# PHY138 - Mechanics - Class 5 - Monday, September 26, 2005

## Introduction

"Nature and nature's laws lay hid in night;
God said 'Let Newton be' and all was light."

Alexander Pope, epitaph for Newton

## Announcements

• MP Problem Set Chapts 1 - 4 due today by 5PM. This is an extension because of problems with Rogers and MP.
• MP Problem Set Chapts 5 -6 due by Friday September 30 by 5PM.
• Pre-Class Quiz Chapts 7 - 8 is now available. It is due Monday, October 3 by 10 AM.
• The "division of labor" in PHY138 means that:
• Dr. Savaria does all administrative things.
• I do the physics of this quarter

## Suggested Problems

As already discussed in the summary for Class 3, doing problems is an excellent way to learn physics, and the more the better. I am suggesting some extra problems from the textbook; my suggestions are available via these class summaries. I choose problems that I like for one reason or another, and don't pay any attention to whether they are odd numbered or even numbered. Answers to odd numbered problems are in the text, and your tutor has the answers to the even numbered ones.

We can not afford to produce detailed solutions for these problems, which we would have to pay someone to do. Sorry.

## Video Available

 In class on Wednesday, we did a demonstration of falling dominos. A short video of the demo is available via the button to the right; it will appear in a separate window.

## Today's Class

We finished Chapter 4 and came within a hair of finishing Chapter 5.

## About Studying, Especially Studying Physics

 In class today, we discussed effective study techniques. A one-page document of that discussion is available by clicking on the blue button; it is in pdf and will appear in a separate window.

## In-Class Questions

 We asked this question about dynamic equilibrium. The correct answer is 2. Only about 30% of the class go this question correct at first.

We then had the class break up into small groups to discuss the question. After this discussion, the number who got the question correct went up dramatically. Here are some rough percentages:

1
10%
8%
2 (correct)
30%
90%
3
0
0
4
60%
0
5
0
2%

 We also asked this question about the difference between gravity and acceleration. We will discuss the answer in the next class.