Plan: return first homework assignment, answer questions about the second. I hope there are enough good ones to move the rest of the discussion of the use of units.
Homework isn’t “graded” – I’ve made extensive comments, and marked a few as “check-plus”. Those students seem really to have grasped how to think about Fermi problems and, more important, how to write about them. For the first time in a long time I’m not (yet) really worried about any of the other students. Everyone who turned in the assignment (all but two of the class) got far enough so that I could make suggestions for strategies to improve (e.g. read carefully, write full sentences). I hope/suspect submissions will be markedly better next week, (The first question on that assignment is to read the solutions to this one and write about what you’ll do differently from now on.
I think the class went well – perhaps too well. There were essentially no questions on the homework due next week – and people said they’d in fact started it. But I’m not so sure. But I moved on, after a short discussion about whether it was worth learning a new method to solve a problem you could do in high school (e.g. “cross multiply”). As usual, the answer is “it depends”. I hope to convince folks next week that the 1+ trick is really worth learning for percentage calculations.
Did a unit price from the supermarket question, showing that applying a cents off coupon could reverse the unit price inequality between the small and large containers of orange juice. Along the way showed how google could do all the work.
Showed that you can’t average speeds.
At the end of class one student finally got up the courage to say that he understood the problems in class, mostly because I did all the work pulling the numbers out from the words, but that at home with the problems in the book he had trouble figuring out what the numbers meant. He’s absolutely right. I wish he’d said it sooner. I will spend more time reading from now on …
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