20130916

Online reading assignment: forces and motion

Physics 205A, fall semester 2013
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 forces and 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.
"There is a difference between mass and weight. I believed that they were the same thing but after reading the books example of a shuffleboard puck it makes perfect sense as to why they are different."

"When speed and direction are constant the sum of the forces is zero."

"I did not know that forces could 'cancel' each other out."

"Net force."

"The motion flowchart, because it points out exactly which newton law is needed."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I am incredibly confused about inertia! I need visuals and examples. The book throws out a bunch of definitions and I became increasingly confused."

"I'm still not 100% when Newton's first law is applied and when his second law is applied. I understand that Newton's first law needs constant speed but I still don't quite grasp the idea of it all."

"The motion flowchart and the subsequent slides of the presentation were confusing because Newton's first and second laws were not defined before going through all of the slides."

I wasn't sure which category of Newton's law the landing F-35B was in."

"I think that this section was straightforward for me."

"I am confused with the concept of net force. I understand when and what equation to use depending on the net force but I don't understand when forces acting on an object will create a zero net force. Must they always be opposite and equal magnitude?"

"Vector forces."

"Deciding if the net force is zero or not."

There could be as few as __________ (non-zero) force(s) acting on an object, such that the net force would be zero.
one.  ************** [14]
two.  ************************* [25]
three (or more).  ***** [5]
(Unsure/guessing/lost/help!)  ************ [12]

For all cases of a moving object with zero net force exerted on it, its speed must be:
decreasing.  ** [2]
constant.  ********************************************* [45]
increasing.  [0]
(More than one of the above choices.)  ***** [5]
(Unsure/guessing/lost/help!)  **** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can we please go over the shoveling snow example from the book and relating it to inertia?" (The non-sticky dry snow coming off of a shovel is like Mini-Me in this clip. No forces exerted, then no change in motion.)

"Why is the acceleration of an object proportional to the net force acting on it?" (This is always observed to happen. So let's turn it around, from instead of asking why this is always observed, to saying that it mustbe a law that is always obeyed!)

"What if only one force acts on an object? I'm unsure if it it could be Newton's first law, because how does it cancel out?" (If only one force acts on an object with no other forces available to cancel it out, then the net force is non-zero, making this a Newton's second law case.)

"The whiteboard lecture notes posted on Twitter were really helpful to study for the quiz."

"Twitter? What is Twitter? How does Twitter work?" (As noted in the syllabus, search for the hashtag: #CuestaPhys205A for course-related announcements.)

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