"Eric Lemings" <lemings@roguewave.com> wrote in message news:D730FF7CEDDCA64483F9E99D999A158B476D82@qxvcexch01.ad.quovadx.com...
-----Original Message----- From: boost-bounces@lists.boost.org [mailto:boost-bounces@lists.boost.org] On Behalf Of Andy Little Sent: Wednesday, August 23, 2006 10:15 AM To: boost@lists.boost.org Subject: Re: [boost] Boost Units library preview
"Phil Richards" <news@derived-software.ltd.uk> wrote in message news:20060823145751.6C0A0AABB8@derisoft.derived-software.demon .co.uk...
On 2006-08-23, Matthias Troyer <troyer@itp.phys.ethz.ch> 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