Ezra,
Is now the time to switch from Google to Firefox to avoid that single
(isolated, unique, I hope) backward-minded advocate of American units in your
organization? Place a copy of NIST SP 811 at his work station and see if he
deserves to remain your friend? Is he really from the top
Generally, I like it. I have a few comments, though. The first couple won't
be too controversial.
Is the little anecdote about lengthening stride to 1 m realistic? I'm 1.94 m
tall, and my natural stride is about 0.9 m. Marching against a grid, I can
stretch it out to 0.9144 m (yes, you
Pat,
Åfter you have made the *improvements* explicitly noted (and implied) in John
Steele's critique of your Millimeter School please post it again for review.
I side with Jim and John that the Optimal School should teach centimeters in
grades K-2 (with some upward flexibility for gifted
I just received Metrication Matters 93, and saw the aircraft hanger example
again. As it is snow season in the US, and people need to worry about their
roofs, I have to point out two huge errors in the example as I don't believe
anyone should rely on that example.
80 cm of snow != 8 mm of
Congressmen, Senators, Committee Chairman, Members, staff:
Here is something that is directly related to the success of the USA, and is
the foundation of all trade, science, technology, engineering and math
(STEM) - implement SI metric across the country. Take away the voluntary
provisions in
If anybody is worried about their roofs, please use at least 320 kg/m³ for wet
snow on sloped roofs. If you have a flat roof, determine whether the drain is
working, it will be the difference between 320 kg/m³ wet snow and 960 kg/m³
slush.
I believe that those figures assume an accumulation
Ezra, the counter-rejoinder to your colleague is that there are no
American units! What we use for units in the U.S. are based upon the
metric system. Show him http://www.metric.org/laws/mendenhall.html
Paul
Paul Trusten, R.Ph. , Vice President
U.S. Metric Association, Inc.
www.metric.org
Isn't the *residual* load at any moment the critical measurement, or its
slightly delayed accumulated distortion (strain, displacement) of roof trusts?
Load can be measured as mass per unit area, or force per unit area (stress),
independent of its state, water plus melted snow of any *initial
Jim,
It is a density, and based on a specific condition of snow, but not on depth.
It needs to be multiplied by depth.
Like any density, it is dependent on the material meeting the condition. It is
based on fully saturated but draining snow (basically it needs to be melting).
However, I
You're right, of course, John.
My eyes misread those tiny subscripted 3s as 2s and I thought you were
giving figures of mass divided by area.
I apologize for misreading your posting.
Jim
On 2011-02-09 1621, John M. Steele wrote:
Jim,
It is a density, and based on a specific condition of
If the snow depth is reduced to a melted equivalent, at least you know what
density to multiply by. Otherwise, it is the depth de jour times density de
jour.
My point was that the hanger was loaded to a MUCH higher stress than
calculated, and that the calculation, with either the 8 mm or 80
Thanks Gene,
I will consider your remarks and adapt the text accordingly.
My plan is to consider all critiques from knowledgeably people such as UKMA and
USMA list members and then post it on the Metrication matters website.
Cheers, and thanks again,
Pat Naughtin
Geelong, Australia
On
Thanks -- again -- John,
This is the third time that this arithmetical error escaped my clutches.
I will repair the damage on the archived copy on the website, and do some
serious grovelling in the next issue of the Metrication matters newsletter.
Cheers and thanks again, and again, and again,
Thanks Jim,
I will use your data when I correct the other error. I have to say that I have
been uncomfortable with the 10 times approximation between snow and ice as
being too trite. Can I plead ignorance as we in Australia don't see a lot of
snow unless we travel to our few mountains. Our
Dear John,
I found this reference in my travels:
http://www.grc.nasa.gov/WWW/k-12/WindTunnel/Activities/fluid_pressure.html
It looks like approximated the pressure due to the water and forgot to add the
effect of the air pressure. I will reconsider and correct.
Cheers and thanks again for
Air pressure would not be relevant in the hanger example as it acts on both
sides, and has no net effect.
In the pressure data in your Optimal School, it may matter, but it depends on
the nature of the analysis and whether you need absolute or gauge pressure in
calculations.
--- On Wed,
Dear All,
Another interesting article on the economics of non-metrication:
http://chronicle.com/blogs/brainstorm/convert-then-compete/31953
Cheers,
Pat Naughtin LCAMS
Author of the ebook, Metrication Leaders Guide, see
http://metricationmatters.com/MetricationLeadersGuideInfo.html
Hear Pat
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