Week 7

Monday: Holiday!


Before Class

  • Hopefully, you’ve sent me your empathy self intervention by Monday, if not, please send it before class.
  • Please Watch Bucket of Water over your Head,
  • Please read 5.3 Loop the Loop: Circular motion in the vertical plane that you can find in our textbook. Please make sure you try Exercises 3,4 and 5.
  • Please Watch Skateboarding Loop of Death
  • Be prepared to address the question, “when I stand on the scale on the equator and on the North Pole, where do I weigh more?” Will you follow the dynamics protocol, will you make a FBD?
  • 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.
  • Finish PS #6
  • I posted solutions to assessment #6. They may be helpful for some of PS #8… but look at them anyway please.

During Class

  • Be prepared to address the question, “when I stand on the scale on the equator and on the North Pole, where do I weigh more?”

Next, 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.


Before Class

  • PS#7 posted on main class website
  • Read 6.0 Systems of masses.
  • Solutions posted on main class website for PS#6.
  • 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.
  • SO! about “where you weigh more?”. A few students were wanting to see this slide longer, so I’m providing it… It provides a way to get the answer… but this is just “the protocol” that we learn and practice for dynamics questions.
  • Slide for where we weigh more

During Class

  • Looking at some physics systems
  • Assessment #7


Thursday we look at a rotational system

During Class

  • A day at the races, racing rolling downhill!