UPDATE: Questions about why we were doing what we were doing? Please see the FAQ under "MRI magnet quench: the movie." That video is also entertaining, btw.
Fun, games and safety implications with a 4 tesla (T) MRI magnet that was about to be decommissioned. Note how magnetic objects let loose tend to oscillate along the magnet bore. That's because the peak magnetic field gradients are at either end (near the magnet face), causing peak acceleration as the object enters, followed by progressively damped changes of direction. See practiCalfMRI.blogspot.com for more information.