Blythy

some photos of the topping off added to here http://www.kdfansite.com/gallery/thumbnails.php?album=97 Bruce willis gets everywhere these days. http://www.kdfansite.com/gallery/displayimage.php?album=97&pos=43

conservation of momentum is related to a closed system. I.e. there's no energy that travels into or out of the group of objects under consideration. In TTD case, the system (in this case, the train) has a net transfer of energy into the system (i.e. the cable transfers energy to the train). The momentum of the train increases, as well as the momentum of the launch system. As there is a gain in both systems momentum, there is a net overall gain, and therefore no conservation. If you really want to apply conservation of momentum to a rollercoaster, consider a stalled train being stuck by a moving train. Then if you really want to impress, talk about the implications of this. (i.e. high accelerations, high jerk (how acceleration changes over time), bad for the train, bad for the people (will probably kill several people if it's above 30/40 mph) etc)

http://twitpic.com/qkyxo piece one going up.