Re: [boost] Boost Units library preview

From: Andy Little (andy_at_[hidden])
Date: 2006-08-23 12:15:10

"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 !  ;-)

regards
Andy Little