>
>Somebody with a better background in physics than I might like to
>calculate how much it takes to lift 150t of train 12cm above the rail.
It could be done with none at all.... just to keep it suspended there,
that is. No work is being done, you see, if no force is applied to
something in motion (vertically). You could do it with sufficiently
powerful permanent magnets. They sell executive toys that do this
this in novelty stores, the magnets hover in the air forever. Such
"toys" used to be part of the standard lab trivia supplied to high
school science labs- in my days.
Of course, energy is required to generate a non-permanent magnetic
field, but that's not terribly related to the weight that has to be
held up. As pointed out by David later, energy has to come from
somewhere, not necessarily the mag fields, to propel the device
against friction, up hills and to accelarate, etc.
Geoff Lambert