# Week 2

**Read:**Archimedes' Principle and Falling Bodies (ASGv2 Chap. 3) and Falling Bodies and Pendular Motion (ASGv2 Chap. 4).

**Key topics:**Archimedes' principle, the effect of buoyancy and drag on bodies falling in fluids, pendular and periodic motion.

**Homework:**

- Floating iceberg (Ex. 3.1),
__The effect of buoyancy on a falling bod____y:__A pure indium ball having a diameter d = 1 cm is suspended from a tiny thread in a vacuum chamber.

- What is the tension in the string? Hint: look up the density of indium (a soft metal).
- 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.
- 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.

- PHY 201 problem:
__The effect of drag on a falling body____:__

- What is the terminal velocity of the ball? Hint: at terminal velocity, the acceleration is zero. Let's assume that the flow around the ball is turbulent, so that the drag force is given by D = 1/2 * (fluid density) * (cross sectional area of sphere) * (drag coefficient of sphere) * v^2. The drag coefficient of a sphere is approximately 1.
- Now: repeat this problem for indium ball if it is submerged in liquid mercury (instead of liquid gallium). In particular: what is its terminal velocity? Does the indium ball ascend or descend?

- Falling gold balls (Ex. 3.2),
- Sinking ball of wax (Ex. 3.3),
- Ivory balls (Ex. 4.1),
- Comparing pendulums (Ex. 4.2),

**Lab:**Archimedes' principle (Ex. 3.4) and Falling bodies (Ex. 3.5)

**Chapter 3 (8 videos):**

**Chapter 4 (4 videos):**