20150916

Online reading assignment: Newton's third law

Physics 205A, fall semester 2015
Cuesta College, San Luis Obispo, CA

Students have a bi-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 Newton's third law.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"Every force is an interaction between two objects; such that all forces come in pairs."

"There are two different yet valid ways to describe each force--one from the point of view of object 1, and the other from the point of view of object 2."

"Newton's third law states that every force has an equal and opposite force, but the law only applies when the forces are opposite, of the same type, and involve exactly two objects. But even when Newton's third law applies and two forces are equal, those forces will not always have the same results on either of the two objects involved because different mass values will produce different accelerations even if the forces are equal."

"N1: an object stays at rest, or moves, at a constant velocity and direction unless impacted by a net force. N2: an object's speed and/or direction of velocity changes by a net force, and the direction of the acceleration is the same as the direction of the net force. N3: each forces is an interactions between two objects."

"That the weight of the object is the gravitational force that is exerted on an object while it is on or above Earth. I always assumed weight and mass were just the same thing."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"I understand the explanation of the things discussed in the reading, I just would like to see some examples of applying and computing all of the different concepts."

"Nothing in particular as of now, though I didn't yet get to implementing the new concepts and equations in practice."

"Nothing was too confusing. We just need to go over more problems in class as well as go through the more important concepts you want us to understand."

"I do not understand the questions below on distinguishing between N1 or N3 force pairs. Otherwise everything seemed straightforward."

"We should go over more problems in class on how to distinguish between all three Newton's laws, I think that will help me a lot."

"The difference between Newton's first law and Newton's third law."

Consider two categories of motion: (1) Velocity that is constant and unchanging. (2) Velocity that is changing. Discuss whether or not there would be a third category of motion not already covered under these two categories.
"Motion in a circle: where speed is constant but the direction of velocity is always changing?"

"A stationary object with no motion?"

"There is no third category of motion, because the two categories listed above encompass all types of motion. For there to be a third category there would need to be a type of motion that was either both constant and changing, or neither constant nor changing, which is impossible."

"There probably is, but my brain can't even \_(*~*)_/" (There are three types of students: (1) Those who understand binary. (2) Those who don't.)


According to Newton's first law, the normal force of the person's head on the stack of books is equal in magnitude and opposite in direction to the:
normal force of the stack of books on the person's head.   *************** [15]
weight force of Earth on the stack of books.   ***************************** [29]
(Both of the above choices.)   ************ [12]
(Neither of the above choices.)   ** [2]
(Unsure/guessing/lost/help!)   ** [2]


According to Newton's third law, the normal force of the person's head on the stack of books is equal in magnitude and opposite in direction to the:
normal force of the stack of books on the person's head.   ********************** [22]
weight force of Earth on the stack of books.   *********************** [23]
(Both of the above choices.)   ****** [6]
(Neither of the above choices.)   ** [2]
(Unsure/guessing/lost/help!)   ******* [7]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"For the OST ('of the same type') in the POF-OST-ITO checklist, does it have to be two forces exactly of the same type? w = -w, N = -N, T = -T, fs = fs, fk = fk? Is that possible in real life?" (Yes.)

"I would greatly benefit to more practice problems and examples that involve Newton's third law." (Yes.)

"What's your favorite color?" (Eh, I'm partial to 493 nm.)

"What is your quest, Dr. P-dog?" (Doing more of this with Mrs. P-dog.)

No comments:

Post a Comment