Re: [Phys-l] Q: Why are manhole covers round?

[Bernard Cleyet <bernardcleyet@redshift.com>]

Is this advertising for Hampton Sides book?

bc, who has too many books to find his copy quickly.

Cliff Parker wrote:

> Why is a moth attracted to light?  Is it because they love light and want to 
> bask in its glory or because they hate it and want to attack it?
>
> ----- Original Message ----- 
> From: "Bernard Cleyet" <bernardcleyet@redshift.com>
> To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
> Sent: Sunday, May 21, 2006 12:11 AM
> Subject: Re: [Phys-l] Q: Why are manhole covers round?
>
>
>  
>
> > I suppose that's why triangular ones are hinged.
> >
> > bc, first quizzed on this by the late Ron Ruby in 1984.
> >
> > p.s. any constant diameter figure will work e.g. Rouleaux triangle.
> >
> > John Clement wrote:
> >
> >    
> >
> > > It is probably because you do not want the covers to accidentally fall 
> > > into
> > > the hole.  A square one can be oriented so as to fall through, but a round
> > > one can not.
> > >
> > > This reminds me of the question "Why do gorillas have big nostrils?"  The
> > > answer is because they have big fingers.
> > >
> > > John M. Clement
> > > Houston, TX
> > >
> > >
> > >
> > >      
> > >
> > > > A:  Because the manholes are round.
> > > >
> > > >
> > > > (Something to keep in mind when discussing "cause and effect".)
> > > >
> > > >
> > > >        
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> > >
> > >
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