Day 33: Mirror Lab Day 1

Monday, 29 September 2014

Struggle of the day: sighting the reflected ray of light from an image in a flat mirror. Here are the ways I’ve seen it done wrong:

Points the tip of ruler at the image rather than the entire edge of the ruler.


Points the other tip of ruler at the image of the pin.

So I went to a colleague to brainstorm other ways to teach kids to get a sightline. Maybe have them look through a straw?
I tried it. Tough to see through. The colleague then suggested practicing with sighting the clock. Step 1: get a ruler and a clock.

Step 2: grab both ends of ruler with your index fingers. Point both fingers at center of clock.

Not like:
imageOr any of a million variations that are ALL WRONG. Three more sets of guinea pigs students tomorrow to test with.

What was the warmup today in 7th and 5th periods?

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I wrote this based on homework questions the kids were grappling with. Upon working this problem, I learned their biggest issue is figuring out how to convert into and out of units such as gigahertz and micrometers.

This day last year: Day 33: Final Instruments Due

Day 24: WarmUps

Tuesday, 16 September, 2014


I posted several practice problems (different kids so same problems as yesterday) to work through together before unleashing the kids on classwork. This kid does a decent job of summarizing the problem as she takes the solution.

This day last year: Open Work Day (looks like I was beginning to embrace the “work on one of these 3 things” kind of day)

Day 18: Natural Frequencies

Monday, 8 September 2014mitre saw mc
Today I taught a freshman to operate the mitre saw in our workshop. She’s building pan pipes and was thrilled at the prospect of not sawing everything by hand. I don’t think I’ve seen someone so scared of a power tool in my life, though. By her third cut she was at least looking a teensy bit more comfortable.

In class, we learned about natural frequencies & resonance through a few demonstrations and newsreel footage I like:

Next year, this talk will go before the harmonics so as to flow better. I jumped into harmonics and standing waves so the kids could know how to calculate for their musical instruments.

Falling behind is something I constantly worry about. Especially when last year I had to shorten my electric circuits unit so much at the end of the semester. Upon reviewing this blog from last year, I see I’m going to finish the unit on Sound & Waves earlier than last year. Bam! Another great use of the 180 blog — Lesson Planning in Retrospect™.

What was the warmup in 4th and 5th periods today?

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Hahaha! It’s the same warmup I used on the same day of school last year.

This day last year: Mary Had a Little Lamb


Day 10: Great Warmups

Tuesday, 26 August 2014


In two of my classes, the warmup: What is ultrasonic sound? Who is Banshee from X-Men and what’s his power?

Pictured above, the warmup in the other two: Rank the pictures waves from greatest to least wave speed. (Given wavelength, all frequencies are identical, and amplitude.) Our first ranking task and it was a great success!


Ms. P, librarian, shares about library resources available for the musical instruments project. Kids write a 3-5 page research paper for this one.

Day 169: Partial Credit

Friday, 9 May 2014

Student work I’d rather not see next year.

I’ve written before about my system for partial credit but one paper from today’s quiz has me thinking again how I can improve this system I already like. The system rests on the confidence I have that students can explain a correct solution given the answer to the problem.

Above is a kid who struggles to earn partial credit through an approved method: either correctly identifying his mistakes or by showing a (new) correct solution. Instead, he always tags his mistakes as “math” errors with no indication of what exactly the error was, which is totally unhelpful to him or me.

Oh, and for the curious, here’s the question he was attempting to solve:

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My goal is to have kids do one of the following when correcting tests:

  • spot and circle a silly mistake such as a dropped negative sign, a misplaced decimal point, or a small algebra error — which results in automatic 3/4 credit for the problem;
  • fix a physics mistake such as assuming an incorrect initial velocity or misapplying the Conservation of Momentum — which results in between 1/4 and 3/4 credit for the problem; or
  • realize they totally screwed up a problem and (given the answer) show a full & complete solution alongside their original (wrong) work — which results in 1/4 credit for the problem, assuming nothing they wrote before was correct.

While the above list focuses on kids correcting work after they’ve submitted the test, they can also earn partial credit for showing work initially that’s correct. For example, the kid who identifies all the variables in the problem gets 1/4 credit, the kid who chooses the appropriate equation to apply gets 1/4 credit, and the kid who draws an appropriate sketch gets 1/4 credit.

Day 165: LoCoE

Monday, 5 May 2014

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I spent a good deal of time today applying Conservation of Energy to solve a number of problem types. Above is one of about 5 I solved. This one in particular was fun because some kids wanted to know the height of your friend. That led to a great conversation that used words like insignificant and negligible (turns out the velocity wavered about 2%).

Oh, and we decided the abbreviation for Law of Conservation of Energy, LoCoE, is pronounced like loco in Spanish.

What was the warmup in 4th period?

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Today I learned (TIL) that about 20% of my students can’t stand roller coasters and 1.6% of my students only thought they didn’t like roller coasters. Six Flags this past Friday was an interesting experience for the latter group…er, kid. He rode the biggest ride in the park first and loved it.

Day 124: Bowling Ball Forces

Friday, 28 February 2014


The winning relay team begins their race.


Victors got their names on this meaningless trophy I keep on hand.

The first class to land upon the Forces unit happened to be my 5th period group. Above, you see one of the kids navigating a simple obstacle course with only a rubber mallet and a bowling ball. I asked them to note three moves for discussion later:

  • How do you accelerate the ball?
  • How do you stop the ball?
  • How do you turn a corner?

We timed everyone and I awarded space for their names on the meaningless class trophy, pictured above.

What was the warmup with 5th period?

Before we played with the bowling balls, I showed them this question:

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Day 110: Recognizing Terminal Velocity

Monday, 10 February 2014

Make an object that reaches terminal velocity quickly and film it.

Make an object that reaches terminal velocity quickly and film it.

I feel like last Thursday/Friday I struggled with the video analysis assignment. I asked the kids to drop a ball and film it falling. The plan was to use those videos to eventually build a computational model of an object falling with drag. Problem is there’s not nearly enough data in a 3m fall to even see the drag at work. The accelerations were still really close to g. My “duh” moment.

Enter today: the kids answered a warmup question (it’s below) about terminal velocity. Most correctly identified that their objects from Friday didn’t reach terminal velocity because they were still accelerating when the object hit the floor. I next asked them to build something out of paper that would reach terminal velocity quickly. “What would that look like?” “I dunno — give it your best shot.”

By the end of class, these kids had short videos of papers floating their way down to the ground veeeerrrrry slowly. I think we can work with this.

What was the warmup in 7th period?

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