# Week 14

**Read:**Planetary motion (ASGv2 Chap. 26), Universal Gravitation (ASGv2 Chap. 27), Hypothesis and Natural Theology (ASGv2 Chap. 28).

**Key topics:**Kepler's laws of motion, Newton's universal law of gravitation, natural theology, scientific apologetics, and Newton's argument from design.

**Homework:**

- Phases of the moon (Ex. 26.1),
- Phases of venus (Ex. 26.2),
- Acceleration and the force of gravity (Ex. 27.1),
__Meteor problem:____Mass of Jupiter:__Io, a small moon of Jupiter, has an orbital period of 1.77 days and an orbital radius of 4.22 x 10^5 km. From this data, determine the mass of Jupiter. (Video solution)- Steel, silk and gravity (Ex. 27.3)
**,** - PHY 201: Pulley problem: A 10 kg mass is suspended from a thin string. The string is wrapped a bunch of times around a solid disk that acts as a pulley. The disk/pulley has a mass of 2 kg and a diameter of 5 cm. The mass is released from rest and so it begins to descend due to its weight. As it does so, the string, which is wrapped around the disk, causes the disk to rotate (the string does not slip). Note: here is a video solution.
- How much torque does the 10 kg mass exert on the disk?
- What is the angular acceleration of the pulley as the 10 kg mass falls? Is it constant?
- What is the angular velocity of the pulley? Is it constant, or time dependent?
- The floor is 3 meters beneath the release point of the 10 kg mass. How long does it take to hit the floor?
- What is the speed of the mass just before it hits the floor?

**Lab:**Centripetal Force Laboratory (Ex. 24.4). See laboratory videos below!

**Centripetal Force Laboratory (4 videos)**

Chapter 26 (4 videos)

Chapter 26 (4 videos)

**Chapter 27 (6 videos)**

**Chapter 28 (1 video)**