what does a future doctor not need to know?

My big challenge in preparing my General Physics I syllabus is to figure out what to cut, when the majority of the students are pre-health. I cut thermodynamics, because we have learned that it is taught also in chemistry (and other places). I then wanted to add more material about fluids and elastic solids (pretty relevant to medicine, it seems), so what to cut? I ended up cutting most of rotation, spinning, and angular momentum. Why? To understand the body, you do need to know about torques (how does your arm work, static structures, and so on) but you don't really need to conserve angular momentum. Or do you? The centrifuge spins, but it doesn't have angular dynamics.

(I will be doing the centrifuge.)

rotation of solid objects

I spoke yesterday in class about rotating solid bodies, in particular when the object is spinning around an axis not aligned with one of the principal axes of the moment of inertia tensor. The challenging point is that if you fix the axis of rotation then you get bearing forces or torques, but if you spin torque-free then the axis of rotation necessarily precesses. Of course the details are pretty hard for a student seeing this material for the first time; many of my colleagues would drop this from an intro course. But I love mechanical engineering, and this particular process comes up just about everywhere in our every-day experience. I can't help but talk about it!

rolling down planes

Sanjoy Mahajan (MIT) and I have spent a lot of time talking about balls rolling down planes, in part because it is a very rich physics problem, and in part because it was the experiment that allowed Galileo to infer the constant acceleration behavior and galilean relativity. I started on this problem in class yesterday, but considering only the three energies: potential, linear kinetic, and rotational kinetic. When I asked the class to predict the outcome, I was surprised that I could get all three answers to the question "will the tube roll down the plane faster, slower, or at the same speed as a block sliding with little friction?" Even when we were done, not everyone got the inference, but I have to admit, the issue is subtle. Next time I will start to look at the problem from the point of view of forces; unfortunately, the class isn't quite ready for torques yet.