# Spring 16 Mechanics Week 2

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

Day 1: Hand in PS #1, PS #2 Posted on main webpage

STRIKE: Yes, it seems we will strike in week 3 and 4. Students have expressed an interest to know more about this so I have complied some about the strike. What will we do as a class? We’ll talk about it in class a little.

There is an interplay between the concepts of motion, energy, and momentum. We are learning how these relationships are affected by time (rates of change or time derivatives), and forces – how does a force change energy or momentum (how is momentum and energy conserved?).
Before Class:
1.View Forces Effect on p, v, E
2. View Big Picture of Mechanics
3. Read the introduction energy, and momentum:

• 7.2 Kinetic Energy and Work Energy Theorem
• 8.1 Linear Momentum and Force
• 8.3 Conservation of Momentum

Interested in Study Workshops?: Both workshops are every Tuesday and Thursday from now through dead week (except this Thursday due to the holiday). There are no workshops held during finals week. The earlier one is 6:10-7:30 pm and the later section is 7:40-9:00 pm. Both sections are always held in 20-128 (Engineering East). To sign up, please write Colin Webster at cgwebste@calpoly.edu

Day 2:
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 : 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.
• 7.7 Power
• Units 1.2. Remember how we should cancel units all the time. Please practice this every time you do a problem.

During Class

Day 3:
We are going to graph some of our own motion tomorrow. 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. I just added PS#2 to the main class webpage. Please take a look before class. You should find some of the questions to be familiar.

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. Ian was able to get tracker to work on his Mac only after he transformed the video into a .mov… here it is Grasshopper .mov
3. I graphed my motion without Tracker. Please view: Graphing running
4. See a video about how to measure power.
5. Also, see the video on hitting the golf ball.
6. Also, I’ve posted the solutions to PS#1 including the last problem.
7. Also, I posted answers, comments to Big Exam #1 on the main webpage.
• 2.8 Graphical Analysis of One-Dimensional Motion
• 7.8 Work, Energy, and Power in Humans

During Class

Day 4: Activity Day for First Project!

Before Class

1. Please view: Graphing a ball toss.
2. Please see how I solved the Grasshopper Problem Using Excel.
3. Plan your activity at Via Carta Bicycle Path.
4. Please see PS #2 on main webpage. I’ve updated a few questions.
5. See Big Exam #1 notes on main webpage.

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.
• If you have a laptop, please bring it, so we can start analyzing your work.
• I hope to hand back Big Exam 1. While your tests are better than the first Big Exam in previous classes, many students have yet to make the transition to prioritize communication over numerical answers. Additionally, I’m sure that many students may feel overwhelmed by the amount of information required on the test. I remind you that we started with all the concepts at once, so I do not expect that you will have them already mastered. However, I do have an expectation that you will have them mastered by week 4 when we have our first midterm. So Big Exam #1 should serve as a very good marker as to what you need to master in the next two weeks.

After Class
Analyze data, make graphs and calculations. Do PS#2 for Monday morning.