In reply to Terry Blanton's message of Tue, 8 Jan 2008 07:39:31 -0500: Hi, [snip] >I don't follow you. The presence of the magnets changes the momentum >of the ball regardless of the initial PE as long as it does not >change. [snip] That's just the problem. The initial PE does change, because it doesn't only comprise the gravitational PE due to the height of the track, but also the magnetic PE between the magnets and the ball itself. IOW the ball can "feel" the magnets even at the starting position. That may mean that you have to do a little more work with your hand to place the ball on the track when the magnets are present than when they are not, or you may need to push the all a fraction harder to get it to start rolling down the track. The latter can easily be eliminated by making the track slope down at the start, and using a barrier to hold the ball in place. Removing the barrier would not add energy to the ball. However that still doesn't solve the first problem. The only way I can see around that is to make the whole track a closed loop. The problem is thus that the work you do with your hand doesn't get measured.
BTW still on the topic of magnet motors, the video that was posted recently matches the description I saw in a magazine (I think) years ago of a magnetic generator that was supposed to have been used by the US Army in Vietnam. It also comprised two magnetic discs making contact at the rim, but the axes were not quite parallel, and the discs were about the same size. Regards, Robin van Spaandonk The shrub is a plant.
