Sunday, September 11, 2016

Absent Students: What to do...what to do?

I am a practitioner of the Modeling Methodology and have been for about 15 years. 

A colleague of mine sent an email the other day that asked me:

"I am wondering how you handle the logistics of students being absent and not having a textbook during modeling. How do they catch up?"

I feel that my reply is good enough to share.

Great question!

I get questions like this all the time from first time modeling workshop participants.
I don't think this is why you're asking but let me provide the scenario that I encounter.
There is an inherent supposition by teachers who are thinking of transitioning to a new methodology that "if they switch it should fix all of the problems in the classroom".
When I write it down it seems ridiculous.  But I get this a lot from participants.  Not in such an overt way but it manifests in the question, "If all of the learning happens in the classroom, what do you do with students that are absent?"
The short answer is, "The same thing you do now with students that are absent."
There is an assumption by traditional type teachers that kids can learn from textbooks, or notes/power point presentations posted on a teachers website, or Khan Academy videos.  
And often teachers who tell students who are absent to consult these resources feel like they are off the hook if they do these.  Here is an example:
Student - "I was absent yesterday; what did I miss?"
Teacher - "Get the notes from the 'notes binder', here is the worksheet and watch this video."
There are, as I see it, two problems with this.  The first is the idea that a student could really do any conceptual learning with these resources - in or out of the classroom!  It just can't happen.  They can barely even do any factual learning with these resources let alone really learn anything.  The second is the idea that it is hard for us to admit that if the student isn't there, they just can't learn.  We as teachers hold ourselves to a standard that says, "even if a student is absent, we should still be able to get them to learn what we want them to learn."  But is that really a reasonable expectation?
So when I say to participants do do "The same thing you do now with students that are absent."
What I really mean is, "Do nothing."
Sure, you can provide some notes that were taken (or they can get them from a friend) and you can give them some worksheets that were distributed - which are both reasonable and responsible.
But there is no substitute for being there.
But let's contrast some of the features of the modeling methodology with something more traditional.
In a traditional classroom, absent students are in much dire straights because often the teachers have  a schedule of topics to cover.  Like, on Monday we're "doing" constant velocity; on Wednesday we're doing constant acceleration.  They sprinkle some practice problems in on the in between days but there is very little cycling of the content and very very little checking for understanding.  If you missed it, too bad, we've moved on.
With the modeling methodology, we plan and implement the development and deployment of content over several class periods.  This allows students to develop their concepts and understandings at their own pace and we give them multiple opportunities to practice.  We're continually checking for individual and group understanding and making changes to our plan to accommodate.
So, when a student is absent, its fine because even if they missed a day they are going to have more opportunities to learn and practice.
Switching to the modeling methodology doesn't fix all of our problems,  but it does highlight some of the logistical short comings of teaching.  And it allows us to be honest with ourselves about what we can and can't do; about what is within and out of our control.

Friday, July 22, 2016

#unitrebel Why unit analysis is overrated and why cancelling units borders on criminal

The following is my opinion based on 20 years of teaching physics at various high school levels from AP C to a trig-based to an algebra-based to a collaboratively taught special education version.  

A couple of weeks ago, I was participating in a white board circle during a modeling workshop.  The white board at which we were looking contained a notation that showed something that like: (m)(kg)/(kg) = (m).
In 'student-mode' I was like, "what happened to the kgs?"
The answer came as, "then cancelled."
I then asked, "what do you mean 'they cancelled'?"
What followed was a 20 minute session of 4 or 5 know-it-alls trying to convince me that kg/kg = 1.
Now, to be honest, I was being a little bit obstinate.  But my ulterior motive was to ask the question to the group:

"Why do we spend so much time talking about units?"
"What does it even mean to 'cancel' units?
"Why do we let our students cancel units?"

In my experience working with students of all levels, units mean very little to them.  That is a hard truth given how much they mean to us -  trained physics teachers and physicists. However, units are for people who already understand units.  When you watch an expert problem solver read and interpret a physics problem, select an appropriate equation, plug in the numbers with the correct units, cancel and solve, it looks like a maestro conducting a symphony.  However, is that our students?

Introductory physics students struggle at each step of this process.  And to ask them / require them to include the units in the problem solving steps and it really does just get in the way.  We would love if it promoted better problem solving or if it helped them make more meaning of a problem.  That would be AWESOME!  And I bet for some students it probably does.  But the students who get the units are already good problem solvers and don't need the benefits we would like the units to provide?

So what do I do about things like Newtons, Joules and Amperes?
When a new topic get introduced, usually through some sort of physical experience, the question of measurement and units comes up as a question posed by the students.  With force it is easy because the spring scales they use are calibrated in Newtons.  I would rather a student know how 1 N worth of force feels like in his hand than what the base units are.

Joules are very tricky.  In fact, there not a great way for students go discover these units.  So guess what?  I don't really use them!  The students decide that the measurable energy is calculated as the area between the graph line and the horizontal axis on a Force vs. Displacement graph.  So the units of energy, as described by the students are Nm.  Does calling this a Joule give the students more of an understanding?  I don't really know.
Current is more like force in that the multi-meter they are using has units of A already so we just go with it.

If, then sometime down the road, the students want to know something like, "what exactly is a Newton/Joule/Ampere anyway?"  Then we can get down and dirty because they (hopefully) have the contextual knowledge and practice to answer the question for themselves.

We know that real learning comes through discovery and conversation.  So any discussion of units has to have those two components.  If I am just the disseminator of information about units the students aren't going to get much out of them anyway.  So by providing less information and more opportunities for the students to experience unit analysis in context I feel like I'm doing my best for them.

So what about cancelling units?

My goal is always deep conceptual understanding.  There is some problem solving in my classes but much less than in traditional physics classes.  But there is some.  So how do I answer the question, "How are students going to know what the correct units are for the answer if they don't keep track and cancel along the way?"  I get this a lot when I'm up on my unit soapbox.  Let's first address one of the central issues:  why exactly to we think (and let students think) that kg/kg = 1?

I have no evidence or experience with this.  To be honest, I am not even sure that 4/4 = 1 except that I was told that in 4th grade and I've used it ever since.  I remember in every chemistry class I've ever had using dimensional analysis to solve mol-type-problems.  And although I was proficient I never really understood how or why it worked.  But it did and that was all that mattered.

Now, I know that right about now you're probably either yelling at the screen or thinking I'm an idiot.  But let's assume that I'm not.  How does 4/4 = 1?  Or even better how does 4 apples / 4 apples = 1.

People from here have told me stuff like, "well if you take for apples and divide them into groups of 4 apples you have 1 group!"  (with indignation).  But my question is, "where did the groups come from?  There are no groups in the original statement! And where did the apples go?  Are they still there?  Are they hiding?"

Have we, as a collective group of science teachers, allowed this process to continue without questioning its understand-ability?  And think, if I am having an issue with this, what must it be like for students?
Actually I know what it is like for students: mostly they don't care.  They like to cancel units because it makes things easy for them and they don't give a shit if they understand the why.

I want to know about the why.  And I want my students to want to know about the why.

If we now take the two concepts mentioned above; unit inclusion and unit cancellation and put them together we get to the problems I've encountered with students.

Let's consider the idea of slope.  In the classroom students measure the position of constant speed buggy cars with respect to a running clock.  If the car starts some distance in front of the zero line a graph can be generated by students with a slope and an intercept.  The equation may look like:

x = 35t + 20                                         or it can look like
x(cm) = 35(cm/s) + 20(cm)

Which of these is easier to understand?  I would assert that the top is easier to understand for students.  You and I will see the bottom and understand all of the syntax.  But a student would look at the bottom and ask themselves, "Why are there so many letters?"

If we then want our students to use these equations by plugging and chugging things can go from bad to worse.  I've heard lots of students look at the bottom equation and ask, "how do I know what to plug in where?"

If you study Newton's Law of Universal Gravitation you will invariably have to deal with the Universal gravitational constant.  The value is something in the range of 6.67 x 10E-11.  But the units are N(m)(m)/(kg)(kg)  When the students get to this value and try to use it to solve a new problem, they are very confused because of all of the letters!

Why are we, as a group, so set on keeping the units intact when all we've seen is confusion from many of our students?  Unit analysis does not provide insight into the underlying physics for introductory physics students.  I think it would be amazing if it did but alas it does not (for the majority of students).

In conclusion, the traditional methods with units are fine for some students.  But I want to know, is there a better way?  I hope there is.  And I'd love to let go of the trappings of traditional instruction and brave the new world.  Let's try and see what we can do.  Students today are different from those just a couple of years ago.  I want to change and adapt.  Let's not keep doing it the old way without a real understanding of the why.  And let's help our students develop methods that work for them from their own understanding.

Wednesday, June 15, 2016

Why Teach?

The other day I was asked by a good friend to answer the question:

"Why Teach?"

I thought about it for a while and then wrote a way-too-long response.  But since I don't want to lose that thinking I thought I'd put it here too.

So I’ve been thinking on this for the past week and I think I have come to a good answer; which is I don’t know.

When I was first starting out, like 18 years ago, I was young and idealistic.  If given this question then I would have been able to provide any number of platitudes about “teaching as a calling” or wanting to “make a difference in kids’ lives”. 

However, over time the reality of teaching as a job has set in and I’ve lost a good deal of my idealism.  Not because I am less idealistic or because I have become jaded by the difficulties of the job.  But because I am more realistic about the job.  Teaching is the rare profession where it can be very challenging on a daily basis but also can be very rewarding on a daily basis.  This makes it difficult on an emotional level as well as a practical level. 

One problem that we have as a profession is over inflating our own importance.  Teachers say that they are “doing God’s work” or “doing the most important job”.  In reality the stakes in teaching are actually kind of small.  Let’s compare teaching to doctoring.  No one is going to die if I am ineffective in my job.  No lives are at stake.  Kids might not learn as much as we would like but that is actually the reality of the job anyway. 

Young and idealistic teachers have limited views of the world of teaching and of education in general.  When you’re new at a job it is often difficult to know what you don’t know.  This is actually a good thing because it keeps new teachers excited and motivated, hopefully long enough that they don't leave the profession before they get good.

So why teach?  It is hard to say.  There isn’t big money in it.  You can make a good living but you’ll never get rich.  The pension system is gone, which is tough for new teachers.  There is lots of time off, which is necessary to do the job effectively.  And every good teacher I know spends most of it working on teaching anyway.  You get to work with kids – which can be good and bad.  Politically teaching is not currently a dream job.  We are under fire from all sides about lack of accountability and legislatures are continually trying to tell us what to do.  They’ve dissolved our unions and are attacking our pensions.  Society asks us to raise their kids, to teach them, help them become productive individuals and them chastises us for not doing it effectively enough or cheaply enough. 

None of this matters to me, however.  It kind of comes with the job.  Too many of the jobs that are most important are kind of thankless.  But it is kind of a deterrent to anyone idealistic enough to think about going into teaching.

So why teach?  I guess for me it comes down to this:

Good teaching is needed. 

This sentiment is true on both the individual student level and on the societal level.
On the personal side, we can all remember the teachers that inspired us to be our best selves.  Could you imagine life without those influences?  Think about the elementary school teachers who practically raised you.  Think about that high school teacher who inspired you toward science or (insert subject are here).  Every individual needs good teachers in his life both to get them through the day and to push them toward greatness.  Without this, where would the kids be?

The concept of the “self-made man” is one that drives me crazy!  There are plenty of people (actually many very much like you) who have become successful based mainly on their own hard work, effort and vision.  But to call them self-made?  What about the countless teachers that they had in their lives?  What about the schools they went to that provided them a place to learn and grow? 

Is this enough of a reason to teach?  Maybe.

On the societal level, there is an expectation of good teaching.  Not so the kids can know more, but so that society can grow.  Look at the current political climate.  It seems, from an outside perspective, to be a debacle of monumental proportion.  But I feel that this is an amazing time.  We have arguments and debates about big ideas.  We don’t agree and have a sense that our ideas matter.  Where did all of this come from?  It came from the commitment we have to teaching.  There are lots of political concepts that make no sense, like climate change deniers.  And I feel that highlights the importance of good teaching.  We talk about these ideas because they matter.  Even if we go back to the 60s.  The political changes that took place in the 60s were a direct result of the overhauling concepts of teaching and learning put in place post world war 2.    

Is this enough of a reason to teach?  Maybe.

In my opinion teaching is not about disseminating facts or information.   Teaching is about helping students/people to learn how to learn. 

That idea – that knowing how to learn is what is important, for both the development of individuals and for the development of society – is what keeps me teaching; is in my opinion a reason to teach.

Now that I write it, it does sound kind of idealistic.  It sounds like a reason that is part of a bigger idea.  Maybe that is good.

Thursday, February 11, 2016

Block Slide Challenge

Block Slide Challenge

One of the aspects of my class that I, and the students, find most engaging are the challenges.  These are often called physics practicums but I don't really like that word we just call them challenges.

We do challenges in all levels of physics that I teach.  And I do them with the physics teachers with whom I work in the summers as well.

There is the T-Bone challenge where we try to get two constant velocity buggies to crash in the middle of the classroom.

There is the Police Chase challenge where a constant velocity buggy is chased and caught by a constant acceleration fan cart.

There is the Paper River challenge where they have to place a constant speed buggy onto a piece of paper that moves at a constant speed (it is about 3 meters wide) at some angle and it has to travel straight across and hit a target.

There is the Bombs Away challenge where students drop a sand filled balloon into a constant speed buggy from about 7 meters up.

There are lots of projectile motion challenges - from easy horizontal shoots to more complex up and down projectiles.

There is the Cup and Foil Challenge (formerly the egg challenge) where a heavy object hanging on a spring has to be dropped so that it will just touch the foil on a cup but not break through.

There is the Pendulum and Troll where they time the swinging of a pendulum to knock a troll out of a constant speed buggy.

This particular challenge happened in the AP class where they are currently studying work and energy.  Ostensibly the question is this, given a block compressing a spring; how far will the block slide before coming to a stop?

At the lab station each group has track, a block and a rubber band set between two clamps. I told them that their task was to figure out how far back to pull the block against the spring so that it would slide down the track and come to rest with part of the block hanging off the edge.

I asked them what they thought they would need to know and they responded with: the mass of the block, the coefficient of friction between the block and the table and the spring constant of the rubber band.

Some groups decided to set a slide distance and the calculate the pull back distance of the rubber band.  Other groups decided to set a pull back distance and then calculate the slide distance of the block.

Either way they chose, they were on their own.  There are no directions for this.  And they struggle!  But they are supposed to.  What I find most exciting is that they find it hard and persevere.

Here is the video of one of the groups who had first time success.

Challenges are a great way to engage your students with actual hands on problems.

Tuesday, June 16, 2015


One day to go!

So the #MiModPhys15 workshop starts tomorrow here in Grand Rapids and I couldn't be more excited.  And this year, I am nervous as hell!  What is up with that?  This is the 6th year that I've been running (with great co-facilitators) a modeling workshop; you'd think that after all of this time I'd be less anxious, not more.  But alas, that's how I'm feeling.  I told my wife, "I'm in full on freak out mode!"  I suppose once I get into the workshop room and set up I will start feeling a little better but right now I am so excited I feel like I'm going to explode.

Let's talk about Grand fired up am I that we're in Beer City?  For those of you who know me you know I'm a big time beer drinker; not big enough to brew my own, but I love a good IPA.  So to be in a place where they are plentiful excites me beyond words.  I am not sure how much it'll help my productivity but I have my list and I'm ready to get a start on it.

One of the aspects of a good modeling workshop (both my opinion and that of David Hestenes) is a community feel that comes from; 1 the group learning and 2 a sense of community that stems from social interaction outside of the workshop.  How do the facilitators create that sense?  First of all, it is difficult.  The workshop itself is a very intense 8-4 experience.  On to of that we ask the participants to do homework.  The nerve!  Does anyone really want to hang out with the facilitators and other participants after a full day of doing so with an hours worth of readings looming?

The original modeling workshops were held at Arizona State University.  That means that 
most of the participants had flown in and many were staying in the dorms together.  There was an instant sense of community because we were all staying in the same place.  With our workshop there are some people staying in hotels, some at home and some camping (at least I think there are some camping).  So how do we create this feel with such a disparate experience.  

I vote for beer.  

I don't mean that we have been during the workshop (although there are times when I am sure it would help).  But I mean more than beer that communal experiences like going to a bar that create this feel.  I would like this to be more than just something that we do in the day, I want it to be something that we reflect on for years to come; "Remember that summer when we did that workshop in Grand Rapids..." that is the kind of experience I am looking to provide for the participants.

The whole goal for the workshop is to:


Anything less is a missed opportunity.  The participants come to me having committed so much time and energy to what they hope is a worthwhile pursuit.  The goal is to help them see that not only is it worthwhile, but meaningful; life changing!  If at the end of the workshop you don't feel that I've helped you change your life, I have wasted your time.  

So how do I combine an increased knowledge of content with an advanced pedagogy and a communal, social learning experience?  Modeling workshop.

Thursday, July 24, 2014

Southwest Michigan Modeling Workshop Day 15

The last day of the workshop started with a breakfast prepared by the participants of pancakes, bacon and sausage!  It was a great way to end the workshop but it got us kind of a slow start.

Reviewing our circular motion idea from the previous day we started with a demonstration where I spun a stopper over my head and released it!  I asked for observations of where it went.  I did this several times with a stopper basically flying around the classroom!

I had them then draw a motion map for the stopper.

We then reviewed the aspects of circular motion that constitute the model.
With the major ideas in agreement I asked them to draw force diagrams for three specific situations:
1. A rider on a merry-go-round (not the one with the horses)
2. A rider on a loop of a roller coaster
3. A rider on a carnival ride called the rotor or the gravitron

In each case the unbalanced force must point toward the center!
Here is where things got interesting.

We know that the unbalanced force points toward the center.  In my classes we call this the Funbal.  Some people call it the Fnet.

Here is the key to getting this - there is a vocabulary word that is associated with this unbalanced force.  It is called the centripetal force (let's use Fcent).

The idea is this:
Funbal = Fnet = Fcent

They are all the same thing!  I gave each group a stopper on a string and asked them to spin them around and feel the factors that they think affect the force they are feeling.

Each groups comes up with the idea that more speed --> more force and that more mass --> more force.  In addition each group had an idea that the changing the radius had an effect on the force but couldn't decide if more radius meant more or less force.

So we asked them to put the three variables into an equation that made some sense to them and show how the units worked out to N.

Not the best way to do this but a quick and dirty way.
After that we checked with the Google.

They then got to work on unit 8 worksheet 1.  This was a serious struggle for them but mostly because it is really hard.  The circular motion unit is a culmination of every model that we've developed through out the year/workshop and is at the limit of most participant's understanding of physics.

I then hung the Flying Pig and asked the participants to find the tension in the string holding the pig.

It is an easy practicum challenge but the kids like it!

Then we set up a hard practicum challenge.

The idea is simple.  We gave each group 3 or 4 pieces of string.  They tested the strength of the string.  Then they created a pendulum with a mass of their choosing at the bottom.  They raised to an angle they calculated and let it swing.  Then they raised it 10 degrees and as it swung it had to break.

This is a little challenging but they got it to work!

And all of the sudden we were done.
We gave the FCI post test and had the participants do the end of workshop evaluations.
Then we cleaned up, gave out door prizes and headed off into the sunset.

Southwest Michigan Modeling Workshop Day 14

There wasn't any reading from the previous night so we just jumped right in with white boarding the speed and energy lab from the previous day.

There is clearly a square root relationship here.  I had them set the boards aside.

The next question is, "What, if any, relationship exists between the energy stored in the stretchy string and the vertical height up a ramp?"  They took the same set up and just lifted the far end of the ramp.

The more energy they put into the string (by stretching it farther back) the higher up it goes.

This one shows a linear relationship.  Again I had them set their boards aside.

Lastly we asked, "What, if any, relationship exists between the energy stored in the string and the slide distance?"

They took the original set up and substituted a wooden block for the low friction cart.

The more energy they put into the string the farther it slides.  This is somehow related to the energy relesased to the surroundings.

This relationship is also linear.

The real question is, when you have all of these boards with the correct relationships, how do you get to the actual equations?

This takes a bit of hand waving and it pretty much teacher led.  But what is the actual point?  For the students (or participants) to get a sense of the energy transfer and conservation.  The mathematical equations are only one part of the whole energy model and I don't think they should be the main focus for anything.

So what did we do?  We looked them up on Google!  Yep - I used the Google to verify that what they got in the lab actually matches the accepted equations for the different storage mechanisms for energy!

Once we were finished with the white boards they started unit 7 worksheet 3b.

Unfortunately we were on the second to last day and we skipped white boarding and discussing the worksheet :(

I wanted to get to a practicum challenge however.  Here is what we did.  For each group we set up a clamp on a table and put a long rod in the clamp.  I used a 90 degree clamp to attach a short rod to the long vertical rod.  I hung a spring on short horizontal rod and gave each group an object of known mass.  I also gave each group a small drinking cup with aluminum foil on the top covering the opening.

The task was to adjust the height of your rods to that when you released the mass, from the height of your choosing, it would touch the foil without breaking through.

The video above shows a winner!  The rest of the groups were very close - I mean within a few centimeters.

After that was all done we needed to so a circular motion intro.  I started by swinging a rubber stopper attached to the end of a string above my head in a horizontal circle.  The questions were:

- how do you find speed?
- is it accelerating?

I had them all draw the system schema for the stopper and then the force diagram.

Traditional physics students always try to put an outward force on the stopper.   However, with the system schema in place there are only two forces and no one seemed to be confused.

The last question was - in what direction is the unbalanced force?

This is a three dimensional representation of the force diagram for the stopper at four different locations.  They were easily able to see that the unbalanced force always points inward toward the center.