## 20120924

### Online reading assignment: applications of Newton's laws, uniform circular motion

Physics 205A, fall semester 2012
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments.  Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect.  Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing a presentation on applications of Newton's laws, and uniform circular motion.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"Previously I never thought of force as a push or pull force, us humans apply some kind of 'force" in order to move and lift up stuff, and put down other stuff and never thought of how we are doing a mathematical movement all of the time.  I think it is very interesting how it was described that the direction of the force is very important and the magnitude not so much, since it is not a complete description.  Also by taking in consideration all of the forces that act on an object we are describing the net force.  Vectors are very important since by adding all of them gives us the net force mentioned above."

"How complex these normal everyday situations can be broken down into extensive analysis and calculations.  I think its interesting but is also way over my head."

"Normal forces--the fact that a table is pushing back on an object to ensure that the object does not fall through the table is fascinating."

"What looks like a smooth surface of a solid to the unaided eye is actually quite rough on a microscopic scale.  Friction is caused by atomic or molecular bonds between the high points on the surfaces of the two objects.  I find it interesting that even though something might look a certain way it really is much different if you look at it more closely."

"Two objects that are in constant contact with one another but have the same velocity exert static friction forces on one another because there is no relative motion between them."

"While an object appears to rotate at a certain speed, the outside of the object is actually moving faster than the inside."

"A uniform circular motion object must always have a nonzero acceleration because the direction of velocity is continually changing.  I was originally under the impression that if an object was moving in a circle at a constant speed, it could potentially have an acceleration of zero."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Newton's third law, trying to wrap my mind around it."

"The normal force between two objects--is the table exerting a normal force on the book and the book is exerting normal force on table or is there only one normal force between them?"

"Pulleys. What force is going where?  Why do they split?  When will that break?"

"I found some of the trigonometry confusing cause I hate trigonometry."
Ask the instructor an anonymous question, or make a comment.  Selected questions/comments may be discussed in class.
"It is really hard to read the material and understand it before we discuss any of it in class.  I feel like I only truly pick up what we learn in lecture!" (Hopefully by reading and struggling with the material before coming to class, you're 'primed' to ask questions and be more engaged with the material when it is presented in class.)

"Do you penalize wrong answers on the online reading assignments?  After I'm done with the reading but still not sure if I get the concept as I should" (Graded for completion, as long as there is a demonstrated effort towards reading and comprehending the material.)

"What happens if you push something with the same amount of force as the kinetic friction force?" (Sounds like a Newton's first law situation, assuming that you are pushing in the same direction as motion.)

"Will you please give us more examples during class?  Everyone would benefit by taking problems from the homework, as well as the next assigned homework and working through the entire problem step-by-step."  (I always attempt to show as much problem-solving in lecture as time allows, and will allot more problem-solving time in class before quizzes and exam.  Also the student solutions manual for the textbook, with many worked-out answers, is on reserve in the library.)

"When is our first exam? Not having one for this long leads me to believe that there will be a lot of material on it and I'm a little nervous."(The first midterm is October 10, and will cover Chapters 1-5.)