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.
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.
"I found the nutcracker interesting because I'm still not quite sure how it works."
"Never really had any idea what torque was before this."
"That the mechanic could not have loosened the nut doing what he was doing."
"I find it interesting that every topic relates back to Newton's laws."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Lever arms--I get confused because I keep drawing my lines in the wrong directions."
"Rotational equilibrium--I did not fully understand the logic behind the idea that the net force acting on an object could be zero, while the net torque is nonzero."
"Line of action--I figured it would be easier to just break your applied force down into vectors, and use only the one that is perpendicular to the lever arm."
What is the SI unit for torque?
"N·m, or J."
"N·m, but should not be referred to as a joule because torque is not a form of energy."
Briefly explain when a (+) or a (-) sign should be assigned to a torque value.
"A positive sign indicates a rotation in the counterclockwise direction, while a negative sign is a rotation the the clockwise direction."
"It is determined by the sign of angular acceleration if the torque was working alone. When determining the sign, we think about the direction in which torque would make an object spin if it is initially motionless."
Briefly describe how a line of action should be drawn for a given force.
"Along the force vector."
"Please explain."
When a lever arm (or moment arm) is drawn, briefly explain where it starts, and where it ends.
"The lever arm starts from the rotation axis and ends at the line of action."
"It starts at one end at the pivot point, and intersects the line of action at a perpendicular angle."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"If a joule is also expressed as N·m, what is the difference between energy and torque, mathematically? How can they have the same units but not be the same?" (Work is the "dot product" of force and displacement, while torque is the "cross product" of force and lever arm. For the purposes of this course, dot products and cross products will behave similarly to multiplication, but they're actually two distinct mathematical operations.)
"How much extra credit is available?" (As much as you need. But not any more than that. Trust me on this.)
"Would you post the answers to our flashcard questions somewhere? We need more problems/examples to go over in class. This flipped class method is not very effective, so far when the midterm average was a 'D.'" (E-mail me your answers to flashcard questions not discussed in class, so I can "grade" them and give you feedback on what you missed. Yes, I will be working on more examples this week. The midterm average was actually a "C," and the class average for the course so far is a "B"--refer to the course syllabus for the grading scale.)
"Will we also be looking at rotations that are not in equilibrium?" (Yes, but from an energy conservation approach.)
"So I bombed the midterm, like not a good bomb when people walk up to each other and say 'you're the bomb,' I bombed it like every time I try talking to a girl and I totally blank and she walks away. Can I survive the rest of this semester?" (From our discussion last class, to extrapolate your grade to the end of the semester: double your total points so far, then add a reasonable amount of points achievable on the Final Exam (out of 100 points). If this is more than 500 points (as for your case), you're at a "B" pace so far.)
"I wasn't huge on the flipped classroom at first, but I've definitely grown to like it a lot more!" (You and me, both.)
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