I made this last weekend and I’m hoping there’s still time for other teachers to benefit from it this year. Here are links to the materials as a TL;DR:
In my AP Physics C course, I try to make sure my labs have a research question that represents something truly unknown to my students. Often this involves determining properties of a specific physical object that they can’t just look up, or assessing the level of validity for common physics-problem assumptions.
The question for my projectile lab is: Does the launch speed depend on the angle? I use a spring-powered launcher like many those that many science departments have. I ask students to determine the launch speed they get when firing horizontally and then compare that to the launch speed they get when firing at an upward angle. I typically introduce standard deviation here (many of my students have already seen it a little bit) to help them make a quantitative statement about how similar/different the two cases are. (I used to teach t-tests and use those in multiple labs, including this one, but after a few years I decided it wasn’t worth the time investment.) Students nearly always find that the horizontal shot leaves the launcher with a faster speed than the angled shot does, and then I ask them to hypothesize about why that might be. They all had Honors physics last year, so they usually come up with valid guesses.
Other than the angle used for the second set of launches, all the measurements for the lab are lengths. Ranges are measured by taping down a “target” sheet and using carbon paper to leave marks which show the landing spots. Students usually need an entire period (45 min) to get oriented and run through the procedure. But, since my school is 100% remote right now, we obviously couldn’t do that. So…
Taking some inspiration from Pivot Interactives and the homemade Pivot-like experiments I’ve seen other teachers making, I recorded videos and images of myself performing the lab which students can use to understand the procedure (even without any words!) and make measurements for themselves using the views I provided of the instruments. There are some areas of ambiguity in the “evidence” slides, most of which were deliberate and meant to get my students talking to each other about how to interpret things, as well as to ensure that the groups wouldn’t all get exactly the same results at the end.
There’s also a cute dog as my lab assistant! He loves fetch so he was pretty helpful. (Although wiping dog slobber off the ball between trials did slow me down a little.)
I ran this during a long, synchronous session. It took about 2.5 hours for most groups to do the measurements, algebra, calculations, and writeups. Overall I felt like it worked out OK. It allowed me to largely reproduce the experience my students usually get, including the chance to (mostly) make their own measurements without being handed canned data or running an idealized simulation. Students always love playing with the launchers, though, and it’s sad that they miss out on one of the most-fun lab days. And, naturally, they lost the chance to tinker with the setup themselves and encounter all the little quirks of working with real equipment. Stuff like figuring out the best way to clamp their launcher down, how to mark a spot directly below the launch position, that you need to prevent the ball from making extra bounces on the paper because they leave confusing extra marks… It’s safe to say I prefer the in-person version. But hey: at least this way nobody spreads a deadly disease.
Things I might do differently if starting from scratch:
- I had to improvise a bob for my plumb line, so I awkwardly hung one of the clamp’s handscrews on it. It looks weird/distracting in the first video, and then when I angled the launcher later I had to use something smaller anyway because it was bumping into stuff.
- I should have shown myself taping down the target sheet so students would know it was fixed in place.
- The box I used as a vertical reference line had my full address showing so I had to block it out in post… learning how to do that took me as long as almost everything else put together!
- When I first draw the reference line for my horizontal measurements the pen wasn’t writing well, so it’s hardly visible.
- The horizontal distance from the launch position to the edge of the target sheet came out as almost exactly 60 cm simply through chance. If I redid this–since it’s for my AP kids–I would take care to make this distance more awkward. (When choosing my launch angle I *did* deliberately pick one that wasn’t quiiiite on any of the lines.)
- I didn’t have a good table at home to clamp my launcher to, so it wasn’t very secure and ended up gradually rotating left throughout the experiment. Although this can be seen from the spots on the target sheet, I wish I’d either had a sturdier setup or thought to subtly draw student attention to it with another piece of evidence.
- Maybe find a pair of safety goggles for the dog??? Would make the experiment roughly 82% more adorable.