Teaching rotation as a cumulative mechanics review in AP Physics 1 or C

Where do you start with AP Physics 1 (or C) rotation, especially in a Pandemic Year when you might have a lot of virtual students?

Think of rotation as a vehicle for review-in-context of mechanics concepts.  Your class has studied the three main mechanics approaches:

• Forces/kinematics, where we start with a free body diagram and/or a kinematics chart
• Impulse/momentum, where we write the impulse-momentum theorem or p conservation
• Energy, where we start with an annotated energy bar chart

The whole point of the rotation unit, to me, anyway, is to give students a new context in which they can review these three main approaches.  The AP Live videos in 2020 started with a focus on rotation, precisely because rotation is a great way to start a cumulative review.

So what do I do for each of these topics in rotation?

I personally don't do anything significant in class on rotational kinematics, since this is such a straightforward extension of linear kinematics.  I ask a few released AP multiple choice questions dealing with rotational kinematics graphs, and demonstrate the solution with the PASCO rotary motion probe. That's it.  

For newton's second law for rotation, I use the rotating platform and an in-class problem set.  By changing the lever arm for torque, the force for torque, or the rotational inertia, students predict how the angular acceleration changes.  This is essentially word-for-word what I did in the AP Live Newton's Second Law for rotation video, except as a come-and-show-me activity where they check their prediction in the back of the lab with the rotating platform.  This year, since we were 100% virtual in February, I just showed the linked video to the class over zoom.*

*Short rant: you've gotta watch the video with the class.  You can't just assign the video as homework.  How do I know?  I tried assigning some short - 8 minute! - AP Daily videos earlier this year via AP Classroom.  In class, it became apparent that very few had watched carefully.  Sure enough, the stats from AP Classroom showed that only about a third of my class had even opened the videos.  This in a class where I get better than 95% completion for daily problem sets!  The moral I drew was, don't ask students to watch videos on their own, 'cause that way madness lies.

For angular momentum and rotational kinetic energy, I use Pivot Interactives.  I've sometimes spent a full week on the "marble collides with block and can" activity, without much preamble beyond the fact sheet and 15 minutes showing demos about what rotational inertia and torque mean.  In the video, just asking "is linear momentum conserved?" gets students to think about center of mass motion and reviews linear momentum; then "is angular momentum conserved?" teaches them how to deal with angular momentum (especially for a point object) better than any lecture.  And finally, "is mechanical energy conserved?" forces them to draw an energy bar chart and include rotation.  I mean, truly, this is all I do to intro rotation.  We get straight into problem solving with rotational kinematics and N2L for rotation.  They don't need any presentation, because they already know the concepts and simply apply them.  

As you can see, most of this rotation introduction can be done virtually.  In my classroom after spring break - that's March 24 this year - I have students just doing independent lab work.  We do quizzes and short problem solving homework assignments that help not only review but also help teach rotation.  But that's it.  Between the AP live videos, Pivot Interactives, and some very open-ended lab work, my students get all the resources they need.  At this point, the class is full of experienced physics students.  They do well learning rotation sorta on their own, as I guide them to use rotation as a means to overall AP Physics 1 content and skill review.