General College Physics

Wisconsin Lutheran High School

Week 14

Reading: PSE Chap 11, Rolling motion, angular momentum and torque

Topics: torque, rotational dynamics.

Lab:

Homework Problems:

Rotational inertia of triangle: Three 1 kg masses are fixed at the corners of an equilateral triangle. The sides have length 2 meters. If this triangular system rotates around the center of mass of the triangle, then what is its rotational inertia? Here is a video solution.
One mass suspended from pulley: 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?

Two masses suspended from pulley: Suppose that, like in the previous problem, the 10 kg mass is suspended from a string which is wrapped a bunch of times round the disk/pulley. But now suppose the other end of the string is attached to another (3 kg) mass suspended from the pulley. So as the 10 kg mass falls, the 3 kg mass rises. Repeat the previous problem. Here is a video solution.

Quiz: Monday Nov. 13. Covering rotational kinematics.

General College Physics

Return to course website.

Course syllabus

Physics: The world around us is in a state of constant change: the sun and moon rise and set, waves crash, mists rise, rain falls, fires burn, rocks form, and mountains crumble. Amidst all of these changes, there are certain patterns; there is a discernible order. In other words: the stars, the seas, the clouds, the rocks, and the earth itself each seem to have a particular nature. Physics is the careful study of the natures of things. In fact, the word physics literally means "natures" in the Greek language.

Course overview: General College Physics is a year-long introductory course for advanced (typically junior or senior level) students at Wisconsin Lutheran High School who want to better understand the natures of the things we see around us. It is a dual-credit course offered at Wisconsin Lutheran High School in collaboration with Wisconsin Lutheran College. For a detailed overview of the topics we will be covering, refer to the course website (www.greatphysics.com) and the tentative calendar on the following page. Emphasis on theoretical topics, careful thinking, laboratory experiments, and problem solving makes this course challenging. My aim is to help you succeed in this course, and to have fun while learning physics. So please do not hesitate to contact me with any problems you may run into this semester!

Advanced Placement credit: While this is not designated as an AP course, students students have successfully taken the AP Physics test at the end of the year for college credit.

Course textbook: The course will be organized around a book: the Pocket Guide to accompany Physics for Scientists and Engineers (4th edition) by Serway. (I’ll call this PSE for short.) I would highly recommend obtaining a copy of this book. It is inexpensive, compact, and well-written. It will make a very handy addition to your home science library. If you don't want to buy it, I will have copies to loan out for the semester.

Course time and location: The course meets every day (Monday through Friday) during the academic year from 2:16 until 3 pm in WLHS 223—in the science wing on the first floor of WLHS. On late start days (such as Wednesdays) the course begins at 2:24.

Professor: Dr. Kuehn from Wisconsin Lutheran College (WLC) is the professor for this course. Contact info: kerry.kuehn[at]wlhs.org

Teaching Assistant contact info: The Wednesday course sections (beginning in September) will be overseen by two teaching assistants. Alyssa Ebeling and Zeke Micheel are upper-level physics majors from Wisconsin Lutheran College. Here is their contact info: alyssa.ebeling[at]wlc.edu, ezekiel.micheel[at]wlc.edu

Course websites: In addition to the course information provided through WLHS’s OnCampus system, we will be also using a website I’ve designed for this course: www.greatphysics.com/WLHS1/

Homework exercises: I will assign weekly homework problems. These are designed to deepen your understanding of lecture material and to prepare you for the quizzes and tests. I do not intend to grade your homework solutions; I will merely give you credit for handing in your best attempt by the due date. Please refer to the late work policy for more details.

Laboratory exercises: Some of our weekly assignments will include laboratory work. Labs will typically take up at least two class periods. Your laboratory notebook pages must be submitted by the assigned due date. More details about the required format and expectations will be discussed before the first laboratory period. You will need to order/purchase a dedicated laboratory notebook. Here are guildlines on what to include in your laboratory notebook.

Quizzes: We will have in-class quizzes almost every week on Monday. To prepare for quizzes, you should read the assigned book chapter (at least once), review the lecture material, complete all of the homework problems, and review the homework solutions.

Tests: We will have a midterm exam before the end of the first (and third) quarters and a comprehensive final examination before the end of the second (and fourth) quarters.

Software: Logger Pro 3.15 Is an excellent data analysis software package. Download for Wndows 10, 8.1, 7, and for macOS 10.14, 10.13, 10.12, 10.11, 10.10. For more details on how to download and install Logger Pro click here.