[opendtv] Re: Mag-lev
- From: "Kon Wilms" <kon@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 1 Nov 2006 01:59:20 -0500
> > > I recall a school physics puzzle in which we were asked to prove
> > > that if you drilled a straight line through the earth between
> > > any two points, you could operate a frictionless train using
> > > only gravity. The tunnels wouldn't actually be U-shaped, but
> > > straight lines bypassing the spherical surface geometry. Cute
> > > thought.
The trick part of this question is that is is impossible, since you have
to use power to maintain a stop at the destination in order for your
passengers to depart, lest the train be sucked back with the perpetual
sinusoidal gravitational pull. :)
The other parts of the trick question for minor points are that this
also assumes there is no other gravitational pull exerted on the earth
by other bodies, and that the density and mass of the earth is equal at
all points (in addition to being circular to a degree of infinite
accuracy).
I have always wondered about the other trick parts to this question..
are there any? I guess we could throw black holes and parallel universes
into the equation and say that the train is at all points simultaneously
and passengers are always embarking, travelling and departing at any
point in time, but that's another story eh? :)
Oh well just my 2c
Cheers
Kon
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