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 elasticity.
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.
"Tension is when you stretch something and compresion is when you squish something."
"Hooke's law can show how the material will respond to stress being applied to it."
"Stress is the application of a force, while strain is the measure of how the material responds."
"Tension is the stretching of something while compression is the squishing of something."
"Stress is defined as the force per unit area of a material. Stress = force/cross-sectional area. Strain is defined as extension per unit length. Strain = extension/original length."
"I understand the concept of restorative force applied by a spring when you stretch or compress it. The spring is always going to 'want' to return to its original length."
"Most of it was confusing."
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'm not quite understanding how these variables such as tension, stress, and strain are all connected, is it just through Hooke's law or is there something else that will connect them?"
"Well I could use a run-through on Hooke's law and how we solve it. as well what each of the symbols represent in-depth."
"The whole section on Hooke's law confused me. I just really didnt understand what was being put into the equations, except for the moduli for differing materials."
"Everything in this reading actually made perfect sense to me, there really wasn't anything that I kind of found confusing. Maybe Hooke's law, but I read it over a couple times and it makes sense now."
"I didn't find much confusing since I feel like this chapter is pretty straightforward."
What is the SI (Système International) unit for stress?
"Pa."
"N/m2."
Explain why strain is a unitless quantity.
"strain is dimensionless and have no units."
"It's the ratio of two lengths."
"Because its a fractional change?"
"Strain is unitless because it is a fraction of the change in length over a length so the units cancel out. "
"I'm not sure."
"Not sure, I just know it is."
What is the SI (Système International) unit for Young's modulus?
"Pa."
"N/m2."
shorter. ****** [6] longer. ******************** [20] (There is a tie.) ***** [5] (Unsure/lost/guessing/help!) ******** [8]
narrower (two 2×4s). ****************** [18] wider (three 2×4s). ***** [5] (There is a tie.) ******* [7] (Unsure/lost/guessing/help!) ********* [9]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"For collisions, the definition of an elastic collision is that all energy is conserved, and there is no permanent damage. So why is that that there's permanent damage here if it's called elastic deformation?" (Actually, it's only called elastic deformation as long as when you let the material relax, it can still return (unharmed) to its original, undamaged state. If you do stretch or squish the material such that you irreversibly damage it, then you've exceeded its "elastic limit" (cf. p. 279 from the textbook).)
"How do we set up and work through these type of problems?"
"I would like to go over some practice problems in this section."
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