a distinctly different animal than the small scale skills quizzes I give and that students can retake. I think those are important because I want students to be able to both apply the skills I give them and decide which skills are necessary for solving a particular problem.

That said, it seems like a move in the right direction to have tried this today. It is yet one more way to start a conversation with students to help them understand rather than to get them points. The more I think about it, the more I feel that this is how learning feels when you are an adult. You try things, get feedback and refine your understanding of the problem, and then use that information to improve. There's no reason learning has to be different for our students.

Geogebra for Triangle Congruence Postulates

It has been busy-ville in gealgerobophysicsulus-town, so I have barely had time to catch my breath over the last few days of music performances, school events, and preparations for the end of the semester.

My efforts over the  past couple days in Geometry have focused on getting in a bit of understanding of congruent triangles. We have used some Geogebra sketches I designed to have them build a triangle with specific requirements. With some feedback from some Twitter folks (thanks a_mcsquared!) and students after doing the activities, I've got these the way I want them.

Constructing a 7-8-9 triangle: Download here. (For discovering SSS)

Constructing a 3-4-45 degree triangle: Download here. (For discovering SAS)

Looking for an ASA postulate. Download here. (Clearly for ASA explorations.) - This one I made a quick change before class to making it so that the initial coordinates of the base of the triangle are randomized when loading the sketch. This almost guarantees that every student will have a differently oriented triangle. This makes for GREAT conversations in class. Here are three of the ones students created this afternoon:

I'm doing a lot of thinking about making these sorts of activities clearly driven by simple, short instructions. This is particularly in light of a few of the students in my class with limited English proficiency. Creating these simple activities is also a lot more fun than just asking students to draw them by hand, guess, or just listen to me tell them the postulates and theorems. Having a room full of different examples of clearly congruent triangles calls upon the social aspect of the classroom. Today they completed the activity and showed each other their triangles and had good interactions about why they knew they had to be congruent.

Last year I had them construct the triangles themselves, but the power of the end message was weakened by the written steps I included in the activity. Giving them clear instructions made the final product, a slew of congruent (or at least approximately in the case of 7-8-9) triangles a nice "coincidence" to lead to generalizing the idea.

Testing expected values using Geogebra

I was intrigued last night looking at Dan Meyer's blog post about the power of video to clearly define a problem in a way that a static image does not. I loved the simple idea that his video provoked in me - when does one switch from betting on blue vs. purple? This gets at the idea of expected value in a really nice and elegant way. When the discussion turned to interactivity, Geogebra was the clear choice.

I created this simple sketch (downloadable here)as a demonstration that this could easily be turned into an interactive task with some cool opportunities for collecting data from classes. I found myself explaining the task in a slightly different way to the first couple students I showed this to, so I decided to just show Dan's video to everyone and take my own variable out of the experiment. After doing this with the Algebra 2 (10th grade) group, I did it again later with Geometry (9th) and a Calculus student that happened to be around before lunch.

The results were staggering.

Each colored point represents a single student's choice for when they would no longer choose blue. Why they chose these was initially beyond me. The general ability level of these groups is pretty strong. After a while of thinking and chatting with students, I realized the following:

  • Since the math level of the groups were fairly strong, there had to be something about the way the question was posed that was throwing them off. I got it, but something was off for them.
  • The questions the students were asking were all about winning or losing. For example, if they chose purple, but the spinner landed on blue, what would happen? The assumption they had in their heads was that they would either get $200 or nothing. Of course they would choose to wait until there was a better than 50:50 chance before switching to purple. The part about maximizing the winnings wasn't what they understood from the task.
  • When I modified the language in the sketch to say when do you 'choose' purple instead of 'bet' on the $200  between the Algebra 2 group and the Geometry group, there wasn't a significant change in the results. They still tended to choose percentages that were close to the 50:50 range.

Dan made this suggestion:

I made an updated sketch that allowed students to do just that, available here in my Geogebra repository. It lets the user choose the moment for switching, simulates 500 spins, and shows the amount earned if the person stuck to either color. I tried it out on an unsuspecting student that stayed after school for some help, one of the ones that had done the task earlier.

Over the course of working with the sketch, the thing he started looking for was not when the best point to switch was, but when the switch point resulted in no difference in the amount of money earned in the long run by spinning 500 times. This, after all, was why when both winning amounts were $100, there was no difference in choosing blue or purple. This is the idea of expected value - when are the two expected values equal? When posed this way, the student was quickly able to make a fairly good guess, even when I changed the amount of the winnings for each color using the sketch.

I'm thinking of doing this again as a quick quiz with colleagues tomorrow to see what the difference is between adults and the students given the same choice. The thing is, probably because I am a math teacher, I knew exactly what Dan was getting at when I watched the video myself - this is why I was so jazzed by the problem. I saw this as an expected value problem though.

The students had no such biases - in fact, they had more realistic ones that reflect their life experiences. This is the challenge we all face designing learning activities for the classroom. We can try our best to come up with engaging, interesting activities (and engagement was not the issue - they were into the idea) but we never know exactly how they will respond. That's part of the excitement of the job, no?

From projectile motion to orbits using Geogebra

I was inspired last night while watching the launch of the Mars Science Laboratory that instead of doing banked curve problems (which are cool, but take a considerable investment of algebra to get into) we would move on to investigating gravity.

The thing that took me a long time to wrap my head around when I first studied physics in high school was how a projectile really could end up orbiting the Earth. The famous Newton drawing of the cannon with successively higher launch velocities made sense. I just couldn't picture what the transition looked like. Parabolas and circles (and ellipses for that matter) are fundamentally different shapes, and at the time the fact that they were all conic sections was too abstract of a concept for me. Eventually I just accepted that if you shoot a projectile fast enough tangentially to the surface of the Earth, it would never land, but I wanted to see it.

Fast forward to this afternoon and my old friend Geogebra. There had to be a way to give my physics students a chance to play with this and perhaps discover the concept of orbits without my telling them about it first.

You can download the sketch I put together here.

The images below are the sorts of things I am hoping my students will figure out tomorrow. From projectile motion:

...to the idea that it is still projectile motion when viewed along with the curvature of the planet:

Continuing to adjust the values yields interesting results that suggest the possibility of how an object might orbit the Earth.


If you open the file, you can look at the spreadsheet view to see how this was put together. This uses Newton's Law of Gravitation and Euler's method to calculate the trajectory.You can also change values of the variable deltat to predict movement of the projectile over longer time intervals. There is no meaning to the values of m, v0, or height - thankfully the laws of nature don't care about units.

As is always the case, feel free to use and adjust this, as well as make it better. My only request - let me know what you do with it!

Giving badges that matter.

The social aspect of being in a classroom is what makes it such a unique learning environment. It isn't just a place where students can practice and develop their skills, because they can do that outside of the classroom using a variety of resources. In the classroom, a student can struggle with a problem and then ask a neighbor. A student can get nudged in the right direction by a peer or an adult that cares about their progress and learning.

If students can learn everything we expect them to learn during class time by staring at a screen, then our expectations probably aren't what they should be. Our classrooms should be places in which ideas are generated, evaluated, compared, and applied. I'm not saying that this environment shouldn't be used to develop skills. I just mean that doing so all the time doesn't make the most of the fact that our students are social most of the time they are not in our classrooms. Denying the power of that tendency is missing an opportunity to engage students where they are.

I am always looking for ways to justify why my class is better than a screen. Based on a lot of discussion out there about the pros and cons of Khan academy, I tried an experiment today with my geometry class to call upon the social nature of my students for the purposes of improving the learning and conversations going on in class. As I have mentioned before, it can be a struggle sometimes to get my geometry students  to interact with each other as a group during class, so I am doing some new things with them and am evaluating what works and what doesn't.

The concept of badges as a meaningless token is often cited as a criticism of the Khan academy system. It may show progress in reaching a certain skill level, it might be meaningless. How might this concept be used in the context of a classroom filled with living, breathing students? Given that I want to place value on interactions between students that are focused on learning content, how might the concept be applied to a class?

I gave the students an assignment for homework at the end of the last class to choose five problems that tested a range of the ideas that we have explored during the unit. Most students (though not all) came to class with this assignment completed. Here was the idea:

  • Share your five problems with another student. Have that student complete your five problems. If that student completes the problems correctly  and to your satisfaction, give them your personal 'badge' on their paper. This badge can be your initials, a symbol, anything that is unique to you.
  • Collect as many people's badges as you can. Try to have a meaningful conversation with each person whose problems you complete that is focused on the math content.
  • If someone gives a really good explanation for something you previously didn't understand, you can give them your badge this way too.

It was really interesting to see how they responded. The most obvious change was the sudden increase in conversations in the room. No, they were not all on topic, but most of them were about the math. There were a lot of audible 'aha' moments. Some of the more shy students reached out to other students more than they normally do. Some students put themselves in the position of teaching others how to solve problems.

In chatting with a couple of the students after class, they seemed in agreement that it was a good way to spend a review day. It certainly was a lot less work for me than they usually are. Some did admit that there were some instances of just having a conversation and doing problems quickly to get a badge, but again, the vast majority were not this way. At least in the context of trying to increase the social interactions between students, it was a success. For the purpose of helping students learn math from each other, it was at least better than having everyone work in parallel and hope that students would help each other when they needed it.

It is clear that if you want to use social interactions to help drive learning in the classroom, the room, the lesson, and the activities must be deliberately designed to encourage this learning. It can happen by accident, and we can force students to do it, but to truly have it happen organically, the activity must have a social component that is not contrived and makes sense being there.

The Khan academy videos may work for helping students that aren't learning content skills in the classroom. They may help dabblers that want to pick up a new skill or learn about a topic for the first time. Our students do have social time outside of class, and if learning from a screen is the way that a particular student can focus on learning content they are expected to learn, maybe that makes sense for learning that particular content. In a class of twenty to thirty other people, being social may be a more compelling choice to a student than learning to solve systems of equations is.

If we want to teach students to learn to work together, evaluate opinions and ideas, clearly communicate their thinking, then this needs to be how we spend our time in the classroom. There must be time given for students to apply and develop these skills. Using Khan Academy may raise test scores, but with social interaction not emphasized or integrated into its operation, it ultimately may result in student growth that is as valuable and fleeting as the test scores themselves. I think in the context of those that may call KA a revolution in education, we need to ask ourselves whether that resulting growth is worth the missed opportunity for real, meaningful learning.

A smattering of updates - the good with the bad.

I want to record a few things about the last couple of days of class here - cool stuff, some successes, some not as good, but all useful in terms of moving forward.

Geometry:

I have been working incredibly hard to get this class talking about their work. I have stood on chairs. I've given pep talks, and gotten merely nods of agreement from students, but there is this amazing resistance to sharing their work or answering questions when it is a teacher-centric moment. There are a couple students that are very willing to present, but I almost think that their willingness overshadows many others who need to get feedback from peers but don't know how to go about it. What do I do?

We turn it into a workshop. If a student is done, great. I grab the notebook and throw it under the document camera, and we talk about it. (In my opinion, the number one reason to have a document camera in the classroom, aside from demonstrating lab procedures in science, is to make it easy and quick for students get feedback from many people at once. Want to make this even better and less confrontational? Throw up student work and use Today's Meet to collect comments from everyone.

The most crucial thing that seems to loosen everyone up for this conversation is that we start out with a compliment. Not "you got the right answer". Usually I tolerate a couple "the handwriting is really neat" and "I like that you can draw a straight line" comments before I say let's have some comments that focus on the mathematics here. I also give effusive and public thanks to the person whose work is up there (often not fully with their permission, but this is because I am trying to break them of the habit of only wanting to share work that is perfect.) This praise often includes how Student X (who may be not on task but is refocused by being called out) is appreciative that he/she is seeing how a peer was thinking, whether it was incorrect or not. I also noticed that after starting to do this, all students are now doing a better job of writing out their work rather than saying "I'll do it right on the test, right now I just want to get a quick answer."

Algebra 2

We had a few students absent yesterday (which, based on our class size, knocks out a significant portion of the group) so I decided to bite the bullet and do some Python programming with them. We used the Introduction to Python activity made by Google. We are a 1:1 Mac school, and I had everyone install the Python 3 package for OS 10.6 and above. This worked well in the activities up through exercise 8. After this, students were then supposed to write programs using a new window in IDLE. I did not do my research well enough, unfortunately, as I read shortly afterward that IDLE is a bit unstable on Macs due to issues with the GUI module. At this point, however, we were at the end of the period, so it wasn't the end of the world. I will be able to do more with them now that they have at least seen it.

How would I gauge the student response? Much less resistance than I thought. They seemed to really enjoy figuring out what they were doing, especially with the % operator. That took a long time. Then one student asked if the word was 'remainder' in English, and the rest slapped their heads as they simultaneously figured it out. Everyone enjoyed the change of pace.

For homework, in addition to doing some review problems for the unit exam this week, I had them look at the programs here at the class wiki page.

Physics

I had great success giving students immediate feedback on the physics test they took last week by giving them the solutions to look at before handing it in. I had them write feedback for themselves in colored pencils to distinguish their feedback from their original writing. In most cases, students caught their own mistakes and saw the errors in their reasoning right away. I liked many of the notes that students left for themselves.

This was after reading about Frank Noschese's experience doing this with his students after a quiz. I realize that this is something powerful that should be done during the learning cycle rather than with a summative assessment - but it also satisfied a lot of their needs to know when they left how they did. Even getting a test back a couple days later, the sense of urgency is lost. I had them walking out of the room talking about the physics rather than talking about how great it was not to be taking a test anymore.

Today we started figuring out circular motion. We played broom ball in the hallway with a simple task - get good at making the medicine ball go around in a circle using only the broom as the source of force.

We then came in and tried to figure out what was going on. I took pictures of all of their diagrams showing velocity and the applied force to the ball.

It was really interesting to see how they talked to each other about their diagrams. I think they were pretty close to reality too, particularly since the 4 kilogram medicine ball really didn't have enough momentum to make it very far (even on a smooth marble floor) without needing a bit of a tangential force to keep its speed constant. They were pretty much agreed on the fact that velocity was tangent and net force was at least pointed into the circle. To what extent it was pointed in, there wasn't a consensus. So Weinberg thinks he's all smart, and throws up the Geogebra sketch he put together for this very purpose:

All I did was put together the same diagram that is generally in textbooks for deriving the characteristics of centripetal acceleration. We weren't going to go through the steps - I just wanted them to see a quick little demo of how as point C was brought closer to B, that the change in velocity approached the radial direction. Just to see it. Suddenly the students were all messed up. Direction of change of velocity? Why is there a direction for change in velocity? We eventually settled on doing some vector diagrams to show why this is, but it certainly took me down a notch. If these students had trouble with this diagram, what were the students who I showed this diagram and did the full derivation in previous years thinking?

Patience and trust - I appreciate that they didn't jump out the windows to escape the madness.

_______________________________________________________

All in all, some good things happening in the math tower. Definitely enjoying the experimentation and movement AWAY from lecturing and using the I do, we do, you do model, but there are going to be days when you try something and it bombs. Pick up the pieces, remind the students you appreciate their patience, and be ready to try again the next day.

Testing physics models using videos & Tracker

I've gotten really jealous reading about how some really great teachers have stepped up and used programming as learning tools in their classes. John Burk's work on using vPython to do computational modeling with his students is a great way to put together a virtual lab for students to test their theories and understand the balanced force model. I also like Shawn Cornally's progression of tasks using programming in Calculus to ultimately enable his students to really understand concepts and algorithms once they get the basic mechanics.

I've been looking for ways to integrate simple programming tasks into my Algebra 2 class, and I think I'm sold on Python. Many of my students run Chrome on their laptops, and the Python Shell app is easily installed on their computers through the app store. It would be easy enough to ask them to enter code I post on the wiki and then modify it as a challenge at the end of beginning of class.. It's not a formal programming course at all, but the only way I really got interested in programming was when I was using it to do something with a clear application. I'm just learning Python now myself, so I'm going to need a bit more work on my own before I'll feel comfortable troubleshooting student programs. I want to do it, but I also need some more time to figure out exactly how I want to do it.

In short, I am not ready to make programming more than just a snack in my classes so far. I have, however, been a Tracker fan for a really long time since I first saw it being used in a lab at the NASA Glenn Research Center ten years ago. Back then, it was a simple program that allowed you to import a video, click frame by frame on the location of objects, and export a table of the position values together with numerically differentiated velocity and acceleration. The built-in features have grown considerably since then, but numerical differentiation being what it is, it's really hard to get excellent velocity or acceleration data from position data. I had my students create their own investigations a month ago and was quite pleased with how the students ran with it and made it their own. They came to this same conclusion though - noisy data does not a happy physics student make.

I wanted to take the virtual laboratory concept of John's vPython work (such as the activities described here) for my students, but not have to invest the time in developing my students' Python ability because, as I mentioned, I barely qualify myself as a Python novice. My students spent a fair amount of time with Tracker on the previous assignment and were comfortable with the interface. It was at this point that I really decided to look into one of the most powerful capabilities of the current version of Tracker: the dynamic particle model.

My students have been working with Newton's laws for the past month. After discovering the power of the dynamic model in Tracker, I thought about whether it could be something that would make sense to introduce earlier in the development of forces, but I now don't think it makes sense to do so. It does nothing for the notion of balanced forces. Additionally, some level of intuition about how a net force affects an object is important for adjusting a model to fit observations. I'm not saying you couldn't design an inquiry lab that would develop these ideas, but I think hands-on and actual "let me feel the physics happening in front of me" style investigation is important in developing the models - this is the whole point of modeling instruction. Once students have developed their own model for how unbalanced forces work, then handing them this powerful tool to apply their understanding might be more meaningful.

The idea behind using the dynamic particle model in Tracker is this: any object being analyzed in video can be reduced to analyzing the movement of a particle in response to forces. The free body diagram is the fundamental tool used to analyze these forces and relate them to Newton's laws. The dynamic particle model is just a mathematical way to combine the forces acting on the particle with Newton's second law. Numerical integration of acceleration then produces velocity and positions of the particle as functions of time. Tracker superimposes these calculated positions of the particle onto the video frames so the model and reality can be compared.

This is such a powerful way for students to see if their understanding of the physics of a situation is correct. Instead of asking students to check order of magnitude or ask about the vague question "is it reasonable", you instead ask them whether the model stops in the same point in the video as the object being modeled. Today, I actually didn't even need to ask this question - the students knew not only that they had to change something, but they figured out which aspect of the model (initial velocity or force magnitude) they needed to change.

It's actually a pretty interesting  progression of things to do and discuss with students.

  • Draw a system schema for the objects shown in the video.
  • Identify the object(s) that you want to model from the video. Draw a free body diagram.
  • Decide which forces from the diagram you CAN model. Forces you know are constant (even if you don't know the magnitude) are easy to model. If there are other forces, you don't have to say "ignore them" arbitrarily as the teacher because you know they aren't important. Instead, you encourage students start with a simple model and adjust the parameters to match the video.
  • If the model cannot be made to match the video, no matter what the parameter values, then they understand why the model might need to be adjusted.  If the simple model is a close enough match, the discussion is over. This way we can stop having our students say "my data is wrong because..." and instead have them really think about whether the fault is with the data collection or with the model they have constructed!
  • Repeat this process of comparing and adjusting the model to match the observations until the two agree within a reasonable amount.

Isn't the habit of comparing our mental models to reality the sort of thing we want our students to develop and possess long after they have left our gradebook?

It's so exciting to be able to hand students this new tool, give them a quick demo on how to make it work, and then set them off to model what they observe. The feedback is immediate. There's some frustration, but it's the kind of frustration that builds intuition for other situations. I was glad to be there to witness so we could troubleshoot together rather than over-plan and structure the activity too much.

Here is the lab I gave my students: Tracker Lab - Construction of Numerical models If you are interested in an editable version, let me know. I have also posted the other files at the wiki page. Feel free to use anything if you want to use it with your students.

I am curious about the falling tissue video and what students find - I purposely did not do that part myself. Took a lot of will-power to not even try. How often do we ask students to answer questions we don't know the answer to? Aren't those the most interesting ones?

I promise I won't break down and analyze it myself. I've got some Python to learn.

Presenting the MVT In Calculus w/ Geogebra...tech as a game changer.

During our warm-up activity today, we looked at a function and identified critical points, relative, and absolute extrema for this function:

It was kind of neat talking about this and the extreme value theorem from last time. Since the domain is not defined over a closed interval, the EVT doesn't guarantee the existence of an absolute maximum or minimum value. The students seemed to really get the idea this year that this function specifically has no absolute maximum over the domain because it is an open interval - last year there was a lot of confused faces on this idea. There were a couple really insightful comments about whether there would be an open interval domain over which the function did have an absolute maximum, even though the hypothesis wasn't satisfied. The theorem just tells you whether or not you are guaranteed to find one, not that there isn't one at all. Really good stuff, and I'm proud of the way everyone was chiming in to talk about what they understood.

The most important thing was that this led perfectly into introducing the idea of an existence theorem. This idea is different from other theorems (especially in comparison to geometry) that students have learned because the information it gives you is not as specific as "alternate interior angles are congruent" or "the remainder of polynomial P(x) upon division by (x - c) is P(c)". All it does is tells you whether you can find what the theorem says is there. I didn't plan on having this discussion today, but it was perfect for then introducing the mean value theorem, and I will definitely repeat it in the future.

I then gave my students this geogebra applet to play with today.

Download link here.

The students understood pretty quickly what they had to do, and didn't seem to have a hard time. It was kind of interesting to watch them rediscover the concept of forming a tangent line using two points, as that concept has been a bit overshadowed by other things as we looked at derivative rules before the test they took last week. Some students moved P and Q so that they were tangent, and then adjusted the domain using C and D to find a domain over which the tangent line and line AB were parallel.

From this, I showed them what the slope of line AB represented (average rate of change over the interval) and came up with the right side of the MVT. We then talked about what the slope of the tangent line they identified represented - a couple immediately referenced the derivative of the function. What is the relationship between parallel lines? What would make it so that you couldn't find this value? Ideas of continuity and differentiability jumped out. There it was: the entire mean value theorem.

Last year I presented the students with the MVT, and then we drew graphs to represent what it was saying. They kind of got it, but it wasn't a sticky idea. I was doing all the developing. This approach today started with something visual that they were doing, that they could understand intuitively, and then that intuition was applied to develop an abstract concept out of that understanding.

I continued doing what I had done last year - answering some multiple choice questions about the MVT (See here for today's handout) analytically, and I immediately lost a couple students. So I showed them how to throw the new function into Geogebra and adjust the domain to match the problem. They could then solve the problems graphically - they immediately located the points to be able to answer the questions.

The group is a mix of AP and non-AP exam bound students. I will introduce them all to the analytic ways of identifying these points, and we did some of it today. It was really nice that the moment things got a bit too abstract, I could push students to identify how the question being asked was the same as the idea of the MVT, and they were then able to solve it.

Without the technology, these students would have been done for the rest of the period. Those that could handle the algebra, would. Those that couldn't would spend the rest of the period feeling like they were in over their heads. Introducing how to use the technology to really understand what was being said by the abstract theorem enabled many more students to get in on the game. That made me feel all warm and fuzzy inside. The rest of the class focused on definitions of increasing functions using the derivative, something that was made incredibly easy by referring back to the activity at the beginning of the period.

We'll see how well they remember the ideas moving forward, but it felt great knowing that, at least for today's lesson, everyone in the room had a way into the game.

Having conversations about and through homework

I've been collecting homework and checking individual problems this year. I grade it on completion, though if students tell me directly that they had trouble with a question before class (and it is obvious it isn't a case of not being able to do ANY of it because they waited until the last minute to try) I don't mind if they leave some things blank. I did this in the beginning since I had heard there were students that tried to skip out on doing homework if it wasn't checked. We do occasionally go over assigned problems during class, but I tend not to unless students are really perplexed by something.

I have lots of opinions on homework and its value. Some can use the extra practice and review of ideas developed in class. Some need to use homework time to make the material their own. In some cases, it gives students a chance to develop a skill, but in those cases I insist that students have a reliable resource nearby that they know how to use (textbook, Wolfram Alpha, Geogebra) to check their work. I don't think it is necessary to assign it just to "build character" or discipline. I read Alfie Kohn's The Homework Myth, and while I did find myself disagreeing with some aspects of his arguments, it did make me think about why I assign it and what it is really good for. I do not assign busy work, nor do I assign 1 - 89 - each problem I assign is deliberately chosen.
Among the many ways I try to assess my students, I admit that homework doesn't actually tell me that much about the skill level of a student. Why do I do it then?

My reason for assessing homework is for one selfish reason, and I make no secret of it with my students:

The more work I see from students relating to a concept, the better I get at developing that concept with students.

I would love to say that I know every mistake students are going to make. I know many of them. If I can proactively create activities that catch these misconceptions before they even start (and even better, get students talking about them) then the richness of our work together increases astronomically. You might ask why I can't get this during conversation or circulation with students during the class period. I always do get some insight this way. The difference is that I can have a conversation with the student at that point about their thinking because he or she is in the room with me. I can push them in the right direction in that situation if the understanding is off. The key is that most of my students are alone when they do their work, or at least, have only online contact with their classmates. In that situation, I can really see what students do when they are faced with a written challenge. The more I see this work, the better I get.

I am not worried about students copying - if they do it, it always sticks out like a sore thumb. Maybe they just aren't good at copying. Either way, I don't have any cases of students that say 'I could do it in the homework, but can't do it when it comes to quizzes or tests.' Since I can see clearly when the students can/can't do it in the homework, I can immediately address the issue during the next class.

The other thing I have started doing is changing the type of feedback I give students on homework. I still fall into the habit of marking things that are wrong with an 'x' when I am not careful. I now try to make all feedback a question or statement, as if I am starting a conversation with a student about their work through my comments, whether positive or negative:

  • Great explanation using definition here.
  • Does x = 7 check in the original equation? (This rather than marking an x when a solution is clearly wrong.)
  • (pointing out two correct steps and then third with an error) - mistake is in here somewhere.
  • You can call "angle CPK"  "angle P" here.
  • Good use of quotient rule - can you use power rule and get the same answer?

The students that get papers back with ink on them don't necessarily have wrong answers - they just have more I can chat with them about on paper. The more I can get the students to understand that the homework is NOT about being right or wrong, but about the quality of their mathematical thinking, I think we are all better off.

This does take time, but it is so valuable to me, and I think the students not only benefit from the feedback, but appreciate the effort on my part. I don't check every problem, just key ones that I know might cause trouble. If a student has everything right on the questions I am checking, it's a chance to give feedback on one of the others. If there's nothing to say because the paper is perfect (which is rare), I can praise the student for both their clear written solutions, hard work, and attention to detail.

I decided at the beginning of this year to look at more student work, and checking homework in this way is letting me do this. I am lucky to have prep time in the morning, and I have committed to using morning time for looking at student work almost exclusively. I have had to force myself to do this on many mornings because it's so easy to use the time for other things. Some of my best ideas and modifications to lessons come after seeing ten students make the same mistake - it feels good to custom fit my lessons to the group of students I have in front of me.

In the end, it's just one more way the students benefit from having a real teacher working with them instead of a computer. Every mark I make on the paper is another chance to connect with my students and conversation that can help make them better thinkers and learners. I don't think I really need to justify my presence in the classroom, but it feels good to say that this is one of the reasons it's good I'm there.