General College Physics

Wisconsin Lutheran High School

Week 14 (Nov. 10, 12, 13, 14)

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

Topics: torque, rotational inertia, rotational dynamics.

Quiz on Monday.

Week 14 exercises:

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?
Automobile problem: A 1500 kg automobile has a wheel base (distance between wheels) of 3 meters. The center of mass of the automobile is on at the center line at a point 1.2 meters behind the front axle. Find the force exerted by the ground on each wheel.
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). (a) How much torque does the 10 kg mass exert on the disk? (b) What is the angular acceleration of the pulley as the 10 kg mass falls? Is it constant? (c) What is the angular velocity of the pulley? Is it constant, or time dependent? (d) The floor is 3 meters beneath the release point of the 10 kg mass. How long does it take to hit the floor? (e) What is the speed of the mass just before it hits the floor?
Rotational inertia laboratory: This week, we will be working with a rotational inertia apparatus. The goal is to predict how much time it will take for a falling mass to strike the ground. The falling mass, however, is suspended from a string which is wrapped around a rotatable shaft.

First, carefully measure the masses on the crossbeam and their locations. From this, determine the rotational inertia of the apparatus. Be sure to include an estimate of the rotational inertia of the vertical shaft.
Now measure the mass that is to be dropped. Also, measure the distance between the mass and the floor.
Set up a free body diagram and attempt to predict the acceleration of the falling mass. Don't forget that the tension in the string is supporting it!
From the acceleration and the distance, predict the time of fall. Put a box around your prediction. Now get your instructor to come watch your falling object. Determine the percent difference between your prediction and your experimental results.
How might your experiment be done better?

General College Physics

Return to course website.

Course syllabus

General College Physics is a year-long introductory college-level course for advanced (typically junior or senior level) students at Wisconsin Lutheran High School. It is a dual-credit course offered at Wisconsin Lutheran High School in collaboration with Wisconsin Lutheran College. This means that students enrolled in the course have the option of receiving credit for a four-credit algebra-based laboratory science course from the College.

During the first semester, we will primarily study the science of motion and its relationship to forces. Topics include: dimensional analysis, measurement, uncertainty, estimation, two dimensional kinematics, projectile motion, newton’s laws, force diagrams, centripetal force, circular motion, conservation of energy and momentum, torque, angular momentum, oscillations, and gravity. During the second semester, we will explore a number of inter-related topics including: heat, thermometry, the laws of thermodynamics, electricity, magnetism, optics, electromagnetic induction, radiation, atomic theory, and nuclear physics.

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!

Course textbook: The course will be loosely 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 on a rotating schedule in WLHS 223—the science wing on the first floor of WLHS.

Professor: Dr. Kuehn from Wisconsin Lutheran College (WLC) is the professor for this course. Best contact info: kerry.kuehn[at]wlc.edu

Registration for College Credit: Wisconsin Lutheran College is requiring students in this course who are interested in obtaining college credit. Please apply in the application link below for each class you are wishing to apply for college credit. This must be approved by Friday, September 27.

https://admissions.wlc.edu/register/foundations

Once students apply we will wait for Wisconsin Lutheran College to confirm eligibility and requirements for college credit and communicate out further information. Please reach out to Mr. Davis if you have any questions.

Teaching Assistants One day each week (beginning in September) the course will be overseen by teaching assistants Richard “Ricky” Hill and Henry Brown. Both are physics major enrolled at Wisconsin Lutheran College.

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/WLHS/

Homework exercises: II will assign weekly homework problems. These are designed to deepen your understanding of lecture material and to prepare you for the quizzes and tests. Although I do not intend to regularly grade your homework solutions, I will occasionally do “spot checks” to make sure that you are keeping up with the material. I plan to give credit for submitting your best attempt by the assigned due date (typically Sunday late afternoon). Late assignments will receive reduced credit.

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 scanned and submitted electronically as a single file 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 final exam before the end of the second quarter, and a comprehensive final examination before the end of the fourth quarter.

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.