Day 21: Positive or Negative?


Today we were working on practice 1 problem b (again stolen from Kelly O’Shea), which asks students to find the acceleration of Object B represented with the v vs. t graph below.

Screen shot 2013-09-30 at 8.14.52 PM

After significant discussion they were fine with the acceleration of A being -1. The student who presented this was re-solving the problem on the front board, and said “so the acceleration is obviously negative,” after which he very carefully and obviously drew a line through the negative to make it a positive. Hilarity ensued.

We discussed this for quite some time before finally coming to a consensus that the acceleration was in fact negative.


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