Re: ballistic subterranean trains

From: Spike Jones (
Date: Wed Sep 26 2001 - 20:20:15 MDT wrote:

> Spike writes:
> ...
> > If it is going sufficiently fast, the centripetal acceleration
> > equals the acceleration due to gravity at that point, so the
> > occupants of the car are temporarily wieghtless. If the
> > tunnel is any steeper, the occupants experience negative Gs.
> I don't believe this is correct. Centripetal acceleration only applies
> to circular motion, and the car is going in a straight line... Hal

Doh! Hal is right. I incorrectly remembered having done these
calcs a few months ago, and I had a straight tunnel tangent to
a circular tunnel at some depth. My calculation of depth would
work if the tunnel went down at 35 degrees, met up with a
circular tunnel at a constant depth in which the train car would
be weightless, orbitting inside the planet, then later tangent
to another straight tunnel going back up to the surface.
Thanks Hal! spike

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