Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/5/84; site reed.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!houxm!vax135!cornell!uw-beaver!tektronix!reed!alexis
From: alexis@reed.UUCP (Alexis Dimitriadis)
Newsgroups: net.jokes,net.puzzle
Subject: Re: Manhole covers (interview question)
Message-ID: <1196@reed.UUCP>
Date: Fri, 29-Mar-85 01:57:03 EST
Article-I.D.: reed.1196
Posted: Fri Mar 29 01:57:03 1985
Date-Received: Sun, 31-Mar-85 02:49:39 EST
References: <462@nbs-amrf.UUCP> <7074@watdaisy.UUCP> <474@nbs-amrf.UUCP> <237@vaxwaller.UUCP>
Reply-To: alexis@reed.UUCP (Alexis Dimitriadis)
Organization: Reed College, Portland, Oregon
Lines: 46
Xref: watmath net.jokes:11593 net.puzzle:660
Summary: 

>> 
>> > > > 	Why are manhole covers round?
>> 
>> Also, why doesn't a manhole cover (of any shape, but let's stick to round
>> ones) fall into the manhole? It is because there is either a ledge on which
>> it rests or the opening is beveled.  In either case, I claim that all
>> regular polygons of sufficiently high order approximate a circle closely
>> enough that they will not fall into the hole, either.  
>> 
>Certainly no four sided cover will work
>and it seems likely that you would have to approximate a circle so closely 
>as to be pointless.  Was the original question theoretical or practical ?
>
>Bob Palin,  zehntel!varian!bob

(Naturally, net.jokes is an inappropriate place for this discussion, but
I find it interesting).

  Think about what "beveled" means.
Yes, even a square cover will not fall in its hole if bevelled enough.
(Think of it as essentially upside-down pyramid shaped).
Clearly, anything larger number of edges would work better and better.

  Someone pointed out that you can roll a round cover into place.
A round cover can also be dropped in its hole without concern for
alignment, unlike any polygonal shape.  Besides, has anyone realized
that round manhole covers generally cover round manholes?  A round
manhole (cylinder) has the smallest surface-to volume ratio possible,
and is therefore cheaper.  (Sewer pipes are also round.  Anyone care to
speculate on why?).

  Let me add a plea to restrict future discussion to net.puzzle, and
net.manhole.cover.  The plea doubles as the obligatory joke, since noone
will follow it. 
			Facetiously,
			alexis

PS.  The discussion on the Roullaux (sp?) drill was rather interesting.
Does anyone know the actual shape of the drill? 

-- 
_______________________________________________
	  alexis @ reed
	...ihnp4!{harvard|tektronix}!reed
	...decvax!tektronix!reed
	...teneron!reed