DL-Rotational Mechanics

Demo - Basic Quantities - I show angular displacement, velocity, and acceleration.

Demo - Moment of Inertia.  Two objects that have the same mass, but very different moments of inertia.

Demo - Solid cylinder vs. Thin Ring racing down an incline.  The cylinder gets there first, as it has a smaller moment of inertia.  

Demo - TP Moment of Inertia - Two rolls of toilet paper - one nearly full, one nearly empty.  Tug quickly on them to break off a piece of paper.

Demo - Equal and opposite torque - When you revv a drill, the motor spins one way, and the body of the drill counter-rotates.  Dirt bikes do this too - you can find a video here: https://youtu.be/kWZ3j2DXi7Q?si=qOT4UrUK7sse2ef5&t=25

notice the bike kicks right or CW.

Demo - Conservation of Angular Momentum.  I use the rotating platform, bicycle wheel, and mini weights to demonstrate the parallels between linear and angular momentum.  Also the differences.  I like to point out people's arm motions when they lose their balance, or when they are cliff jumping.

Demo - Hanging Gyroscope - I hang the spinning bicycle wheel from the ceiling and it stays upright.

Demo - Gyroscopic Stability.  I have an army surplus gyro with ball bearings, and I spin it up to show how it maintains its orientation.

Demo - Gyroscopic Precession - I hang the big gyro from the ceiling and with the angular momentum vector pointing away from the side tied to the rope, we use the right hand rule for (radius) X (Force) and show that the gyro precesses in the correct direction.  You can also just use simple linear momentum to explain the direction of precession.

Lab - Ezekiel's Wheel.  Students solve for the moment of inertia of the demo wheel using energy and dynamics

Here is the website: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/rotational-mechanics/ezekiels-wheel

The Charioteers: https://youtu.be/7f69SLJPNRU?si=6lGIPQeve0Eas92D

"There's a star in the east and a star in the west..."

Lab - Gyroscope  Lab.  A very lame lab, but fun.  Basically an excuse to play with Gyroscopes.  Students calculate the angular momentum of the gryoscope, and of the earth.  Sometimes if they make enough mistakes, the little gyro ends up with a higher angular momentum than the earth!

Lame Website: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/rotational-mechanics/gyroscope-investigation-lab

Lab - Conservation of Angular Momentum.  Students are given two models of how a mass on a string behaves when it is spinning, and you pull it in.  One is the Mandlbaur model where the velocity of the mass does not change.  RPMs increase only because of the change of pathlength.  The second model is that when you cut the radius in half, the speed doubles.  (This is what conservation of angular momentum predicts)

It's great fun, because in order to disprove the Mandlbaur model, the students need to calculate their uncertainty.

Check out the website: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/rotational-mechanics/ib-angular-momentum-lab

Also check out the dialog in the comments on this video:

https://www.youtube.com/watch?v=3JcF-H0u0Pw

I show the kids this - they think it is hilarious - but John Mandlbaur has proposed a hypothesis with testable predictions.

Demo - stuff

Lab - stuff