Re: [boost] Boost Units library preview

From: Eric Lemings (lemings_at_[hidden])
Date: 2006-08-23 12:30:45

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Andy Little
> Sent: Wednesday, August 23, 2006 10:15 AM
> To: boost_at_[hidden]
> Subject: Re: [boost] Boost Units library preview
> 
> 
> "Phil Richards" <news_at_[hidden]> wrote in 
> message 
> news:20060823145751.6C0A0AABB8_at_derisoft.derived-software.demon
> .co.uk...
> > On 2006-08-23, Matthias Troyer <troyer_at_[hidden]> wrote:
> >>  - Nm would be a "dimension"
> >
> > Not really.  It is the unit.
> > The dimension is: MASS * LENGTH^2 * TIME^2
> >
> >>  - 1 Nm would be a "quantity"
> >>  - a torque measured in Nm or an energy measured in Nm 
> would be two  
> >> distinct units
> >>  - 1 Nm as torque, 1 Nm as energy or 1 J as energy would be three  
> >> distinct measures
> >
> > I think as far as a dimensionality checking goes, they are all the 
> > same.  As far as a units checking goes, Nm and J
> > *could* be distinguished.  It's an interesting question as to what, 
> > exactly, "energy" and "torque" are once you try to separate 
> away the 
> > dimensionality and units bits... :-)
> 
> FWIW If I use a hefty spanner to undo a rusty bolt, then the 
> bolt heats up as I unscrew it. I guess the heat energy gained 
> by the bolt is directly equivalent to the torque I had to 
> apply to undo it.  OTOH  therefore one would think that 
> applying heat to a rusty bolt should make it unscrew itself 
> but unfortunately for some reason I have never been able to 
> get that to work !  ;-)

Because what does heat do to the bolt?  It makes it expand and thus
harder to turn.  So I guess if you froze it, it would be easier to
unscrew?

Disclaimer: "I am not a physicist.  I just act like one sometimes."

Eric.