Although I hate traveling during the school year, I thoroughly enjoy being around good physics teachers. Yesterday's AP Physics 1 Consultant Training in Chicago provoked interesting discussion, powerful insight, plenty of arguments, and other features of effective collaboration between teachers.
I'll distill the what insight I have about the new exams eventually. The AP Physics 1 and 2 curriculum framework is 150 pages worth of dense eduspeak. It's going to take a while to parse the text and expose the intent of the authors, especially when the College Board has released so few exam items. All I can say for now: The exams are beyond excellent, and you should teach to them.
The new exams will require significant amounts of quality writing. Gone are the days when "justify your answer" meant give one sentence with an equation. Students will have 90 minutes to answer about five free response questions; so the readers will expect adroit use of verbiage in those responses.
The Committee has spent years parsing their own language, so that every statement in the curriculum framework is self-consistent, and consistent with the language on the exam, and consistent with their perception of best physics teaching practice. Precision of language is, I agree, important in teaching first-year physics; I've written much on the subject. That said, sometimes pedantic consistency conflicts with common sense... while I'm more than willing to take a stand with students on the difference between "work is done by the gas" and "work increases", I'm not willing to call out someone who says "a 1 kg mass is thrown off of a cliff.* "
*Objects and systems have a property called "mass." Thus, it is imprecise to refer to a "mass." No, we should say "an object with a mass of 1 kg is thrown off of a cliff." While that's entirely correct, and I am glad the exams will be stated precisely, I have no intention of having an argument about such a subtle difference with a first-year student.
Even in the midst of what sounds like heinous baloney, useful nuggets emerge. On the tail end of the discussion about objects with mass, Jeff Funkhouser pointed out to me that he doesn't use the term "potential energy." Part of his reasoning I'd categorize as correct but pedantic -- since potential energy only can arise as a result of a conservative force, and since a force requires an interaction between multiple objects, it's not entirely correct to say that an object "has" potential energy. Rather, a ball at the top of a cliff has energy stored via the interaction between the ball and the earth (or between the ball and the earth's gravitational field); a mass* attached to a spring has energy stored via its interaction with the stretched spring.
The pedagogical point Jeff is making -- the point which I think is entirely correct -- is that this omnibus term "potential energy" gets in the way of understanding. Focus on the source or storage of the energy, not on the catch-all term "potential."
I'm in the midst of a 9th grade conceptual physics unit on energy. In any problem, we begin by writing in words the energy conversion: for example, "work done by a rope is converted to kinetic energy." That allows us to write the equation "Fd = (1/2)mv2." Finally, we can use semiquantitative reasoning to determine whether doubling the force of the rope doubles, more than doubles, or less than doubles the object's speed.
So consider a ball dropped from 2 m high onto a vertical spring. What's the energy conversion? I've trained my students to write "gravitational potential energy is converted to spring potential energy." But having read through stacks of papers, I see that Jeff is right. How often have I read "potential energy is converted to potential energy?" Or even with a correct statement of energy conversion, how many times have I seen the resulting equation written as "mgh = mgh"?
Enough already. The term "potential energy" is hereby banishéd from my classroom. We will instead write "gravitational energy is converted to spring energy."