Middle and High School … from a Montessori Point of View
We talked about waves today down at the creek. The water was fairly calm so we could make some nice surface waves using floating leaves to show the up-down/side-to-side motion as the waves passed. I gave them 10 minutes to “play”, and more than one team tried to make a tsunami.
Since it’s allergy season, one student who could not go outside, read the chapter on the characteristics of waves and prepared a short–5 minutes–presentation for the rest of the class when we came back in.
Balloons are the best way to demonstrate static electrical forces.
One of my students asked me, “Can we spend next week working on our machine?” And I said yes.
This was a week and a half ago. I’d planned on to starting the discussion of conservation of energy as we transition from mechanical to thermal and electrical energy. However, I find it hard to resist when students ask to pursue an area of work. Students learn a lot more when they’re intrinsically motivated.
So, after the request to continue working on the machines I did an informal survey to see if the rest of the class were interested. They were quite interested, and the vast majority really wanted to continue on their projects — or something similar — rather than just having an opportunity to slack off.
I, therefore, let them have the time. My only requirement was that they state an objective for the week.
One group’s goal was to build a complex machine with 500x mechanical advantage. Another student — I let them choose their own groups or work alone — simply wanted to build a working pulley system; something he been having trouble with all month. A couple of other groups wanted to build robot projects.
And they went at it. All week long students would come into class eager to work. On Wednesday I got back into the science room a few minutes late for class, and they were all in there working away. It is a wonderful thing to be able to walk into a classroom with the whole class on-task and combining their new knowledge with their creativity.
Of course, after the first few days the projects evolved. I gave one group a Lego microcontroller and a quick lesson to help them activate the second part of their pulley system.
Another group quickly finished their robot and wanted some sort of track that it could follow. I did not have a track, but digging around in the store-room uncovered our track building kit — one of the ones with loops and jumps that’s great for learning about inertia, and conservation of energy. I also helped them out by giving them a fire pit (with green flames) for their marble to jump.
In retrospect, I realize that I should also have had them keep a daily diary of their work — I had to settle for summary at the end of the week instead — but they did some really exciting, self-directed work that I was really proud to see.
A couple weekends ago, I took my kids to see the Deutsch Country Days. It’s one weekend each year where they set up a 19th century German immigrant village in Marthasville just east of St. Louis. They make cider, cheese, candles, rope, tin ornaments, and a lot more on the spot. You can see the wonderful household mechanisms in old log cabins and watch blacksmiths at work. But my favorite part had to be the sawmill where they were cutting large logs using a large, ~75cm, diameter blade powered by an actual steam engine.
The big boiler pipes steam into the engine which turns a wheel and axle, which drives a large belt, which connects via another wheel and axle to the large blade. It’s a nice example of a complex machine, which the middle schoolers have been discussing in class.
It was a great way to spend a wonderful fall day.
To summarize what we’ve been doing this past quarter in Middle School Science, we’ve compiled this handy little reference table of the equations for motion (mechanics).
Since we’re studying forces and mechanics in science I’ve asked students to keep an eye out for any simple machines we encounter at Heifer.
I had one of my middle school student groups try a conservation of momentum experiment that, while they made it out very well in the end, did not do a good job of conserving momentum.
The students rolled a marble down a ramp by itself and measured its velocity across a horizontal track. The velocity measurement let them calculate the marble’s momentum across the track since they’d measured the mass of the marble before rolling it down the ramp:
momentum = mass x velocity
Note that since mass was measured in grams (g) and velocity in centimeters per second (cm/s), their units of momentum were gram-centimeters per second (g cm/s).
That was the easy part.
Next they put a second marble at the bottom of the ramp as a target, so the first marble would hit it and redistribute the momentum.
Because it was a collision between two marbles, there was no easy way to make the collision sticky, so they ended up with two marbles moving off at different speeds. Measuring the speeds of the two marbles at the same time was tricky, but they got it done.
Finally, they could calculate the momentum of the two marbles at the end, and the combined momentum should have been equal to the momentum of the one marble from before if momentum had been conserved.
When they did the math, the marbles after collision had about 80% of the momentum of the single marble. This difference allowed them to explain, in their presentation, that momentum was not completely conserved — and in real life it almost never is — because some energy was lost in the collision. Fortunately, we’d already had the presentation on friction so the context of energy losses, and resistive forces could be incorporated into the discussion.
I suspect that some significant portion of the difference in momentum measured was due to the fact that they were using stopwatches to measure the time the marbles took to move between two markers on the track. I’d love to have a motion detector or photogates for this experiment.
