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They get faster

September 11, 2010

One thing I notice about modeling is that when you throw kids into labs with minimal explanation and tell them to get going, they do improve very rapidly. Today, for lab, we had about 40 minutes, and I said “Two forces we’re interested in are the gravitational force on an object and the elastic force of a spring. What do you think these depend on, and how can you test it?” 2 minutes later, everyone was hanging spring scales from ringstands with masses. I put em on the timer because I wanted to give them a mini-assessment, and break them of the perfect data habit, and all of them had 2 data sets in under 30 minutes, which was pretty awesome in my book. Previously, when I typed out this lab as a 4 page step by step process, it’d take kids 2 full hours to do, and some wouldn’t finish at all. I think it’s much better to get the kids to take data, move toward tentative conclusions, and then push them hard with some deeper questions, like realizing that the spring scale isn’t measuring the gravitational force, it’s measuring the force of the mass hanger on the hook. So how can we get away with saying it is measuring the gravitational forece? Again, careful force descriptions and FBDs can help here.

What was great is that when it came to measuring what affects the elastic force of the spring, I got some very interesting methods that are going to really be illuminating to discuss.

These guys realized you can take data a lot faster if you just skip the mass hanger altogether.

These guys are using 2 spring scales (they say they aren't the same), and adding the 2 forces to find the total force.

So the only problem with this was when I started asking this one group about why they were doing what they were doing, they instantly seemed to pick up on some vibe from me that they were doing it wrong and started to try to figure out what they needed to fix. I reassured them, and told them that if they were making a mistake, it was a glorious one that would be super-edifying in discussion, but I still think they fear being wrong most of all, and this definitely can get in the way of learning. Need to keep working on this.

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