121 Winter 2019 Week 8

Monday, Midterm #2
The midterm will cover everything we’ve done up until now, but will focus on material after MT#1. However, of course everything from before will be necessary to understand the more recent material.

Tuesday: 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
  • Discuss project #2


  • See the video on 2D work (5 minutes)
  • Please take this short Survey #7
  • Please read 7.1 in your textbook
  • Finish MT#2. Copy of exam with comments posted on main class website.
  • Read over your classmates empathy interventions. We will discuss in class.
  • 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.
  • Please have your MT#2 corrections for all 4 questions done for Thursday’s class. UPDATE! Here is what we (myself, Rachel, Owen, Matt) decided. I will grade your MT#2 corrections and average that grade with your original grade weighted 2:1 – that is, two parts the original grade and one part the improvements. You will be graded on all four problems. I will collect these in class tomorrow, Thursday. However, you are welcome to slide them under my door as late as midnight Friday night. Additionally, the LAs will be by my office on Friday from 10 AM – 2 PM to offer support.
  • PS#7 is posted on main class website. Please look through the problems.

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.


  • Please see this video of 2D momentum
  • Problem set #7 is posted on the main class website. Due Monday. Please get it started.
  • Finish your **perfect** MT#2
  • Please have your MT#2 corrections. To be clear, I will grade these corrections as an independent midterm for all 4 questions. Your final grade for MT#2 will be a weighted average of the original midterm and these corrections: 2:1 – that is, two parts the original grade and one part the improvements. As far as cheating, you are expected and encouraged to get any help to learn and understand how to solve this problem, but you must understand what it is that you hand in. In order to get full credit, please sign the following statement at the end of the exam (the exam with improved wording is posted for your convenience on the main class website):”By signing below, I testify that I understand everything I wrote on this exam and could reproduce this work if asked to do the problem again.”

    If there is something in your work that you don’t understand, please either learn what it is you don’t understand, cross out the work that you don’t understand, or don’t sign the statement.

  • I will collect MT#2 corrections in class, but you can slide them under my door as late as midnight, Friday night.
  • For your assistance,  LAs will be by my office on Friday from 10 AM – 2 PM to offer support.
  • Check out the reflection from the empathy self intervention submitted during yesterday’s class.