# Week 2

Read: The Coherence of Substances (ASGv2 Chap. 2), Archimedes' Principle and Falling Bodies (ASGv2 Chap. 3)

Key topics: Early modern ideas about the cohesion (internal binding forces) of substances; Archimedes' principle, the effect of buoyancy and drag on bodies falling in fluids.

PHY 201 lecture: Aristotle's wheel: an ancient geometrical problem related to atomism and infinitesimal calculus.
Quiz: Quiz covering week 1 material.

Homework:
1. Floating iceberg (Ex. 3.1),
2. The effect of buoyancy on a falling body: A pure indium ball having a diameter d = 1 cm is suspended from a tiny thread in a vacuum chamber. (a) What is the tension in the string? Hint: look up the density of indium (a soft metal). (b) If the ball is suspended in a vat of liquid gallium (instead of a vacuum), what is the tension in the string? Hint: look up the density of gallium. (c) If the thread is now snipped, what is the acceleration of the indium ball as it falls through the liquid gallium? Ignore drag (but not buoyancy) for now.
Lab: Archimedes' principle (Ex. 3.4) and Falling bodies (Ex. 3.5)

Chapter 2 (2 videos): In the following two videos, I discuss Galileo's attempt to measure how much nature "abhors a vacuum." He does this by measuring the force it takes to suspend a column of water in a cylindrical tube. You should watch these with the textbook in hand so you see how they relate to the text.

Chapter 2 (2 additional videos for PHY 201 folks): In the next two videos, Galileo wrestles with the novel concept of "atomism." In particular, he considers how matter might be comprised of innumerable infinitesimal pieces. Notice here that Galileo is dealing with topics that are related to calculus 50 years before Newton and Leibniz publish their famous work on calculus. In doing so, Galileo recalls the famous "rolling polygon" that was considered by Aristotle in the 4th century BC in his book Mechanics.

Chapter 2 (optional video): You can skip the following video if you want. Here is a brief summary. Galileo's character Simplicio believes that inanimate objects (like rocks) can act for purposes (or "ends"). Galileo's character Salviati, on the other hand, believes that inanimate objects cannot act for purposes (or "ends"). Simplicio and Salviati are presenting the famous conflict between ancient/medieval science (the via antiqua) and early modern science (the via moderna). According to ancient/medieval science, nature has final causes (things act for a goal or purpose); according to early modern science, nature does not have final causes (things do not act for a goal or purpose). Interestingly, science today has begun to look more like ancient/medieval science in some ways.

Chapter 3 (8 videos): These videos deal with Archimedes' principle and the effect of buoyancy on falling bodies. You should watch all of these.

Physics 1