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2011 August 25

Physics Lab 1

I asked physics teacher John Burk for advice on putting together labs for homeschooling my son in calculus-based physics using the Matter and Interactions book (see School decisions part 3 on the decision to homeschool).  He was kind enough to pass on my request to the readers of his Quantum Progress blog: The ideal lab experience for a homeschooled student.  He also gave me a suggestion for a piece of lab equipment we could use for a number of experiments in Newtonian mechanics: an ultrasonic rangefinder.

This post is my first attempt at a physics lab assignment for my son. (Note: we are also hoping to use tech writing this year to satisfy some of his English requirements, so the assignment is a bit heavier on the writing than might otherwise be appropriate for a physics class.)  The exploration in this lab is more engineering than physics, but familiarity with measuring tools is a good place to start, I think.

I welcome feedback and suggestions, particularly from those who have taught physics!

Lab 1: ultrasonic range finder


Research how an ultrasonic range finder works (note: as of 25 Aug 2011, the Wikipedia article is a terrible stub—other sources will be needed).

Write: Write a paragraph or two explaining how an ultrasonic rangefinder works.  This should be at a reading level and level of detail suitable for replacing the current Wikipedia stub. Explain what determines the precision, accuracy, and range of the range finder.  How frequently can it measure the range? How is the speed of sound involved?  What does that depend on … ? Why do some have one transducer and others have two?  Audience: new robotics club members (technically interested high school students without prior knowledge of physics or electronics).

Bonus audience: if the writeup is good, it can replace the current Wikipedia stub.

Read the product information (and data sheets when possible) for at least 3 different (cheap) range finding modules like the following three four (added one more 1 Sept 2011):

Choose one of the range finders for us to buy.

Write: justify the choice in writing, doing a comparison of the advantages and disadvantages of each choice.  Give URLs as citations for data used in making the choice.

Sketch out in pseudocode the program needed to read the sensor on the Arduino using a simple busy loop.  What will determine the precision and sampling rate of the measurements?  What will the code do if there is no object in range of the sensor?

Advanced option: sketch out pseudocode for using interrupts instead of a busy loop.

The Lab Proper

  1. Hook up the rangefinder to the Arduino and program the Arduino to keep taking measurements and reporting them to the serial line.
  2. Calibrate the sensor by placing it at carefully measured distances from a hard wall and recording the readings.  Repeat at several different distances.  (Record temperature, humidity, and barometric pressure, if possible.)
  3. Plot the sensor readings vs. the actual distance.
  4. Do linear regression to get predictor of actual distance given sensor reading.  (Caveat: need to plot distance vs. readings rather than readings vs. distance to get best fit for calibration.)
  5. Modify Arduino code to use the calibration parameters to provide better distance measurements.
  6. Re-calibrate using new code.  What is the accuracy and precision of the measurements?  What range of distances can be measured? Is the accuracy better expressed in terms of absolute error (±1cm, for example) or relative error (±5%, for example)?
  7. Open-ended: Experiment with detecting different targets (maybe flat targets from wall size down to the size of a quarter, maybe targets of different materials, maybe spherical targets).  What effect does target size, shape, material,  … have on range and accuracy of the measurement?

2011 August 23

School decisions part 3

Following up on School decisions and School decisions part 2, where we had decided not to accept the opening at Pacific Collegiate School and not continue at SCHS, we started this morning considering homeschooling through Alternative Family Education (AFE) and a relatively new  private school, Monterey Coast Prep, whose mission statement sounded quite promising:

Monterey Coast Preparatory empowers gifted and talented students, including those with learning differences, to achieve academic, social,and emotional success.

I sent email to both schools last night and talked with both on the phone this morning.  Both schools are very flexible and would be willing to make the necessary adjustments to make the English work for us, but Monterey Coast Prep does not this year have many of the courses that we would need.  Last year they had several courses that he could have taken, but that cohort graduated and this year they did not have enough students at the appropriate level to offer AP science courses or Spanish 3.  The principal told us that she could give credit for courses taken elsewhere, but that we’d be paying $20,000 for a transcript, which did not strike her as a reasonable use of funds.

So this afternoon we registered at AFE, as they were willing to accept all our plans for how we could get through the school year, and sign the “high school release form” that allows him to do concurrent enrollment at the community college for Spanish 3 (if he can get in—the sections of 30 are all full and have waiting lists of 15).

Here are our current tentative plans for his education this year:

  • Science:  calculus-based physics using the Matter and Interactions book and VPython to do computational modeling. He and I will work through the book together, as I haven’t had physics since an algebra-based course in high school in 1969–70.
  • Computer Science: he is doing a science fair project this year, and we’ve already arranged a mentor from the University for him.
  • Math: Art of Problem Solving’s online calculus class. He had a great time in the precalculus class in the spring (and got an 800 on the SAT2 Math 2 test), and the same instructor is teaching calculus in the same time slot this year. (See Good online math classes.) We had registered him for the calculus class this summer, since he wanted to take it no matter where he went to school.
  • Engineering: We plan to continue the robotics club, but it won’t be affiliated with SCHS any more.  We’ll probably open it up to high school students from any of the local high schools.  Details still to be worked out.
  • Theater: we’ve registered him for the West Performing Arts fall teen production at West End Studio Theatre (Egad! The Woman in White).
  • Spanish: we are trying to get him into the Spanish 3 class at the community college, or the Spanish 4 class at the local high school.  In both places he will be last on the waiting list, and allowed in only if there is room.  We think that it is likely that he won’t get in this fall, but will be able to get into one or the other in the spring.
  • History: we’re thinking of using Joy Hakim’s The Story of Science series to do the history of science, with some “world history” reading on the side to put things in chronological context.
  • English: we’re planning to decouple reading and writing.  The reading will be some long list of books that are worth reading, possibly made by merging the reading lists of several local high school classes.  The writing will be technical writing (science-fair lab notebook, turning the science-fair report into a properly formatted and researched technical report or journal paper), creative writing (he has an idea for a novella, which probably won’t get finished, but we may get a short story or a play out of him), and some informal writing (perhaps a blog).

This will be our first attempt at home schooling, but several of the parts of the curriculum are things we have done before (AoPS math, WEST theater, robotics club, science fair) and it will be nice to have them be considered part of his schooling, rather than purely extracurricular.

2011 August 22

School decisions part 2

Filed under: home school — gasstationwithoutpumps @ 23:28
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The stressful weekend deciding between Pacific Collegiate School (PCS) and the public school he would otherwise be attending (SCHS) is over. (See School decisions for the dilemma.)  And the winner is …


Santa Cruz County has several breweries

Filed under: Uncategorized — gasstationwithoutpumps @ 05:14
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In today’s Santa Cruz Sentinel, a paragraph in the article First of its kind business brewing in South County: Corralitos Brewing Co. gets county OK caught my attention:

Corralitos will be the county’s sixth brewery. The others are Boulder Creek Brewing Co. in Boulder Creek, and Seabright Brewery, Uncommon Brewers, Santa Cruz Ale Works and Santa Cruz Mountain Brewing in Santa Cruz.

I hadn’t been aware that we had that many breweries in the county (I would have put the number at 3, I think, since I don’t think I know Uncommon Brewers or Santa Cruz Ale Works).

Great Britain has around 500–600 breweries for a population of 61.8 million, or about one brewery for every 100,000—125,000 people. So Santa Cruz County is doing well to have 5–6 breweries for 262,000 people (one for each 43,000–52,000 people).

(GB brewery counts from the Campaign for Real Ale

Population figures from US Census Bureau via Google.)

2011 August 21

School decisions

Filed under: home school — gasstationwithoutpumps @ 14:54
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I have recently been stressing about my son’s education (as I do far too often).

The most recent stress came from the unexpected opening of a slot in 10th grade at Pacific Collegiate School (PCS), a local charter school with an AP-intensive curriculum that is very difficult to get into.  We’ve been in the lottery for 7th, 8th, 9th, and 10th grade openings, and the best we ever got was 20th on the waiting list for 0 slots (which was for 10th grade).  So we had dismissed PCS from our educational thinking.  But Friday morning we got a call from the school that they had a slot for him—did we want it?  School has already started there, so they want a very quick decision so that he would either start school Tuesday morning (a week after the rest of the students) or they would continue going down the waiting list.

I’ve never been good at quick decisions (and I think my son shares some of this difficulty), so we spent a big chunk of Friday talking with various people about the tradeoff between PCS and the public school he would otherwise be attending (SCHS).  We are still considering homeschooling and a couple of private schools as backup options, should the public schooling not work for him this year.

Here are some comparisons between PCS and SCHS:

Both schools have good drama teachers, but the class size is smaller at PCS, they have multiple levels of drama class, and they have a reputation for first-rate work, while SCHS has one huge class that includes both dedicated actors and slackers. Both have productions outside drama class, with about the same number of students involved.  He’s had the teacher at SCHS for drama already and likes her, but would probably learn more from a new (to him) teacher at PCS. Slight plus for PCS.
Both schools alternate years of AP chem and AP Physics, but they are not in sync.  PCS offers AP Chem this year, and SCHS offers AP Physics.  He is more prepared for physics than chem, since he already has a fairly Newtonian (rather than Aristotelian) view of physical phenomena and has read several popular books on physics. Slight plus for SCHS.
The SCHS Spanish program is a bit slow, and Spanish 3 there (which he took last year) was just a repeat of Spanish 2 from his previous school (same text even).  We don’t (yet) know what level Spanish he would take at PCS (Spanish 3 or AP Spanish). Probably slight plus for PCS, but not clear until several weeks into the year.
Both schools offer AP Calculus BC, but he is pretty intent on taking Calculus as an online class from the Art of Problem Solving (we’ve even paid for it already).  Neither school gives credit for that, unless AoPS gets accredited.  Both also offer AP Statistics, neither has anything past calculus, and both give credit for classes at the community college or university.  A tie.
Computer Science:
SCHS offers none, PCS has one AP CS course. This is a clear plus for PCS.
10th grade history at PCS is AP World History, which is more intense than the more generic high-school world civilization course at SCHS. The extra reading and higher-level discussion would be a plus, extra writing (which is difficult for him) would be a minus. Probably a wash, but it depends on how much of the higher AP workload is reading (easy) vs. writing (hard).
This is the sticking point, since he seems unable to write the literary analysis essay that is essentially the only thing that English teachers have them write, in both schools.  (I’ve complained about that before in Death to High School English.) We need to find out how flexible the individual teachers are to allowing different forms of writing and different modes for showing reading comprehension.  Either school would be a disaster with an inflexible English teacher or one who had the wrong idea about how to solve his writing problem. This is the most important question for us, but it is almost impossible to know ahead of time which school will be better—even after talking directly with the teachers about the issue.  If this fails (at either school), we’ll probably have to switch to homeschooling or try Monterey Coast Preparatory School, which has this sort of flexibility clearly in their mission statement.
 SCHS has block schedule with 3 (or 4) 90-minute classes every day 5 days a week.  All courses last a semester, so the fall and spring schedules are completely different courses. This works well for him.  PCS has 6 courses that last all year, with block days (for labs) every other week—a more complicated schedule and one that makes balancing different homework load difficult.  If he gets lucky with his schedule, he can start later in the day at SCHS. Slight plus for SCHS.
He has acquaintances at both schools and is well tolerated by his classmates at either one. He has no close friends and no enemies at either.  PCS is smaller, so he’ll end up knowing (and being known by) a greater fraction of the student body.  PCS (as an AP-intensive school) has a much larger percentage of academically talented and hard working students than SCHS, but in absolute numbers the difference is not enormous.  Overall, probably a slight plus for PCS.
At PCS, he could end up with anywhere from 1 to 4 AP classes, and they have a reputation for piling on the homework.  He has a science fair project he wants to do, he wants to take (and is already registered for) the AoPS Calculus class, and he wants to continue with robotics club (currently affiliated with SCHS, but we’d already considered opening it up to the other high schools even before we got the PCS offer, so that makes no real difference).  It isn’t clear that he’d have time for everything if he ends up with the stereotypical PCS workload, though only the AP World History and English 10 look like they would take significant effort. Plus for SCHS.
Academic level:
he has trouble handling boring classes, so the higher academic level of the PCS classes may cause less trouble than a lower workload at SCHS. PCS has a pretty high concentration of gifted kids but not many highly gifted—as a lottery-entry school they have no way of selecting students other than self-selection of applicants.  It does have a very AP-intensive curriculum.  Students graduate with an average of about 5 AP passes: with a graduating class of 55 students, last year they had 420 AP classes taken, 337 AP exams taken, and 300 AP exams passed with 3 or better—obviously students are taking AP classes and exams starting with 10th grade, not taking 8 AP classes their last year, as PCS students only take 6 classes a year.)  At PCS, SAT scores are good, but not spectacular (averaging 630 in reading, 610 in math, 626 in writing—about 86th percentile).In contrast, SCHS averaged 550/562/543 on the SAT (about 67th percentile) and had 116 AP exams taken and 93 passed for a graduating class of 270, or about 1/3 of an AP class per student.  Also, SCHS only has about 56% of its graduates “4-year college eligible”, while PCS has 100%, so there are some pretty big differences in the academic climate of the 2 schools.Plus for PCS.

The schedule he’d have at PCS would be

AP Computer Science
AP Chem (or regular chem)
Drama 3 (or Drama 2)
AP World History
English 10
Spanish 3 (or AP Spanish)

On Monday he has assessments for Spanish and Drama (and maybe for chem as well—no reply yet from the teacher on that).  We’ve also got an appointment to talk with the 10th grade English teacher before school, to see how much flexibility there is in the writing assignments, as that is likely to be the make-or-break factor this year.  The workload on the English teacher at PCS is not much lighter than at SCHS (I’m guessing 80 students total vs 100 students), so it is not clear that the teacher has more time for differentiating instruction—it’ll come down more to a question of pedagogic philosophy and teacher flexibility, which are very much individual rather than school-wide characteristics.

It is interesting that the UC course approval list has not been updated since 1970, long before on-line courses existed as a possibility. Computer-savvy folk will recognize the date as the UNIX epoch (a zero in the date field in the database).

One amusing thing that came up in the course of our discussions. The assistant principal suggested we look at Aventa Learning for accredited on-line courses, as several students had used them to fill gaps in their requirements. We looked at the University of California “approved course list” for Aventa and saw no approved courses, and that the “last updated” information was ridiculous.

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