For our end of the year project we chose to do magnetic levitation (not the smartest choice in retrospect). There are usually two ways to do this. One is to run an electric current and create a magnetic field so the platform and the track repel, and another is to just use bar magnets (as the track and attached to the platform) which will repel each other if the poles are simply set correctly. We chose to do the latter, as it spares us from doing any RHR or actual physics like that. We tried (I believe) 3 designs, each using 3 of the same size pieces of wood as walls and a floor for the track. Our first attempt at the track was to take eight bar magnets and lay them horizontally across our approximately 3 inch wide track (magnet's length is 2 inch, width is one, so we laid them lengthwise like | | | | etc. Since they attract each other like that though, to hold them in place we used flathead screws to pin them down. We also put little disc magnets (not as strong, two of each) between each set of bar magnets for better repulsion. This idea did not work, however, as the only flathead screws we could find had metal in it, and thus would become magnetized and actually attract our platform (which, until the end, was just cardboard with a single bar magnet on top). So the platform would be repelled by the magnets but attracted by the screws, and did not work at all.

So we took out the screws and just taped everything down. This also did not work, since the magnet on our platform was attracted by the edges of the magnets (essentially the same problem as with the screws).

We then took the tape and all the magnets off, then turned the magnets so they followed the track like - - - - - -. This reduced the problem of attraction, and adding the little disc magnets in between the bar magnets reduced it further (track looked like -o-o-o-o-o- except the o's are smaller...). Unfortunately, Nick and I could not, at the time, figure out a way to reduce tipping/attraction to the track. Luckily, this is where Tim came in (and Nick too, I know he wants credit, and I don't really deserve any since I was writing the letter at the time). Instead of just one magnet on the platform, he took two and arranged them on either end of a rectangular platform (with a cutout in the middle to reduce weight). This solved not only the tipping (simply by sheer counterweight), but also the attraction of the platform to the track (for, if you can picture it, when one magnet is attracted to the track, the position of the other one is such that it will balance the force). He also added tape on the walls to help it glide easier, and with that the project was finished. Cleanest, neatest project? No. Effective (in the end)? I would say so.

I realize that this is hard to visualize, but I don't have a picture so this is the best I could do. Anyway a great way to end a year of Physics C!