>>> Not likely since Kg is not a measure of force.

>> PICy picky :-).
>> While that is strictly true, there are many exceptions to
>> such general usage that allow such nominally "lazy"
>> statements to be made in polite and even informed 
>> company.

> Made yes, and hanging someone for making such statements 
> would be out of
> bounds, but criticism is certainly justified. IM(H?)O 
> criticizing such
> criticism is [self-censorship kicks in].

You are being, for you, unusually inconsistent :-). I KNOW 
you know what you are talking about and I understand your 
point. But it is in practice violated in everyday use in 
much of the world to the extent that people are unaware of 
the "correct" usage at almost all levels. Weighing units 
whose mechanism works by measuring force MAY be calibrated 
in mass units on their scale (although a vast number are not 
*) but they MEASURE force, as you know. One could argue that 
a mass/mass balance is a mass measurer as the two masses 
generate forces which are related by the (almost) common 
gravity field that they reside in, as I know you know. A 
rare example of a true mass measurer is the Space Shuttle's 
astronaut weigher which uses AFAIR period of oscillation of 
an arm to determine mass. * Pounds are not, as I know you 
know, units of mass. Even pounds-mass are not a real unit 
(he said dangerously). The real unit is, as I said and as I 
know you know, the slug which is the mass which "weighs" g 
pounds or about 32 pounds. I have yet to see a mass 
measuring device, or a force measuring device, calibrated in 
slugs, but there are countless many calibrated in the force 
unit pounds, which is the force exerted in a one g field by 
the non existent 1 pound mass. ie in the imperial system the 
overwhelming common usage is to use force units to represent 
both mass and force, and only a scientist, an engineer or a 
pedant does otherwise. (I being all 3 ... ;-) ).
For the mksa / SI system the opposite everyday convention 
applies and the norm is for both mass and force to be 
commonly represented by mass units, leaving poor old Sir 
Isaac to the realm of aforesaid scientists, engineers and 
pedants. (I being all 3 ...). Which is where we came in.

>> And, properly, one should ask for sold-by-weight material 
>> by
>> it's force value rather than it's mass.

> no, definitely by its mass. weighting instruments used are 
> calibrated to
> read the mass *at the place they were calibrated*, so 
> nothing wrong with
> asking for mass. It even prepares for interstellar trade.

As above.
Slugs just don't cut it.

And re my discourse on Isp. That argument really has gone on 
for decades and is unlikely to ever be resolved. In that 
case it's almost only the pedants who get it "correct". Some 
give up, multiply Isp by g and call it exhaust velocity. 
Which it sort of is, but it is far less evocative.

> Glimpse from my 6-y old son trying to understand our 
> sometimes confusing
> world: kilo is a synonym for 1000, as in km. but it is 
> also a synonym
> for 1000g. He is (rightly?) blaming the world for being 
> illogical. He is
> in for an interesting life.

Indeed :-)


        Russell

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist