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From: "Greg Neill" <gneill...@OVE.netcom.ca>
Newsgroups: rec.puzzles
References: <14601-3ECE603F-155@storefull-2316.public.lawson.webtv.net> <j_tza.208$6k3.202275934@news.nnrp.ca>
Subject: Re: Fast moving bird
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Message-ID: <ORKAa.55037$Em1.359663@wagner.videotron.net>
Date: Tue, 27 May 2003 10:45:29 -0400
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"Mark Brader" <m...@vex.net> wrote in message
news:j_tza.208$6k3.202275934@news.nnrp.ca...

>
> If you're riding on a train going north, parts of the train are going
> south.  Explain.

Train wheels have lips on their circumference that
extend a small amount past the track/wheel interface
on the outside edge.  Since the point of contact
of the wheel and track is stationary in the track's
frame of reference, the part of the wheel's lip that
extends below the track/wheel interface must be
moving in the opposite direction to that of the
train.