Day 92: Whiteboard Speed Dating and a Common Misconception



Today we finished up unbalanced forces by working some problems whiteboard speed dating style. I gave each group a different colored marker, and they then had to pick up on the problem where the previous group left off. I really liked it for a couple reasons.
1) It was a change from the normal whiteboard routine
2) It forces students to evaluate what someone else did so they can continue that work
3) It forces students to think really hard about the problem in different ways, as different groups draw different diagrams, etc.

I was very happy, and the preliminary, though not anonymous, feedback from students was positive.

In my college level class we finished whiteboarding one of the central force worksheets. I was blown away by a misconception that many of the groups shared, shown by the whiteboard below. This was a yo-yo spun in a vertical circle in the counter-clockwise direction.


I think this was my fault, to some extent, for language used earlier in the unit. They really wanted the vertical forces to be balanced on the right and left sides, so that the net force was all centripetal. It led to a great conversation about how the net force can be comprised of centripetal and tangential components.


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