We are in the thick of midterm season and I imagine you are feeling a lot of pressure to keep everything going. Please remember that it is important to get a good night's rest and eat well before exams. If you need to prioritize your activities, make sure you keep mental health and well-being near the top of the list. Seek support from your networks and make healthy choices. You will be glad that you did and will also likely be more successful academically.

This week, are going to take part in the "Empathy Self Intervention" described in an assignment I posted due Monday, Feb 7. Recognize when you “otherize” someone – when you (erroneously) see them as completely not connected to you. Then do your best to cast the world through their eyes. What are they experiencing? What you think, what you feel, what you learn. Students often have a difficult time with this. Empathizing with someone doesn’t mean you agree with the other person, or think that they are right. It just means you try to see things as they do and experience what they are experiencing. You may ask what this has to do with physics... but doesn't it? As we learn to explore lenses, we may become more effective by reminding ourselves that our knowledge is not complete (as stated in the syllabus), and that it is beneficial to look at the world through other lenses. Please think about this and log the experience sometime this week starting Tuesday.

Learning Outcomes

By the end of this week you should be able to...

Apply the four lenses of rotational mechanics to spinning systems
Explain the differences between linear and rotational quantities
Calculate moment of inertia for various bodies
Analyze systems at rest by solving for the relevant forces and torques
Describe your thoughts and feelings as you imagine yourself in someone else's position after recognizing you have otherized them.

Day 17 | Monday 1/31 | Big Picture of Mechanics, Rotational Motion

This is our introduction to rotation. Please treat the videos as if they were a lecture. You have been taking notes as you watch them, just like a lecture, right? You could allow well over a half hour for them by stopping when you need to catch up. If something is unclear, write it down and please bring questions to class to ask your colleagues.

Goals:

By the end of the today you will be able to...

Describe the four lenses of rotational motion
Identify the direction of rotation using the right-hand rule
Describe the variables of rotational motion

Before Class:

PS#5: Problem Set #5 [T 2/1]: On Friday I added question #7, which you will likely recognize.
Video: Watch Four Rotational Concepts [6m0s]
Textbook: Read Ch 4.0 - Introduction to Rotation [2 pg, 2 ex]
Video: Watch Four Rotational Concepts - the sequel![6m41s]
Textbook: Read Ch 4.1 - Rotation Direction [1 pg, 1 ex]
Discussion: Please leave a statement and comment/question on our Week 5 Reading Discussion
Survey: Take this Short Survey - Day 17 [3 questions]
Reflect: Watch this short video about the happy and sad balls. Should you use an elastic or inelastic ball to close the door...in a fire?
I wrote an Email to you all last night indicating my expectation that you come to class today:

"I’m writing to let you know that our 141 class is an in-person class and is not a hybrid (in person/Zoom) class. I have (and may continue to) opened Zoom sessions for people that are in quarantine and because I myself was exposed (but tested negative). People who Zoom in recognize that this is second best, and see that I am not able to accommodate the people on Zoom with everything that makes this class successful. Additionally, I’m only willing to allow 1 assessment to be taken over Zoom. Beyond that, the final exam will substitute for a missed assessment.

Consequently, I do look forward to seeing everyone in class tomorrow (now today, Monday)."

During Class:

We will observe a spinning wheel and discuss its motion
We will practice identifying the direction of rotation
We will apply the lenses to rotational situations
We will discuss our short survey questions

Day 18 | Tuesday 2/1 | Moment of Inertia

The first video on connecting rotational and linear motion is short but has lots of information in it! Students have said this video is fast and confusing. Please stop many times and take notes. Bring your questions into class.

Goals:

By the end of today you will be able to...

Explain the motion of a wheel rolling without slipping
Calculate the work done and power supplied when a torque is applied to turn something
Explain why rotational inertia depends on the distribution of mass

Before Class:

Homework: Upload Problem Set #5 to Canvas before class.
Video: Watch Rotational Physics - units and correlation with linear physics [5m56s]
Textbook: Read Ch 4.2 - Connection Between Rotational and Linear Motion [2 pg, 2 ex]
Textbook: Read Ch 4.3 - Torque and Rotational Work and Power [2.5 pg, 5 ex]
Textbook: Read Ch 4.4 - Moment of Inertia [1.5 pg, 2 ex]
Discussion: Please leave a statement and comment/question on our Week 5 Reading Discussion
Video: Please see What is the moment of Inertia? [3min55s]

During Class:

We will look at the motion of a rolling wheel
We will examine situations where moment of inertia is important

Day 19 | Wednesday 2/2 | Torque and Lever Arm

The physics description of rotational concepts can be tough to wrap your head around but you have lots of intuitive experience with them. Where do you push on a door to open it? Why? Where do you hold a wrench when tightening or loosening a screw? Practice using the "fifth lens" - visual memory of personal experience - when solving problems to help assess whether your results make sense or not.

Goals:

By the end of today you will be able to...

Apply rotational dynamics to find angular acceleration
Augment your use of the Work-Energy theorem with rotational kinetic energy
Calculate moments of inertia for solid bodies using calculus

Before Class:

Video: Watch Moment of Inertia of a Solid Body [4m48s]
Video: Watch Torque and Lever Arm [6m4s]
Textbook: Read Ch 4.5 - Moments of Inertia for Solid Bodies [4.5 pg, 6 ex]
Discussion: Please leave a statement and comment/question on our Week 5 Reading Discussion
Study: We will have our weekly assessment in class. Review what you have learned so far and look at the Problem Set #5 solutions to see how to improve. Follow the problem-solving rubric to know what to expect.

During Class:

We will practice applying lenses to rotational systems
We will explore the moments of inertia of various bodies
We will take Weekly Assessment #5 [20 min]

Day 20 | Thursday 2/3 | Statics

We add a second condition to the requirements for equilibrium.

Goals:

By the end of today you will be able to...

Describe the conditions that are required to keep something immobile
Apply the conditions for static equilibrium to various situations
Choose an appropriate center of rotation for solving statics problems
Explain the importance of using our hands when we think

Before Class:

Hey, so it turns out that I made a mistake on the assessment... the carts run out of kinetic energy by the time they hit the spring, so the spring constant comes out to be zero.
Video: Watch Solving the Diving Board Problem [7m4s]
Textbook: Read Ch 4.6 - Introduction to Statics [2.5 pg, 2 ex]
Article: Read this NPR article on note-taking by hand (external)
Discussion: Please leave a statement and comment/question on our Week 5 Reading Discussion
Video: Watch Friction in Work Pushing a Foundation [8m31s]
Survey: Take this Short Survey - Day 20 [X questions]

During Class:

We will practice solving statics problems
We will discuss hands-on learning
We will review our short survey results

Week 5 Wrap-up

So what do you think of rotational mechanics so far? In a traditional class, this topic gets covered much later in the quarter. You are thinking about it now because hopefully you see how easily it fits into our parallel pedagogy curriculum. There are analogues between rotational and linear motion and similar relationships and concepts for each. Often, the tricky part is keeping track of the correct vector directions and applying the right-hand rule. Keep practicing and it will become more comfortable.

Next week we will review our empathy self-intervention logs and continue learning about rotational motion by exploring angular momentum, examining the universal law of gravitation, identifying what keeps objects moving in a circle, and investigating the mechanics of the loop-the-loop.

For now, take a moment to review our learning objectives for this week and grade yourself on your mastery of them. If you identify any that need more effort, review the videos and textbook or talk to a colleague for help.

Don't forget to submit your log for our Empathy Self-Intervention assignment before class on Monday.