PHY138Y - Mechanics - Class 7 - Mon. Oct. 3, 2005


"Newton was not the first of the age of reason. He was the last of the magicians, the last of the Babylonians and Sumerians, the last great mind which looked out on the visible and intellectual world with the same eyes as those who began to build our intellectual inheritance rather less than 10,000 years ago.”

John Maynard Keynes (1963)


First Written Homework

Each quarter will have one written homework assignment. It is to be solved as a group effort by the same teams that have been doing activities in tutorial. It is due Friday, October 14 by 5 PM in the "Drop Boxes" in the basement of the Burton tower of McLennan. Written homework assignment

Representative Assembly

Each tutorial group will choose a representative, and we will meet with all the representatives on:

Friday, October 14
3 - 4 PM
MP 222

We will discuss issues of organisation and communication in PHY138. We will not discuss physics.


Effective immediately do not use ROSI to change your lab section. Instead see Dr. Deyirmenjian in MP124.

Labs begin on Tuesday October 11 at 2PM with P0202. The first P0102 lab meets Tuesday October 11 at 6 PM; the next P0102 lab will meet on Monday October 24 at 2 PM.

The full lab schedule is available at

Today's Class

We finished Chapter 6. I did a small projectile example involving bullfrogs. I used a statement from §6.4 about Galilean relativity to re-inforce the fact that the laws of physics are only true in inertial reference frames; the remainder of this section is not examinable.

We then discussed §7.1 - §7.6, which nearly completed Chapter 7. We will begin next class with §7.7 - Nonuniform Circular Motion.

Flash Animations

Galileo's original argument supporting his principle of relativity. Flash animation of Galilean relativity
An animation of Student Workbook activity Chapter 6 #8: Tarzan swinging from a vine.
Illustrating the text's r-t-z coordinate system.

In-Class Questions

We asked this question about Tarzan swinging from a vine. The correct answer is 2. Initially about 60% of the class got the correct answer. After some in-class question, this did not change but the percentage choosing wrong answers changed.
  Before Discussion After Discusion
2 (correct)
We also asked this question about circular orbits. The correct answer is 2: the acceleration of the object is approximately g. About 90% of the class got this correct: well done!

Class Materials

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

Suggested Problems

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