Re: [boost] Boost Units library preview

From: Andy Little (andy_at_[hidden])
Date: 2006-08-23 12:33:15

"Eric Lemings" <lemings_at_[hidden]> wrote in message 
news:D730FF7CEDDCA64483F9E99D999A158B476D82_at_qxvcexch01.ad.quovadx.com...
>
>
>> -----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?

Aha I'll try that next. Darn rusty bolts ! :-)

regards
Andy Little