Online reading assignment: uniform circular motion

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 uniform circular motion.


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.

"A centrifugal force appears to push outwards on us when in fact the net force acts inwards, to keep it moving in a circular motion."

"The requirement for uniform circular motion is that the net force must be exactly equal to mv²/r, and be directed in towards the center."

"Uniform circular motion is related to Newton's second law."

"An object in uniform circular motion is constantly accelerating towards the center of the circle. A 'centripetal' force is not actually a force; it just describes the net force acting towards the center of a circle in uniform circular motion."

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.

"Everything. I have no idea how to apply any of these concepts and barely understand the basics of them."

"I have a preliminary understanding of circular motion, at face value, but I think it would be very helpful to go over examples in class."

"I think I understand this part pretty well."

For the "drifting" car (skidding around a circular track at constant speed), Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:

first; is zero.	******** [8]
second; points to the left.	*********************** [23]
second; points to the right.	*********************** [23]
(Unsure/lost/guessing/help!)	**** [4]

At the moment when the woman is at the bottom of her swinging trajectory (when the rope is vertical), Newton's __________ law applies to her motion, and the forces acting on her add up to a net force that:

first; is zero.	**************** [16]
second; points upwards.	*************************** [27]
second; points downwards.	********** [10]
(Unsure/lost/guessing/help!)	***** [5]

At the moment when the motor scooter is on the left side of the screen (traveling out at you), Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:

first; is zero.	********* [9]
second; points to the left.	***************** [17]
second; points to the right.	************************ [24]
(Unsure/lost/guessing/help!)	******** [8]

At the moment when the car is at the very top of the loop-the-loop, Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:

first; is zero.	***************************** [29]
second; points upwards.	********* [9]
second; points downwards.	************************* [25]
(Unsure/lost/guessing/help!)	**** [4]

At the moment when a person is at the right edge of the screen (traveling out at you), Newton's __________ law applies to his/her motion, and the forces acting on him/her add up to a net force that:

first; is zero.	*** [3]
second; points to the left.	************************** [26]
second; points to the right.	***************** [17]
(Unsure/lost/guessing/help!)	************ [12]

At the moment when the car is at the very top of its mid-air trajectory, Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:

first; is zero.	************* [13]
second; points upwards.	********** [10]
second; points downwards.	*************************** [27]
(Unsure/lost/guessing/help!)	******** [8]

At the moment when the skateboarder is at the very top of his mid-air trajectory, Newton's __________ law applies to his motion, and the forces acting on him add up to a net force that:

first; is zero.	***************** [17]
second; points upwards.	***** [5]
second; points downwards.	****************************** [30]
(Unsure/lost/guessing/help!)	****** [6]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I'm confused as to how circular motion applies to everyday life. I'm not fully understanding how the pictures show the centrifugal forces." (A "centrifugal" force is not one of the actual mechanical forces (w, N, T, f_s, or f_k). #smh)

"I'm not sure which way the net forces are acting in the examples above, so I was taking educated guesses." (#facepalm)

"Are the the net forces always towards the center of the circle (downward if at the top, upward if at the bottom, right if it's going left, left if it's going right)?" (Yes--yes, yes, yes, and yes.)

"Do we get marked down for checking 'unsure/lost/guessing/help!' or 'honestly didn't get to it yet' in our online homework?" (You will still receive full credit. Unless you leave the comment boxes blank, so put something substantive in there--even if you got nothing, at least tell me what's going on in your life that is interfering with studying physics this week.)

"7-Up or Sierra Mist?" (Meh. I do miss dnL, which was the "uʍop ǝpᴉsdn" edition of 7-Up.)