Can anyone answer how far a magnet rail can make a ball travel?

[Shakti]

Hi, thanks for reading this. If the question has been answered before please forgive me asking it again.

Q: Does anyone know what is the longest distance a bearing is able to travel along a (non-electric) magnet rail device in a straight line? It can be level or up hill whatever, just trying to understand the distance possible. I have seen different devices on Youtube, but none seem to go very far. One person says it will travel indefinately, another says it will slow down. What do you think and are there any actual experiments to show that it is possible? Maybe 10 metres? 100m?

Here is a YouTube vid for reference as to what type of device the question refers to.

http://www.youtube.com/watch?v=8zGh64Eo8yk&feature=related

Thank you for your answers and any references.

Regards, Shakti

[Blainiac]

For it to go infinitely far, it would have to have an infinitely powerful magnet at one 'end' of the infinitely long track.  I'm not sure exactly how far it can practically travel, but I would think it would depend on the distance of the track and the difference in magnet strength throughout the track.  I'm sure there's a limit to how far you can go...

This being said because if the small difference between two magnets on the track (let's say in the case of the video) is too small (because you increased the track size largely), the bearing will not be pulled enough to the next one in the track.  That's what I would think anyway with regard to making a track longer...  unless you had bigger magnets at one end...