This is no longer the introductory unit for AP Physics 2, rather it is included in AP Physics 1! Which I think is for the best. It is a shorter unit, however based on my experience- and knowing how AP Physics 1 is- will be quite frustrating to students and teachers due to the lack of clarity of understanding of formulas. I remember getting desperate enough for understandable proof my first year teaching the course that I even looked in the textbook. The textbook has a small asterisk and a remark at the bottom of the page that said “A proof of Bernoulli’s formula is beyond the scope of this textbook.” So yah, a bit different from mechanics. I start the unit with a series of demonstrations, highlighting the properties of static fluids- then move through to them leading the demonstrations and teaching about dynamic fluids through simulations.
Introductory Demonstrations
At the beginning of the school year, I kick off the unit with engaging demonstrations that provide students with tangible reference points for later concepts. The introductory activity, which I humorously call "The Not-So-Basic Box," involves a cardboard box with holes on all sides. Using a Vernier gas pressure sensor, I demonstrate the uniformity of gas pressure in all directions.
The 1st demonstration is the bed of nails (it is the start of the school year after all, yay for fun). I was lucky enough to partner with our woodshop/engineering teacher to have students nail in over 5000 nails to create mine; it’s amazing. This captivating activity effectively clarifies the distinction between pressure and force, two concepts that often intermingle in students' minds.
The 2nd is the classic “upside down water cup.” I like to have a variety of cups and have students try variations on their own if you have sink access; laminated sheets or thin cardboard tends to work better than an index card. Students then solve for the force pushing upward using the air pressure from earlier to compare to the downward force of gravity; for the more advanced they can solve for the net force upward on the card.
The 3rd are the density bottles- i made mine with pony beads, black melting beads, and travel toiletry containers from Amazon. These bottles captivate students with their captivating behavior, while also exploring density as a concept. Utilizing demo kits, student projects, and the exploration of Cartesian divers, students gain insight into the world of hydraulics. If time permits, we conclude our exploration with a foil boat engineering challenge, a fitting introduction to the concept of buoyancy.
After the demonstrations above, I can go through this lecture quickly. It’s mostly a review of content they learned in the lecture, but with the formulas. The one point students do tend to confuse is gauge vs. total pressure. I find it easiest to introduce gauge pressure as a separate concept. Also, for practice on factors affecting buoyancy, some ranking tasks involving floating blocks- ranking by volume displace, buoyant force, etc.
Buoyancy lecture tends to be simple and straightforward- I like to do a live problem solving demonstration where they use the apparent weight of an object in and out of water to determine an object’s mass. I also really like showing the TEDed Videos on Archimede’s Principles (both of them!)
My favorite part of this lecture is the Bernoulli’s demonstrations- I give the students a list and assign them each a demonstration to learn how it works and create an infographic explaining it- then during the lecture students can choose to perform the demonstrations and teach the class rather than myself!
And now we are on moving fluids! As their homework prior to this lecture, students complete the pHet Fluid Flow simulation. Part 1 reinforces their prior knowledge, part 2 explores Bernoulli’s conceptually, and Part 3 is a little iffy- but ideally it teaches Toricelli’s! (student handout attached left). I also use a couple demonstration pieces to show how moving air lowers pressure.
