I have the good fortune to be a TA this year. I have never taught before, and this has turned out to be as much a learning experience (probably more so) for me as for the students. I think I have a nobel prize winner on my hands, though... In his/her discussion of the ballistic pendulum experiment, one student informed me s/he measured negative kinetic energy. I had to laugh... I know I know.. it's rotten to laugh.... but WOW. It rather frightens me that some of these students are going to go on to be engineers... no wonder rockets crash into the ocean... most of them can't convert units properly. Venting over.