141 Fall 2019 Week 3

Monday : Springs 
Before Class

  • I posted your feedback statements on the main class webpage. Please take a look at what’s going on for you and your colleagues. In particular, I can tell you that this is the lowest point for many people… like culture shock has set in. A lot of people express concern about not knowing exactly what form to cast their answers in on an assessment. This is not a concern later in the quarter. You will all get this.
  • Before the assessment tomorrow, it would be a good idea to read again section 1.8 to improve your process – but you will update this with section 2.8. Additionally, I’ve added a short supplement for 1.8 that you can find on the textbook link, but I provide here as well:
  • Project #1 is due Wednesday. The requirements are clearly defined on the “first project description” page linked on the main class website.
  • Work on your project! It is due Wednesday.
  • See video about: Springs!
  • Potential Energy Graphs video
  • Read 2.6 Springs
  • Read 2.7 Energy Graphs
  • Read 2.8, a review about the lens method, updated to include the newly-covered vectors

During Class

  • a string breaks.
  • Hand in PS#3

Tuesday: Assessment #3

Before Class

  • Hey, so just so you know. I continuously update the textbook as we go along and get more ideas.  just realized that I hadn’t posted the updates. So, I updated it Monday morning. Consequently, you will find that for chapter 1 and chapter 2 only, your hard copy is not the most up to date version. You can see that on the website… but the differences are small.
  • Study for the assessment by looking at old midterm exams from classes past? See links on main class website to past classes.
  • See: Elastic Collisions with Walter Lewin at MIT
  • Read 3.0, Changing Reference frames and only then, see the video below.
  • Please see: Elastic Collisions with Pete at Cal Poly by Changing Reference Frames This is my most popular video – after ~ 7 years, it has over 30,000 views. See if you can tell me why it’s the most popular of my videos.
  • Read 3.1, elastic collision in 1 dimension.
  • If you like, please check out 8.4 from the original OpenStax textbook to see how the rest of the world looks at elastic collisions in 1-Dimension using simultaneous equations and a healthy amount of algebra..
  • Optional reading on NPR about active learning in Physics Education Research. The author, Carl Weiman who won the Nobel Prize in Physics for Bose Einstein Condensation gave a talk at Cal Poly some 12 years ago calling on us to evaluate and innovate teaching with the same scientific process we use for other scientific research. Since then, he’s become prominent in Physics Education Research. He’s published a considerable amount about active learning strategies and over the years has become more outspoken about the futility of the lecture model and need to change.
  • Another NPR article about education:
    • “The first step is to teach Socratically, by asking questions and having students think out loud. This works much better than lecturing.”
    • “Teachers who find their kids’ ideas fascinating are just better teachers than teachers who find the subject matter fascinating,”
  • By now, you should be very comfortable with the four lenses… what to look for, and how to “motivate them”… for instance, “I will look through an energy lens (identification) because the spring potential energy is converted to kinetic energy (motivating).” If you are not, please refer to chapters 1.8 or 2.8 until you are…. THIS is what you should have for your test notes if you’re not comfortable. Formula are of no use until you’ve identified and motivated a lens.

During Class

Assessment #3
Elastic Collisions


Wednesday 

During Class

Ballistics Pendulum

 

Thursday Friction!

Before Class

  • PS #4 has been updated to include two more questions.
  • Important to consider for today’s class… your life may depend on it! There’s a fire in the hall next to your room. You have two balls of equal size and mass to throw against a door in order to close the door with the impact of the collision. One is an elastic ball and one is inelastic. Which one do you use?
  • View Big Picture of Mechanics to get an overview of the first 4 weeks of mechanics.
  • Read section 3.2 about friction in your textbook. If you want to know more about the molecular nature of friction and biomedical consequences, please see this OpenStax description.
  • Please see the video I made for you guys about dragsters and friction. 
  • Some physical work I did at home

During Class

Escaping Fire in your Dorm Room