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

"Phil Richards" <news_at_[hidden]> wrote in message
> 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 ! ;-)

Andy Little

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