Week 8 121 W2020

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

Before Class

  • Finish PS#7
  • If you didn’t watch it for Thursday because the link took you to the other assigned video again, please now watch Rotational Systems
  • 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.
  • Please watch this review video of rotation: Big picture rotation! You will notice two references to precession (that we haven’t covered yet) from 5:11 – 6:00 and and from 9:08 – 9:24 that you may find interesting, but you are not responsible for until next week. Likely, we’ll revisit this video at the end of the quarter, but it’s also a very good review right now. You’ll have to tell me during class if this review was a good idea, and if I should remake it without references to precession, or if this preparation is fine.
  • 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.
  • If you haven’t, please finish your project and submit it for the second evaluation.

In Class

  • Discuss project #2


Before class

Wednesday: 2D mechanics (no trig).
We have done linear mechanics in a straight line and rotational mechanics. Now we will introduce components, angles, and trigonometry and spend the last 3 weeks reviewing the same curriculum with the inclusion of angles. This is a great opportunity to improve conceptual knowledge.

Before class

In Class

  • Shooting a cannon ball off a cliff and dropping one… which one hits the ground first?
  • What happens when you throw a ball straight upward, but you’re in a train that is moving along at a constant velocity?
  • Practice Components


  • See the video on 2D Components of Force
  • See the video on 2D work (5 minutes)
  • Please read 7.1 in your textbook
  • Please see this video of 2D momentum
  • Take a look at this NPR article about the effect that empathy can have on society. Would you have been able to respond the way Patton did? We’ll talk about this in class.
  • Some people have asked me what classes I have next quarter. The only classes I facilitate are intro mechanics (the one you’re in) and three classes dedicated to sustainability/energy/poverty mitigation. Fall: PSC-391 Area D-5, “Appropriate Technology for the World’s People, Design”
    Winter: PSC-320 Area F, Energy, Society, and the Environment, and
    SPRING!!: PSC-392 (PSC-391 is NOT a prerequisite) Area F. “Appropriate Technology for the World’s People, Design”. This is a group project oriented class where we learn about implementations of technology in impoverished communities. We design and build stuff. All technical levels are welcome. There are Childhood Development majors and Engineering majors. If you want the class and can’t register, let me know.

In Class

  • Talk about projects – Project proposal due by next Monday.

After Class

This week we continue exploring vector components and how we can decompose them into perpendicular components. We look at the Conical Pendulum… or Tetherball problem, and we look at how a point mass can have angular momentum.