Day 117: Vectors

Wednesday, 19 February 2014

Screen Shot 2014-02-21 at 8.39.05 PM

Medium-level difficulty classwork problem on vectors.

Classwork today was way too difficult for the kids and that one thing threw the entire lesson off.


  • the students are freshmen, enrolled in a geometry class
  • earlier this semester, they learned vectors in math class
  • earlier this year, they learned trig ratios, special right triangles, and laws of sines and cosines
  • I have not emphasized unit conversions this year

So, after a quick refresher on some vocabulary, especially component and resultant, I handed out a classwork problem set for them to practice with. Right away, I could see the wheels coming off my lesson. Kids struggled with finding the distance traveled by a constant velocity object given a velocity in km/h and a time traveled in seconds. Then they struggled to extend their knowledge into finding resultant displacements for the sums of two vectors.

Where did this assignment go wrong?

  • it didn’t scaffold appropriately: there weren’t any easy problems to build confidence on and the problems got way too hard way too fast
  • there was unnecessarily difficult language and situations (most of these problems came from a problem workbook from the Holt Physics text)
  • the refresher lesson didn’t adequately prepare students for vector triangles that represented anything but displacements
  • too many unit conversions!

So, in a teacher move I ripped off a Dan Meyer post a few years back, I put a few notes on the Word doc so I’d know how to modify the assignment next year:

"Stickie" note reminder to myself before I reuse this next year.

“Stickie” note reminder to myself before I reuse this next year.

I’ve always beat myself up over not stretching the top students in my class and have to compliment myself on doing so with this assignment. At the expense of everyone else. Now, how do I maximize the stretch for some and minimize the stress for the others? Problem choice is one method I’ve considered.


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