# 121 Spring 2018 Week 5

Tuesday:
Before Class

• I posted MT#1 on the main class website. I also posted another copy with some comments and direction. Please start your corrections/talking with friends about these questions.
• Problem Set #4 posted – Due on Thursday!. Please have a look at it and do the problems as you cover the material.
• See 4 Lenses of Rotational Motion Oh my, this video is way way too long. Please watch it in two sittings and take notes.
• Consider joining Engineers for a Sustainable World (even if you are not an engineer).
• * Please be aware of the 24-hour cool off policy: For 24 hours after you get your exam back, you can not ask me questions about it (and you can’t buy a gun). I want to collect perfect corrections for MT#1 on Thursday. So, please figure out what you might have missed and how to support a better understanding
• Please See Video: which includes the fundamentals of rotational dynamics and rotational kinetics.
• Watch the videos: Torque and the Lever
• Finish PS#4 if you can.
• Interested in going to Honduras during 2018 winter break to support the Global Medical Brigade?
• If you’re interested, please come to the bicycle breakfasts this month. Yes, FREE FOOD – just ride your bike there.

In Class

Working out with the “inertia wand”
Which Way does the tricycle move when I push on the pedal with an outside force? Will the outcome be the same as it was for the last class?
Not handing in PS #4

After Class

Thursday: Statics. and Conserving Angular Momentum, when Sum of the Torque = zero

Master the use dynamics (vector sum of the torques = I * alpha) just as you did for force and acceleration in linear motion
Augment your use of Work-Energy Theorem with rotational kinetic energy.

Before Class:

• Finish PS#4
• Please read PS #5, due Monday, posted on main class website.
• Finish Project #1 for resubmission if you want to improve your grade.
• Read 4.6, introduction to statics.
• Then watch the video about the standard diving board problem
• Did you know that studies indicate texting costs students an average of half a letter grade in their classes. Should we do something about this? NPR story about cell phones and classes
• Please watch this video on torque = time derivative of angular momentum