Day 1: HEY! might not be a bad idea to start reviewing old problem sets and exams to prepare for the final exam!
Conserving Angular Momentum, when Sum of the Torque = zero
- Angular momentum = I*alpha, kind of like linear momentum = m*v
- Torque SOMETIMES = I * alpha, as stated above in rotational dynamics. Torque ALWAYS = rate of change of angular momentum
- For instance if Torque = zero, then angular momentum is conserved (just like we conserve momentum if there’s no outside force) it doesn’t mean that alpha = zero, like acceleration = 0 if the sum of the forces = 0, Think of the spinning skater pulling in her arms, yielding a positive angular acceleration.
Before Class
- Collect PS #7,
- PS#8 is posted please read through it.
- Read 10.5 in your text and check out example 10.14
- Please watch this video on torque = time derivative of angular momentum
- Please see video on Coriolis Effect , made by students from Fall, 2014
- PS#9 due next week has been posted. Please take a look at it.
- I posted my summary and reflection from your week 8 feedback on the main webpage
In Class:
Day 2:
How can a point mass (with no radius and no moment of inertia) have angular momentum? It all depends on the impact parameter!!
Before Class
- Angular Momentum of a Point Mass
- Bullet Hits Block Veritassium
- Please read through PS#8
- Solutions to MT#2 posted on main website. Please make sure as soon as possible that you would get all these problems correct if you were to encounter them again.
In Class
After Class
Day 3: More on how Torque = rate of change of angular momentum
Before Class
- Please see the video on angular momentum: Wheel Kick and Figure Skating
- Veritassium Which Block Goes Higher?
In Class
- Big Exam #6 – Solutions posted on main class page
After Class
Day 4:
Precession:
Torque is rate of change of angular momentum so dL = (torque)*dt. However, angular momentum is a vector, so you also need torque to change the direction of angular momentum.
Before Class
- Please see Precession by Veritassium
- read 10.8 in your text about precession.
- Optional: I made this video on precession. It’s long and slow, but it has 2700 views, so some people find it helpful: Pete’s Precession Video
- Rotational Big Picture
- Explanation of Veritassium Bullet Problem
- See solutions for BE#7
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?
- How is this related to precession?
Friday. You have until midnight tonight to post your link on the website for full credit.