141 Fall 2019 Week 6

THIS WEEK! Self Intervention on Empathy

Many of you know that I have a split focus at Cal Poly: Intro Physics and Sustainability/Energy/Global Poverty. The second focus involves my research and two classes that I introduced in 2007: Appropriate Technology, Development, and Appropriate Technology, Design. In these classes addressing our place with respect to global poverty, we have three “self interventions” whereby we change something about our lives and log the experience. If you like, you can read about the “don’t throw anything away for a week” self intervention. However, we as a class are going to take part in the “Empathy Self Intervention“. 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? Log the entire experience on the dedicated website. 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.


Monday – Flu Shots, free for students any time at the health center!
Before Class

  • Please finish PS #6
  • PS#5 solutions posted… sorry they are late.
  • Please read through PS#7
  • Please Watch Universal Gravitational Potential Energy
  • Please read 5.4 Gravitational Potential Wells, and Escape Speed that you can find in our textbook.
  • Please Watch Universal Potential Energy Graph. this is short and I think you’ll like it.
  • Be ready to answer the question that has changed peoples’ lives!:, “when I stand on the scale on the equator and on the North Pole, where do I weigh more?” Look… you don’t have to believe me – solve it with and without a Free Body Diagram (FBD) and you tell me if a FBD makes a difference.
  • Just if you’re interested: Here is a Veritassium Video explaining the neutron star collision detected by gravity waves, gamma ray bursts, and optical telescopes.

During Class**

  • where do you weigh more?
  • Be prepared to find escape velocity!

This week, we look at systems of masses, like two masses tied together and a single mass that is both moving and rotating – with both linear and rotational kinetic energy. We can solve these problems with a dynamics lens as individual masses (resulting in linear equations), or as a system of masses where forces act on the system. However, I find the easiest way to look at them is through an energy lens. How does the system’s energy change? You decide what’s best for you.

Please experience your empathy self intervention sometime this week and log your experience on the Empathy Self Intervention website. Add your post to the top. The user name is “interventor” with a small “i”, and the password is “Intervention” with a capital “I”. Please do this between the end of class today, Tuesday and next Monday.
>Before Class

  • Solutions for PS#6 posted. Please have a look.
  • Read 6.0 Systems of masses that you can find in our textbook.
  • Watch an introduction to simple systems This is an important video to understand systems.
  • Please check out the standard process for solving the system with simultaneous dynamics equations, one equation for each mass: Atwood Machine by individual masses. I won’t spend any more time on this method, but you are welcome to use it if you like.
  • Then see the video about how to solve the A System of Masses Using EnergyWOW, I watched the video myself and … it’s really fast. Please remember that I condense these discussions as much as possible. They are meant to be stopped every few seconds so you can take notes on the video or just think about what was said.
  • Start your Empathy Self-Intervention after class Tuesday. Please feel free to go to the website to look at past students’ postings. There’s a few things I want to add because I recognize that this may seem rather outside the scope of our studies.  My appropriate technology classes have done these self interventions for years. It seems strange to many of students in the beginning. By the end of the quarter, many students claim that these self interventions are the highlight of the class. In fact, several students started a self intervention club. In past 141 classes, students expressed appreciation for the statement about universally using lenses in order to recognize that our knowledge is not complete. You’ll have to let me know what you think of the activity at the end of the quarter.

During Class

  • Looking at some physics systems
  • Hand in PS#6 if you forgot Monday… I should have reminded you!
  • Big Exam #5


Wednesday we look at a rotational system

Between yesterday’s question “where do you ‘weight’ more – equator or north pole?” and today’s “how do you win a Tub-O-War?” what’s coming to me is student resistance to bust forward with a method until they have a plan toward the solution. Again, I’m asking you to go forward with a plan before you have a plan to the solution. Sometimes we can’t see a plan until we’ve explored it – like needing to walk down a path for a while before knowing where it will bring you. Please try to notice this resistance, and make a point of doing something without knowing if it will work. Generally, so much in life requires that you risk wasting your time on something that doesn’t work. If you’re curious about me, you could read about some of the failures I’ve had that have brought my life value and allowed me to move in a direction I wouldn’t have known about: Guateca, or My Home.

During Class

  • A day at the races, racing rolling downhill!


We look at the parallel axis theorem and consider how it can make a problem easier to solve.

Before Class

  • I’m embarrassed to report that I looked at the solutions for PS#6 and noticed that the loop-de-loop problem was done very poorly… actually referring to a “centripetal force”… which we know is a fictional creation. I made a new solution for this problem. Please see it on the **newly posted** PS#6 solution.
  • I think the most effective way to learn is to work in groups with other students. If for some reason, this isn’t working, consider trying out the free tutors provided by Cal Poly Physics Department. Link to the learning center is on the main class website.
  • Watch Parallel Axis Theorem
  • Please read 6.2 Center of Mass, this is important, and there’s no video on it, so I recommend you read this short section.
  • Please read 6.3 Parallel Axis Theorem
  • Please take this short Survey #6
  • Does a feather really fall the same as a bowling ball in a vacuum? See Human Universe do it.