# Fall 2016 Mechanics Week 10

This week, we review a little and also study the final topic: How torque is the rate of change of angular momentum, and how they are both vectors, so when torque is perpendicular to angular momentum, torque doesn’t increase or decrease angular momentum. Instead, torque causes the angular momentum to change direction. This is precession.

For Tuesday,

first hour, we review a little to get back in shape from the week gone by. Be ready to finish your projects.

Before Class

• After our discussion last Thursday of how to motivate and apply a lens, I decided to write a small chapter on how to do this after 2.3 vectors. Please read it and consider if this would have been a good idea to assign in the second or third week of classes: 2.3 Z Lens Motivation and Application
• Please review Statics Video – but this is optional. It’s not assigned.

During Class
Make some time to discussion projects.

second hour, We look at angular momentum as stability.

Before Class

• See video on Inclined Plane using Only Energy (no kinematics at all!) (3.5 minutes)
• See Veritassium video on how angular momentum provides increased stability against rotation.
• Please check out PS #9, Due next Tuesday in class,

In Class

• Angular momentum and Gyroscopic stability. We have some cool demos for this.
• Why must we spin frisbees or footballs to make them fly stable? What is counter steering on a motorcycle?
• Hand in PS #8. Work on some of the questions together.

After Class
Post Video Project tonight
Do some midtern #2 from years past – they cover the 2-D work we are doing just this last two weeks.

Thursday
first hour, we explore precession.

• Here is a precession video I made recently to explain precession.
• Please see Precession by Veritassium , a super professionally made video. You’ll let me know if it’s more helpful than my video.
• Optional: Here is an old precession video I made a few years ago. It’s long and slow with lousy graphics, but it has over 3000 views, so some people found it helpful: Pete’s OLD Precession Video

During Class
Explore precession with a special activity borrowed from mechanical engineering

second hour

Before Class

During Class

• Big Exam! #7

After Class

• Make sure video project is posted tonight