# Week 2 121 W2020

Monday

Before Class

– What if you want to see a video the second time and also want to see the questions? Just click on the small vertical bars at the bottom of the video that indicate where the questions are located in the video.

1. Finish PS #1. I dropped on long problem from this problem set and added the review of the assessment. The problem set looks very long. You will hopefully notice that we’ve done most of it in our class time.
2. Elon Musk just uses simple scaling to create disruptive technologies: Quartz Media Story

• 1.7 Forces, Momentum, Energy
• 1.8 Applying Lenses of Mechanics. Probably the MOST IMPORTANT SECTION. please read through and expect some kind of question related to conservation laws – what they are and what they’re not.

After Class:

Tuesday

1. View Pushing Box Problem..
2. View this 3 minute video : Energy, Work, and Power. Be prepared to answer this question: a 1000 kg car starts from rest and accelerates to 30 m/s in 5 seconds. Please calculate the average power the car produces to do this. Please put answer in Watts and Horsepower.
3. I posted solutions to Assessment #1 and PS#1, on main class website. It would be a good idea to know these problems for the assessment Wednesday.
4. View Scaling
5. Our final exam time is posted on the main class website on the timeline for “exam week”
• 1.9 Scaling – How do quantities and qualities change as things get bigger?
• 2.0 Forces and Work
• 2.1 Power
• 2.2 Units

During Class

After Class:

Wednesday:

We are going to graph some of our own motion, forces, energy, and power next week. In today’s videos, you will see several ways to extract kinematic data from a video. The full description of the project can be found on a link from the main class website.

Before Class:

1. Please view the video kinematic graphs, LIVE! and watch me draw graphs on a board to represent my motion on a bicycle.
2. View Smarter Every Day Grasshoppers, and try to repeat his experiment with the other grasshopper. You can download Tracker at this website. You may have an easy time doing this, or you may have great difficulty because of software compatibility. A past student wrote this to help: Tracker Video Instructions. Please work together. In the face of fighting with malicious software, you need good friends. All the same, if it doesn’t work for you, don’t sweat it, but please try to estimate the acceleration some other way, like using my Excel method in the graphing video I did below. You can even use the method we used for the water rocket. One student was able to get tracker to work on a Mac only after transforming the video into a .mov… here it is Grasshopper .mov
3. You can download Tracker from this website and use it! This is great for us because it means we don’t need to use university computers. Please try to do it yourself on your computers before tomorrow.
4. Do you have a good formula sheet for the assessment?
5. You will likely use Logger Pro (or Tracker) to analyze your motion data, so please see how we can collect our kinematic data using Logger Pro.
6. Please see how we can analyze our kinematic information from Logger Pro using Excel.
7. Readings: 2.3 Graphical Analysis of Kinematics
8. Read the description to project #1 on the main class website.
9. A number of students asked yesterday about the “finding the power output of the car” problem, “which speed do we use to find the power output?” There’s a number of ways to answer this question. The answer depends on which lens you use. Try “Power is the rate of change of energy.” You know the time and you can find the kinetic energy. Which speed will you use for finding the final kinetic energy?

During Class
Assessment #2, Prepare for activity next Tuesday

Thursday:

Before Class

We will explore more complicated dynamics problems.

Before Class

1. Two videos describing the role of vectors: Vectors: Forces, momentum, and Vectors: Energy and Kinematics
2. See video on
3. PS#2 is posted on main class website. Please read it and consider it, start a few questions.
4. I graphed my motion without Tracker. Please view: Graphing running. Some people had difficulty loading this video from PlayPosit. If this is the case for you, please just watch the YouTube source video.
5. Read section 2.4 (Vectors and Direction)
6. Have you ever played the “rope pulling on a stump” game? Why can’t you just pull the other person off the stump? What happens to you if you pull really hard? Which lens are you using?
7. Have your project planned out.