Day 19: Technology: It was all worth it!

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Yesterday I spent an hour or so problem solving why LoggerPro wouldn’t allow us to insert videos. Today I spent an hour and a half uninstalling and reinstalling LoggerPro so that it also installed quicktime. Before this I had to spend 2-3 hours problem solving network connections with the damn things.

It was all worth it today.

Today my last class was having a board meeting, looking at v vs. t graphs for carts released from rest moving down an incline. Some groups had curved v vs. t graphs, others had linear. Discussion ensued. Is it curved because yours is a shallow ramp? Longer? What makes one curved and one linear? One person gave an elaborate and well phrased description of how it would make sense if the graphs curved, as something going down a hill speeds up slowly at first and then faster towards the end. The other students bought it.

I looked at the clock. If I did this we wouldn’t ‘get where we needed to be.’ I decided it was worth it. I had the groups go back to their computers and reload their video onto a new LoggerPro file. Then I told them to be very careful when they clicked as the cart went down the ramp. All but one group got nice, linear velocity graphs; the group that did not was skipping 4-5 frames for each click, so I asked them to fill in their data with more clicks. Sure enough, linear.

In the past I would have either told them it was ‘supposed’ to be linear or we would have had to come back to it on a day that we could reserve the computer lab. Now we were able to instantaneously, scientifically determine the answer to the question at hand. Awesome.

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3 Comments on “Day 19: Technology: It was all worth it!”

  1. EKphys says:

    Nice!!! Love the combination of the whiteboard session and the LP video work. Can you describe how you weave those together?

    • Thanks Eric! They do the LoggerPro analysis, then we whiteboard different aspects. I had them first WB the v vs. t graph, where they first decide, hopefully, that it appears that velocity is changing linearly, which was what this post was about. Then through dialogue they are guided to figure out that the slope means how much the object was changing speed every second, which we then define as acceleration (I talk about how it can be speeding up or slowing down), and how the intercept is probably zero (we started from rest; this is when I introduce them to the 5% or 10% rule of thumb, which basically says that if the intercept is within 10% of the max absolute y value, then it is probably supposed to be zero). Then we move to the position vs. time graph (another day), which I have hinted to them to use a quadratic fit (they try linear and the R is ok, but I ask them if it really looks linear…then ask ‘what’s the next step up in complexity from linear? They usually answer quadratic to that, without that question they almost always try exponential). So it’s quadratic, and we have a conversation about what that is…so far in both cases someone came up with the idea that it is traveling further each second, so the y values have to increase with each incremental increase in the time. Then we move on to the values of the quad fit, and again, someone eventually notices that A is 1/2(acc), which is fun. Then we get to B and C in similar ways. I also like to introduce unit analysis here, so that they can figure out that B must have something do do with velocity so units work out, etc.

  2. […] someone to give me 10 laptops to use in my room. The very first day they were ready I ran into an interesting problem with some data students had collected. Some said the data indicated a linear relationship, some […]


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