Day 46: A Physics Mystery… Also Sagan Day

Thursday, Nov 9

It’s Carl Sagan Day! He would have been 83 today. I’ll talk about school stuff for sure, but first I want to talk about the Sagan that is currently in my life.

We named our boy kitty cat Sagan in his honor. He’s black and speckled like the night sky, and if you shine a bright light on him he turns the color of a light-polluted night sky. He’s about 9ish, a shelter cat we picked up about six years ago that they told us was 3ish, but who really knows with adult cats picked up out of the forest in Northern California. Sagan has never been the most balanced of cats due to an inner ear situation, and this summer his back legs started collapsing out from under him. The vet told us, “Yep, his back legs don’t work. It’s true,” so now we have one and a half working cats. He can drag his sorry little kitty butt around on our wood floors, so he does a lap every few hours to check things out and make sure everything is still in its proper place. He can’t, however, drag his sorry little kitty butt into the cat box, so we either express his bladder by hand, or, if we let it go too long, change out the towel and pee pad he lays on in his kitty bed. For poop, we just have to check under his tail every few hours and pick it on up. There’s not a lot of other options.

As long as he’s a happy kitty who still eats and wants pets and drags himself around to lay in sunbeams, we’re not willing to put him down just because his care is inconvenient. Heck, we took him with us to LA a few weekends ago because no vet would board him. He’s a good traveler and a good kid, and I wanted to post about him today because it’s Carl Sagan Day, and he’s my little astrokitty.


I guess for fairness sake I need to post about Miss Bug next week, huh?

Physics: Started with a quiz, and then we talked about “normalforcelessness” or, as most weirdos call it, ‘weightlessness’. We talked about how your perception of your weight comes from the force supporting you, not from the force of gravity on you. We talked elevators, and then a student asked about space, so we talked about free fall in orbit, which is actually a look-ahead and  not going to be on the final, but they were super fascinated and I was hyped up on half a cup of coffee and super love space, so we talked about space instead of tides. Woops. My colleague is a big surfer, so he’s super into tides, which means his classes go into that topic much more deeply. I think they’re neat, but I’m way super more into space, so I like talking about space stuff. The kids are learning science. That’s the important bit.

Honors Physics: Gave them the applicable AP Physics 1 problems from the last three years with the caveat that they are very challenging, but if they can do these problems it will help them process the information better conceptually. I think the AP1 problems are fun physics puzzles, but I appreciate that they were more reasonable this past year than the first two. I even got confused about the 2017Q2, because I didn’t see the “rod is much more massive than the disk” and was trying to explain how when a disk sticks to a rod it changes the I, but in this case it doesn’t because of the relative masses and EVERYONE GOT CONFUSED. Super duper my bad.

And then a student asked me another question that ended up turning into us trying to figure out on the board together what would ratio of masses need to be to get the same final omega for a disk hitting a rod at the end of it (distance L) compared to another mass hitting somewhere else on the rod (ultimately figured as cL where c < 1) if they had the same initial velocity. After filling and erasing three boards full of trying stuff and false starts, we ended up with this:


I don’t like it. It doesn’t make sense to me how this result constraints L, as if you can only have a rod of a certain length for physics things to happen. Anyone have any insight? I’m guessing I made a fundamental mistake somewhere, but it’s not jumping out at me right now.

AP Physics: Gave half the class 2016 and and the other half 2017 APC FR questions, had them work on it and then teach each other. The first did not take the teaching each other seriously at all, so I had them go back to working separately. The second class started teaching each other before I even had to say anything. Good job, kiddos. You learn that physics. AND THEN TEACH IT!

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