141 Fall 2019 Week 8

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.

Monday: No Classes At Poly


Tuesday, we look at how a point mass (radius = 0) can have angular momentum
Before Class

  • Please finish PS#8 with assessment #7 corrections
  • Hey, I left out one correct answer in the “2D Work” video: “For the dot product, you would multiply the displacement by the horizontal component of force.” I apologize for the omission. Additionally, in the last momentum question, if you want to find the final velocity of the car I hit, you’d need to divide p2 by m2. Also, if I am interested in finding out if the collision is elastic, YES I would find the kinetic energy before and after. If it is an elastic collision, then I would conserve kinetic energy.
  • See this video about the mass on the inclined plane (9.5 minutes)
  • Read 7.2
  • Watch Statics
  • Please look at some past student projects on the Project #2 website and think about your project. Emailing your instructor the group project is due before class Thursday. By posting your group project first, you reserve this topic for your group because I won’t allow two groups to do the same project. They have to be somewhat different. Reserve your project as soon as possible.
  • Have no idea of what to do for your second project? Consider doing question 1 in section 7.4. I think there’s still a carousel at Cuesta Park. Always be safe and DON’T be dumb and involve in any way anything with a motor/engine! I can also give you a scale you can use to measure forces you put on the wheel.
  • If you want to see the video of the bombs falling, please consider what it seems the land is doing, and watch until the bombs blow up. What do you notice?
  • Please read through the class’s Empathy Intervention statements, on the main class website under “feedback”. Please at least identify one entry where the author very nicely was able to place themselves into the shoes of the other person, and see the world through their eyes. Identify another entry where the author did not put themselves in the shoes of the other person. Then read your entry again and see how well you did with respect to the two authors you identified.

During Class

  • Project #2 discussion.
  • Inclined Plane
  • Hand in HW


Wednesday: we look at the conical pendulum
Before Class

During Class

  • Assessment
  • Practice conical pendulum
  • Practice slack lining?


Before Class

  • Please take this short Survey #8
  • Watch Slack Lining. Is this how you solved the problem?
  • Please see the video on angular momentum: Wheel Kick and Angular Momentum
  •  Veritassium Which Block Goes Higher?
  • Remember the demo we did with the “frictionless” cart that shot a ball straight up? The ball landed in the cart even if the cart had a constant velocity! Furthermore, we saw that the ball landed in the cart even when the track was inclined at a high angle. Now that we’ve done the inclined plane, please consider how to show that the ball should land back in the cart even if the cart is on an inclined track. Did you draw a picture? Pick a lens?
  • Hey, you know the guy who invented the “Beyond Burger” graduated from Cal Poly? He’s giving a talk tomorrow, Friday at 2:00 PM in Baker Science 180-114. See more in BeyondFlyer.

During Class