Today I subbed in a continuation school English class. It's in my LA County district. Since it's a high school class that isn't math, there's no need to do "A Day in the Life" today.
Officially, this is a sophomore English class, but this is continuation school, and so some of the students are older. The students can either work on a journal or on one of two drill-and-practice websites. There are also two aides who attend this class via Zoom to help them out.
One guy attending in-person doesn't have a Chromebook yet, and so I send him to the office. The next thing I know, he's using the Chromebook he receives to log into Zoom as he walks home from school! For some reason, when he arrives at the home, he's being sent home.
In this district, students must be logged in to Zoom for at least thirty minutes. Usually, this is the first half hour of the period, but for some reason, sixth period must log in for the last thirty minutes. I wonder whether this has to do with the old pre-coronavirus schedule at this continuation school, where students are scheduled for a half-day -- either morning or afternoon. (Ironically, during the pandemic, many elementary schools have this AM/PM schedule, but this continuation school no longer does -- instead following a similar Level 2 hybrid schedule as the comprehensive high schools.)
The song for today is "Patterns" from Square One TV. Also, after school I decide to revisit the two new tunes that I created this month -- "Diagrams" and yesterday's "Ratios." I definitely like the "Diagrams" tune more despite it being based on the more complicated 20EDL scale. And so most likely, I'll keep the "Diagrams" tune and convert "Ratios" to a rap -- discarding the tune I wrote after just one day. (I might even go back and edit yesterday's post -- especially once I perform that rap in a class.) I don't want this to turn into another music post, and so I'll end the music discussion right here.
Today is Friday, the first day of the week on the Eleven Calendar:
Resolution #1: We are good at math. We just need to improve at other things.
I only consider this resolution indirectly -- through the "Patterns" song, I remind the students that they are good enough at finding patterns to succeed in their math class -- whenever they have math. That's as far as I can go today since it's not a math class.
Lesson 14-5 of the U of Chicago text is called "Vectors." In the modern Third Edition of the text, vectors appear only in connection with translations in Lesson 4-6. In other words, Lessons 14-6 and 14-7 of the Second Edition have no counterpart in the Third Edition.
This is what I wrote two years ago about today's lesson:
Lesson 14-5 of the U of Chicago text is on vectors. Much of physics deals with vectors. Force is a vector quantity, as Einstein knew all too well.
I remember back when I was a high school senior taking AP Physics C, and our teacher wanted us to remember one thing about vectors:
Vectors operating at right angles are independent.
This means that if two vectors are perpendicular to each other -- most notably if one is parallel to the x-axis and the other to the y-axis -- then they are linearly independent. Motion along one vector has nothing to do with motion along the other. We notice this most clearly when one is throwing a ball, and we resolve the velocity into its horizontal and vertical components. The horizontal component of velocity is slowed down slightly by the force of air resistance, while the vertical component is slowed down -- and its direction is ultimately reversed -- by the force of gravity.
In fact, I remember learning about acceleration so many years ago, and I was confused as to why an object that is turning or slowing down is said to be "accelerating." After all, I thought that an object slowing down was decelerating. To find out the answer, we must look at vectors. If the velocity and acceleration vectors are perpendicular, then the object is turning. They must be perpendicular because of the theorem from Chapter 13 (Lesson 13-5) that the tangent and radius of a circle are perpendicular. So if the velocity and acceleration vectors are in opposite directions, then the object is slowing down. I was confused by the use of the word "acceleration" by non-technical English speakers, where it usually refers to an increase in speed without considering vectors at all.
As it turns out, we prove in Linear Algebra -- a college course beyond Calculus -- that any two vectors that aren't parallel are linearly independent. But the linear independence that we consider the most in physics involve right angles. We don't discuss this idea in Lesson 14-5, but we will look at both velocity and force vectors on the posted worksheet.
Vectors appear in the Common Core Standards, but not in the geometry section. Indeed, they appear in the "Vector & Matrix Quantities" section:
CCSS.MATH.CONTENT.HSN.VM.A.1
(+) Recognize vector quantities as having both magnitude and direction. Represent vector quantities by directed line segments, and use appropriate symbols for vectors and their magnitudes (e.g., v, |v|, ||v||, v).
(The U of Chicago text uses the first option, a single boldface roman letter. So v is a vector.) The point is that the various domains of the standards don't line up exactly with courses -- not even for the traditional (as opposed to the integrated) pathway. So there are standards that appear in the geometry section that don't appear in a geometry course (i.e., conic sections), as well as vice versa (vectors).
The various Common Core Standards for vectors are spread out among the last three lessons of the chapter, 14-5 through 14-7. One standard that appears in today's Lesson 14-5 is:
CCSS.MATH.CONTENT.HSN.VM.B.4.A
Add vectors end-to-end, component-wise, and by the parallelogram rule. Understand that the magnitude of a sum of two vectors is typically not the sum of the magnitudes.
This is only partly realized in Lesson 14-5 -- component-wise addition will appear in 14-6. But adding vectors end-to-end and by the parallelogram rule do appear in 14-5, and the U of Chicago does give an example where the magnitude of a sum isn't the sum of the magnitudes -- indeed, there's an example where the sum is shorter than one of the vectors being added! The text explains that this is to be expected since one vector is the velocity of the boat and the other is the velocity of the current (and the boat is moving nearly upstream).
So in a way, we are beginning this standard today as well:
CCSS.MATH.CONTENT.HSN.VM.A.3
(+) Solve problems involving velocity and other quantities that can be represented by vectors.
The text points out that vectors are closely related to translations. Many texts tend to define the translation in terms of its vector. The U of Chicago does the opposite. Instead, translations are defined as compositions of reflections. The Two Reflection Theorem of Lesson 6-2 tells us how to find the magnitude and direction of a translation in terms of the two mirrors. Of course, some would say that the magnitude and direction of the translation really means the magnitude and direction of the translation vector. But the word "vector" can't appear in Lesson 6-2, since it isn't even defined until Lesson 14-5. Instead, we see the following theorem:
Theorem:
Two vectors are equal if and only if their initial and terminal points are preimages and images under the same translation.
This theorem, therefore, shows how to connect the U of Chicago definition of translation (two reflections) with the definition found in other texts (vectors). Notice that in both cases, "equal vectors" are defined to be vectors with the same magnitude and direction.
This problem is resolved in the modern Third Edition of the text. Translations appear in Lesson 4-4 and vectors appear in Lesson 4-6, rather than eight chapters apart as in the old text.
Finally, the text defines vector addition:
Definition:
The sum or resultant of two vectors AB and BC, written AB + BC, is the vector AC.
David Joyce criticizes the use of the word "resultant" to refer to vector sum:
The section of angles of elevation and depression need not appear, and the section of vectors omitted. (By the way, who ever calls the sum of two vectors the "resultant" of the two vectors?)
But then again, U of Chicago rarely uses the word "resultant" and mainly uses the word "sum" -- the word that we normally use when referring to addition. Joyce would prefer to omit the section on vectors, but they are included in the Common Core Standards -- and as I mentioned, the U of Chicago devotes three sections to vectors, not just one!
Joyce would be glad that the modern Third Edition has only one section on vectors -- but then again, he wouldn't be thrilled by the emphasis on translations and other transformations in both the U of Chicago text and Common Core.
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