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


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

Alexander Pope, epitaph for Newton


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. Video of the demo

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. About Studying document

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. dynamic equilibrium question

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:

Answer Before Discussion After Discussion
2 (correct)


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

Class Materials

Pdf version of the PowerPoint on the side screens. Theory of Intelligent Falling
Today's Journal. Theory of Intelligent Falling


Suggested Problems

previous class The arrows let you jump to the previous/next class summaries. next class summary