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From: peterv@runx.OZ (Peter Vels)
Newsgroups: net.math
Subject: Fly and train
Message-ID: <508@runx.OZ>
Date: Sat, 12-Oct-85 01:05:45 EDT
Article-I.D.: runx.508
Posted: Sat Oct 12 01:05:45 1985
Date-Received: Tue, 15-Oct-85 04:44:42 EDT
Organization: RUNX Un*x Timeshare.  Sydney, Australia.
Lines: 19


In previous articles I have noted that flies "turn around in zero time".
Following on from that idea, can anyone explain the following story in
mathematical terms to me?

A fly is heading south above some train tracks.

Unluckily for him, a train is heading in the opposite direction.
They collide.
Assume that before the moment of impact the fly and the train were
moving at the same speed (ie. the train's velocity = -(fly's velocity).
After impact, the fly (now dead) is stuck to the front of the train.
In order to "turn around" (change from a positive velocity to a negative one)
the fly must have had a zero velocity at some point in time (my assumption).
Having a velocity of zero, the fly must have been stopped.
At that time, the fly would have been in contact with the front of the train.
As the two bodies were not rotating, would not the train have been stopped as 
well?  If not, then why not?

Peter Vels.