"Spherical Cow" The title will make sense shortly... I gave 'reading quizzes' (algebra based Physics I and II) that are due before each lecture- these are 3 short-answer questions designed to identify student misconceptions prior to the lecture so that I can directly address any conceptual difficulties as they arise. Recently, when asked "why does a wire get thinner as it is stretched?", nearly every student gave a highly complicated response in terms of forces and stresses (when all I was looking for was conservation of mass/volume). I was genuinely perplexed, and when I asked the class why they gave such a complicated response, one student replied "well, I didn't think that the simple answer could possibly be correct, since nothing in this class is simple", which got a lot of knowing giggles from the other students. So I trudged into Jearl's office and we started talking about the 'intellectual baggage' students bring into class, and he mentioned that many students see the teacher as a magician who regularly turns one object into another- for example, turning a cow into a sphere. When he said that, I realized he was absolutely right- the next day I started the class by asking if I acted like a magician and got a lot of nods. I spent a recitation period trying to explain why I do that (abstraction of essential concepts, etc), but didn't get much of a response. The students have a lot of trouble relating real things to the idealized/abstracted models I create. Even when I have them step through the process: for example relating the free-body diagram of a car going around a turn to what happens when they are driving around a turn and hit a patch of ice, they can't make that leap. There's a persistent disconnect between what they know happens from experience and what they think happens "in physics world". I was just wondering if any of you all are aware of this (teacher as magician), if you have consciously tried to address this, or any other relevant ideas.