20150909

Online reading assignment: projectile motion, forces/interactions

Physics 205A, fall semester 2015
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 projectile motion and forces/interactions.


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.
"The concept of a projectile's motion being a combination of a constant horizontal motion and the force of gravity acting on it vertically."

"How to determine vertical and horizontal velocities derived from an initial velocity. Also, the different kind of forces acting on an object and how to illustrate their magnitude and direction in a free-body diagram."

"I understand the formulas but I know need to work on using the formulas."

"A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects."

"There are at least five types of force; weight, normal, tension, static friction, and kinetic friction. Weight is a product of mass and gravitational strength, normal force is exerted by and is perpendicular to a surface, tension is exerted along a line of some sort."

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 am still having trouble picking out the correct equations to use!"

"All the abbreviations for all the terms... Can you define all the v0x and v0y and all that junk so I know what I'm looking at? Thanks."

"I did not find anything particularly confusing."

"Finding the angles is still really confusing for me. I have a hard time figuring out what θ is and I need more practice with that."

Describe a situation with a negative (starting) angle of elevation for projectile motion.
"A jet firing a missile at an object on the ground."

"An archer standing at ground level shooting at an object below him."

"A car driving down a hill and then off a cliff."

"If an object is launched straight down."

"Someone fishing with a gun."

"I'm not clear on what this question is asking for."

Identify the type of interaction ("force") with its symbol. (Only correct responses shown.)
Weight ("gravitational force") : w [94%]
Surface contact force ("normal force"): N (or FN) [92%]
Tension ("rope/cable/string force"): T [96%]
Kinetic friction ("sliding force," or "sliption"): fk [94%]
Static friction ("sticking force," or "stiction"): fs [92%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can you see the time when we submit these assignments? Do you judge us for doing this at the last-minute? {shy monkey emoji face}" (Yes, your responses are all time-stamped. {frowning judgey emoji face})

"Are the midterm problems going to be similar to our homework problems?" (Most of the midterm is comprised of conceptual questions that require explanations. So they're like some of the in-class worksheet questions, in that you apply your analytical skills and show your reasoning.)

"Still don't feel super-solid about projectile motion so help, please, would be awesome. A few more examples would really help." (We'll start putting together all the pieces that we've been dealing with separately (initial velocity vector components, constant horizontal motion, free fall vertical motion) in the upcoming in-class examples.)

"Do you know of anyone with a room for rent? I've been homeless for the past eight days now. lol." (I'll be sure to pass on any responses from your classmates if they have a lead.)

"We have a lot of people in this class." (At UC-Davis my physics class was divided up into two separate lecture sections of up to 200 students each. And also 20-25 separate lab sections.)

"What did you do for Labor Day weekend?" (Mrs. P-dog and I did this. What did you do?)

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