Day 18: Projectiles and Poor Choices

Physics: I handed back exams and they worked on corrections and asked questions. I even got an, “I love you, Ms. Monticue!” Never gonna turn that down.

Honors Physics: Today was my one-on-one meeting with the new head of the upper school, and I talked to him about trying some crazy things with the honors class after this term as a test of new class formats. I decided to get the kids’ input on what topics they wanted to learn and gave them the choices of thermal physics, waves and optics, modern physics, cosmology, electricity and circuits, and electromagnetism. After looking at the data, if we do cosmology (which requires understanding waves/optics and some thermal physics anyway), modern physics (nuclear/atomic/baby’s first quantum), and all of electricity and magnetism, everyone can have at least two topics they rated as most interesting to them and only one person rated any of them “Not interesting in the least”. I’ll see what I can do to make it interesting for them. Anyway, we’ll finish out this term with energy, circular, and rotational motion and then jump into Cosmology. I’m super duper excited about the future.

After the survey, we debrief’s this week’s lab, and turns out the wildly unstructured format led to some less than ideal results. After we walked through all the measurements they should have taken but didn’t end up taking, the write-up is a reflection on “what I would change if I were to do this lab again or when designing future labs” rather than a report on the contents and conclusions of the lab itself. I consider that a really important aspect of lab work, and reflecting on an abject failure that is impossible to fully analyze I hope is a valuable exercise. Either way, I’ll be able to point back to this lab and remind them that analyzing their proposed system FIRST and making sure they’re taking all necessary measurements is more important than immediately grabbing materials and hanging things from places.

I thought class ended ten minutes before it did (which it does on Tuesday/Thursday), so I suddenly had ten minutes to work with. I had already planned for next week, so I just started Monday’s activity early and let them get started thinking about it. I described inelastic collisions and asked them just how much they wanted to push a car so it hit another car over and over again at fairly slow velocities and time everything by hand since we don’t have any sensors. We all agreed that was largely a waste of time, and since they understand the basic set-up of the experiment, I gave each group a set of data with a different control variable (moving mass, initial speed of moving mass, and mass at rest) and measured the final velocity for each combination. Their job is to find patterns in the data. It would be ideal if they could see all the collisions and get an intuitive feel for what happens, but we really don’t have the equipment necessary to do that, so I am doing the best I can and adding to a shopping list for next year or possibly a month from now when we cover momentum in AP.

AP Physics: Projectile motion! I started with the basic definition of free fall and went through some basic exercises using the CAPM model to discover everything we could about a dropped ball and then a ball thrown directly upward. Then the ball rolled off a cliff the same height as the first one. Then a ball rolled off the ramp with the same vertical velocity as the second problem and the same horizontal velocity as the third one. They were able to put everything together pretty quickly, even the kids who have been struggling, which was really wonderful to see. Then I made a mistake in both classes. I the first class I tried to write a practice problem on the fly and it didn’t actually have a possible solution. The next class I tried to re-write it on the fly and ask a slightly modified version, and it became unbelievably challenging and bogged down in a ton of algebra that was utterly unhelpful in terms of understanding projectile motion. So 1) I need to review why the question has no answer with the first class and 2) go through all the algebra and make up a full solution for the second class. Also, NEVER DO THAT AGAIN. Good grief, what was I thinking? I had a million resources I could have used to give practice problems that are reasonably well-vetted, but I got excited and started making things up. There’s a time and place for that in problems where I have a good sense of what numbers to use to get a reasonable answer, but turns out I don’t have that sense for projectile motion. Lesson learned.

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