Exploiting classroom context, exploring physical context

Last thursday morning group#1 used the classroom context to get an initial hint to solve a problem but then subsequently spent a considerable amount of time spontaneously varying the physical context of the problem itself to buttress and refine their first insight.  The former I usually consider disappointing because it’s a kind of hidden curriculum that is not part of “authentic practice” and so is not so useful to learners outside school.  The later I consider a sophisticated problem-solving approach that I hope learners realize is a part of what it means to think like a scientist/physicist.  Further, group#1 took the idea of changing the physical context and applied it to a new and very different problem later in the morning.  I thought this showed the amazing kind of science reasoning and transfer ability that teachers can do.  What follows are the details of this scenario.

The E1 class was working on the spool and string problem.  Lane had demonstrated that pulling straight up on the string caused the spool to roll faster and faster and faster across the floor.  He reminded them that earlier that morning the class had agreed that “If an object experiences a net force in the same direction it is moving it will speed up.”  Then he gave the problem that since the spool was clearly speeding up, the groups' task was to decide what force was causing the speeding up.

The importance or usefulness of context then came up in two different contexts for table#1.  ^_^

At the start of this task (see video) Desi seems to be in a kind of classroom context, answer-making mode.  She blurts out feature-talk words (“momentum”, “torque”) that have not really come up before and cites her daughter, NPR, and the Olympics as the source of part of her knowledge.  It seems like she is grabbing for a word to label the effect Lane demonstrated.  This is not how she usually contributed to the group, so I was surprised (caution, 8 minute video; it's so interesting I wanted to show it all).

While they were still talking about what the force might be Desi then noticed (1:09 of the first clip) that Lane and Adam were filling a tub with water: 

“now they’re filling up this thing because I have a, and I’m going to make a reasonable guess they’re going to do the same thing in water and it won’t move the same way, it’s just going to spin (stay in place)”

She reasoned they might be trying to eliminate friction (she was thinking about friction all day and bringing it up in all the activities - it was interesting to see how it was a thread in her thinking the whole day when discussing slowing down or speeding up).  This is how she used the classroom context to get a hint for solving the problem.

After that initial idea spark, the group goes on to bring up many wonderful relevant examples from everyday life or their personal experience with each person building on the previous person’s thoughts, and using sophisticated reasoning like limiting cases:

(i)                 Their first example is that the wheels on a training bike have to touch the ground firmly, otherwise they won’t provide traction, they won’t spin.

(ii)               Vickie modifies the spool context further in a limiting case kind of way by talking about the spool in the air so there’s no contact with the ground (ground is lots of friction, water is less, and air is even less).

(iii)             Desi puts the two together:

“Bike tire spinning in the air, there’s still some friction being created with its contact with the atmosphere, but not enough friction to invoke, or induce movement (forward)”

(iv)             Jenna takes the limiting case reasoning and runs it backward to talk about the contact force by the floor on the spool:

“…so this force has to increase in this particular area (pointing to WB) relative to everything else”,

(v)               Desi runs with Jenna’s idea and connects to both the static case of no movement as well as the net force for speeding up:

“(the) pull increases the net force, which means force on this end changes enough so that the spool can move”

I think her reasoning here is that pulling up on the string causes the backward force to increase, so the forward friction force increases as well,

(vi)             Sue extends the context even further by discussing other ways to change the friction (aside from water or air):

“can increase friction by having a heavier spool (“right”) or having a (harder) friction surface”

(vii)           Jenna extends that idea by relating it to another personal experience of gears on a bicycle and changing the diameter of the spool (which seems to me more getting at the physics idea of rotational force or torque):

“makes me think of gears on a bicycle, so if this spool was smaller or larger, it would change”

(viii)         And then Sue brings it completely full circle by connecting the spool problem that started all this reasoning with a major previous problem – the mousetrap car (which they saw the first day and worked on the two days previous to today using both energy and force stories).  Vicki runs with Sue’s suggestion.

Sue:      reminding me of the (mousetrap) car

Vicki:  yeah, me too (draws on WB) 

Jenna:  oh, absolutely

Vicki:  (gestures with her hand, like it’s a lever arm) so instead of his hand (pulling up on the spool string) it’s the lever pulling that string (on the mousetrap car), and making it (the mousetrap car) go

I see this as expert-like listening, teamwork and reasoning as they build upon what each other says, modify the surface/object interaction to develop their intuition, and connect to previous scenarios from their life as well as what they previously studied extensively in class. 

I don’t know if they needed the hint that Desi picked up on, but they sure took off once she enunciated it.  But somehow they are not as confident as I would expect.  Because it seems like when they are all done, near the end of the clip, they go back to a kind of classroom-context type of reasoning.  Because they’ve finished early, before anyone else, they must have made a mistake, or not done something right or well.  They’re very nervous about their performance.  Vickie starts it, but Jenna joins and then Desi does too (they’re all talking over each other so I just can’t tell if Sue thinks that as well or not; she doesn’t object when Desi clearly states this nervousness to Lane):

              Sue: (looking around) are we done?  (puts red cup on top)

            Vicki: if we’re done early, I’m thinking we oversimplified it, we haven’t analyzed it enough, we’ve not tweaked it enough

           Jenna:  haven’t done enough

Desi:  That’s our disclaimer.  That’s our disclaimer every time.  We have a disclaimer (to Lane) Based on our current level of knowledge, this is how we understand the situation.

But they come back strong again on the next activity.  So after a 15 minute whole class discussion where every group shares what they did on the spool problem, Lane starts a very different activity.  The goal of this activity is to watch a video of an outdoor classroom of eight fifth graders and their instructor and try to tease out what ideas the different students might have as they explain their reasoning to their instructor.  In the video the students kick a soccer ball on a grass field and talk with their instructor about what it does and why they think it does that.

 

I won’t go into a lot of detail here but I’ve cut out two more clips from table #1 talking about what they saw in this video.  And even though it’s about kicking a soccer ball rather than pulling a spool, and even though it’s about the ball slowing down rather than the spool speeding up, after answering Lanes’ initial question table#2 very quickly starts connecting this problem to their the previous problem about the spool as well as their personal experience.  They’re playing with ideas again in a seemingly effortless way.  They talk about how what the kids did is not what table#1 did.  That the kids didn’t think about the surface, the environment, and table#2 discusses ways they could try to help their own students make sense of a kicked soccer ball.

For example, Sue talks about her experience playing soccer as a youth and how the different fields (tall grass, artificial turf ) had a huge and obvious effect that she and her teammates suddenly had to account for. And that she could use this with her students (about 55sec in):

I don’t think it looks that unobvious, I played soccer as youth, play on different fields, don’t think it would be that hard to make obvious, what’s making stop faster in big tall grass vs. making it go forever on this turf, all of a sudden they’re going to shift their perspective to a whole other object is involved.

 

And Jenna connects it back to the spool problem they just did (though I'm not sure the group takes up her idea, as Desi says "no, underwater soccer", perhaps missing Jenna's point):

Or does it matter which environment it’s in, you’re still going to be.. the same.

It’s kind of like putting it (the spool) in the water vs rollling on the floor

So again they continue with what seems to me to be an expert-like approach to physics reasoning.

So the initial classroom context of the spool problem kind of “gave” them an answer.  But they ran with it.  And really seem to have taken it up, because they were able to apply it in an entirely different sort of problem they did subsequently.

             - brant hinrichs