What is Mathematical Modeling?
You might think this to be a simple, straightforward answer, but unfortunately we have no such luck. The definition of mathematical modeling varies depending on the author unlike other more clearly defined mathematical terms like prime or group.
Arguably, one leading mathematician in the field of modeling is Pollak, former Bell Labs director who has also been an educator for the past 30 years or so. In his chapter A History of the Teaching of Modeling in Stanic and Kilpatrick's A History of School Mathematics, he opens with providing a clean definition for mathematical modeling. To quote from here:
What distinguishes modeling from other forms of applications of mathematics are (1) explicit attention at the beginning to the process of getting from the problem outside of mathematics to its mathematical formulation and (2) an explicit reconciliation between the mathematics and the real-world situation at the end. Throughout the modeling process, consideration is given to both the external world and the mathematics, and the results have to be both mathematically correct and reasonable in the real-world context. (p. 649)
Pollak goes on to describe an 8-step process that form mathematical modeling. These 8 steps can be split apart into different groupings to form other types of mathematics [e.g., "'Applied mathematics'" is traditionally a name for a collection of fields of mathematics that arise frequently in step 5." (p. 650)].
An abridged version of these 8 steps are below. [For the full version see H. Pollak, Solving problems in the real world, in Why Numbers Count: Quantitative Literacy for Tomorrow's America, (ed.) L. Steen, College Board, New York, 1997, pp. 91-105.]:
- Identify the real-world problem;
- Identify important factors on which to focus;
- Select which factors and which interrelations to keep and which to toss away;
- Translate the real-world problem into a mathematical one;
- Identify the mathematics required;
- Use mathematics to determine results;
- Translate results back into the real world; and
- Determine if your answer is reasonable. If it is, report on this. If not, repeat the process.
Common Core Definition
More recently, the authors of the Common Core have brought mathematical modeling to the forefront by placing it prominently within their standards document. It appears in two distinct locations: First, as one of the 8 Standards for Mathematical Practice and then again as a High School Standard unto itself. What is unique about this second appearance is that it does not provide bite-sized content pieces (e.g., CCSSM.HSG.C.A.4) as do all of the other sections (e.g., Geometry or Grade 4). The authors do define mathematical modeling in the High School section as:
"the process of choosing and using appropriate mathematics and
statistics to analyze empirical situations, to understand them better,
and to improve decisions."
Note that while there are similarities here to Pollak's definition above, the emphasis on the movement from the real world to the mathematical one, and back again, does not appear.
The Common Core authors do choose to include what I call "visual maps" of mathematical modeling. (Note, it was originally included in the PDF versions of the Standards but has become difficult to find on the online version.)
This image does call to Pollak's definition of re-cycling through the steps if needed.
Are any of your Calculus questions modeling?
Based on Pollak's definition, I would say as stand alone problems, that no these are not modeling problems. Being given specific problems like these takes away from the earlier steps in the modeling process that Pollak indicates. It is certainly possible to use these problems as parts of the modeling process, and even to adjust them to include many or all of Pollak's requirements.
Based on the Common Core definition, I might claim that yes all of these could be considered modeling problems, as long as these are based on empirical and not theoretical situations (which could be argued in and of itself).
As for my personal opinion, I think that the Common Core definition is (understandably) lacking in some of the areas that Pollak's definition seems to detail. On the other hand, Pollak's definition might make it difficult to ever deem any textbook or teacher provided problem as modeling. The definition of mathematical modeling is very much in the eye of the beholder.