F15 Mechanics Week 2

We will measure distance, speed, acceleration, momentum, force, energy, power.

Day 1:

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. View Scaling
  2. View Pushing Box Problem.
  3. View this 3 minute video that will likely help with question #4 on Problem Set 1: Energy, Work, and Power
  4. Read
    • 7.7 Power
    • Units 1.2. Remember how we should cancel units all the time. Please practice this every time you do a problem.
  5. Prepare problem set #1 (available on main class page). Come to class ready to hand in something to get feedback. Come with questions, difficulties, etc.

Day 2:
We are going to graph some of our own motion on tomorrow, Wednesday. I show you how I did it in #3 below. #2 is a super cool way to do it (in my opinion), but some students had difficulty getting the software to work.

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 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 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, please do your best to estimate the acceleration using my Excel method in the graphing video I did below.
  3. I graphed my motion without Tracker. Please view: Graphing running
  4. Readings:
    • 2.8 Graphical Analysis of One-Dimensional Motion
    • 7.8 Work, Energy, and Power in Humans
  5. Read over the grading rubric in the syllabus (available on main webpage) so you know how you’ll be graded.

During Class
Be prepared for a practice exam. We will have exams every Tuesday. Most of them won’t count toward your final grade and are there to practice the testing situation. Two of them will be midterms.

After Class
You should see the following videos that may help you for Wednesday’s activity:

    1. See a video about how to measure power.
    2. Please view: Graphing a ball toss.

Day 3: PS #2 posted on main page

Before Class

  1. See a video about how to measure power.
  2. Please view: Graphing a ball toss.
  3. Plan your activity at Via Carta Bicycle Path.

During Class

  • Meet at Via Carta!! Bring a cell phone or video camera. Bring something heavy to throw as high as you can and/or a beach ball, etc.
  • Bring your computer, so we can start analyzing your work.

After Class

Day 4: PS #2 posted on Main Pate
The vector sum of the Forces = mass * acceleration.

Before Class

  1. Please learn about Free Body Diagrams and Equal and Opposite Forces.
  2. Post Video about Vectors
  3. The Elevator Dynamics Problem
  4. Bozeman Science FBDs
  5. Do LON-CAPA “Week 2″… it’s due Monday, but please do it before class tomorrow if you can.
  6. Read chapter
    • 3.4-4.7 about dynamics

During Class

What is equilibrium? How do we find the resultant force? We introduce the “dynamics protocol” (Quiz on this tomorrow):
“The Protocol for Dynamics”:
0) Identify that this problem is about forces => It’s a dynamics problem
1) “oh shit, I don’t know anything”… there’s no formula for a dynamics problem!
2) “but I do know that (vector sum) F = ma”
3) I can draw a force (free body) diagram labeling all the forces at the point of action.
4) I can ask myself “is it in equilibrium?”
=> yes – then the sum of the forces is zero and the vectors must close on themselves
=> no – then I ask another very important question, “which way is it accelerating?” and know that the forces must add to be in the same direction as the acceleration.
5) Then show graphically how the force vectors add to provide a resultant force (the net force) in the same direction as the acceleration.