Density of Earth

Earth's density is about 5.5 gram per cubic centimeter, which, compared to water (1.00 g/cm³) is pretty high -- Earth has a thick rocky crust and mantle above a metal core of iron and nickel, very dense.

This week's learning module is UP.

Your learning module for this week is now up. You can look for it in the light bulb folder on the course home page.

With this chapter on momentum, we begin the study of the concepts that will help us analyze and comprehend the gravitational tractor project, designed to protect Earth from asteroid impact... we hope!

Chapter 5 learning module is UP.

Last learning module for Exam 1 is now available in Webcourses. It is about universal gravitation.

There are links to two articles about theoretical spacecraft, and you can scan them now for gravitational concepts. The main import of the articles, however, will be in chapters 6 and 7 on momentum and energy.

Week 4 learning module is up!

As promised, your learning module for this week is up. It covers the concepts of Newton's Law of Universal Gravitation.

New mini-podcast about tides

I just created a new mini-podcast about tides. It works through questions 43-46 on p. 95, in the chapter about gravitation. It is available in iTunes U.

Learning Module 5 is ready now.

I suggest a day off from physical science brain work, but your next learning module is now ready: Universal Gravitation.

Too, I will probably set up our writing assignments this week, now that we have the basic tools, F = ma and so forth.

Just finished more Tw for space shuttle exercise

I just streamed a bunch of narration and a diagram related to exercise 10, p. 73, which asks about the relative strength of gravity for the space shuttle on orbit at 400 km altitude.

Diagram is to scale, big and nice, and might help you sort out a bunch of other gravitational questions. Go into the Tw stream and click on the link to Week 2 files.

Writing Assignment 0 is UP.

Writing assignment 0 is now ready for you to tackle. Look in the Week 2 learning module, item 8.

It might seem like a trivial task, but be careful, because all your other 48 writing points depend on your decision in this assignment! Think it over very carefully.

Due July 8, Wendesday, 11:59 PM.

Grading the SpaceShip Two discussion

I am grading the discussion posting, a few dozen at a time. Still 51 to go.

Meanwhile you can eyeball this graphic from the Scaled Composites company. They built SpaceShip One and sent it into space a few summers ago. The diagram shows the trajectory and so forth. Click it to view the full size image.

Some Flash files, pretty slick

I just activated some nice Flash simulation files, inside our learning module, Galileo and the laws of motion. Click on item 3.7, "Flash files for study" and you can try them out. They work nicely.

Also, there are some new blurb files about chapter 4 and chapter 5 exercises and concepts, in the same place, the Galileo learning module.

Ch. 5 mini-quiz is ready, as is a new exercise file.

The chapter 5 mini-quiz on gravitation is now available for you. It is due on Friday next week, back on the regular schedule.

Also, I created a new blurb file on the "Working it out" exercise on p. 81.

Two new mini-quizzes UP

I just activated mini-quizzes for chapters 5 and 6. Chapter 5 is the big one about gravitation.

First week to-do list

You can now click in to the PSC1121-0W62 area of Webcourses. Your objectives until Sunday evening are the following:

1. Work on the "First Week To-Do List" which is a small learning module, linked on the home page.
2. Get your textbooks.
3. STUDY AHEAD: Skim and eyeball the diagrams and figures in
   1. chapter 5 (gravitation),
   2. chapter 15 (waves), and
   3. chapter 20 (electromagnetism).