I would be interested to know in what university Robert Wyatt was
educated in physics. His pound, which he insists is a unit of force,
has a less value in Denver than in boston. Some unit! He wrote in
USMA 25386:
At 8:02 PM -0500 3/20/03, Joseph B. Reid wrote:
Robert T. Wyatt in USMA 25232 a common misconception among engineers.
A little high school lesson regarding Han's points:
I'm rather uncomfortable with the obfuscation and lax use of the
terms "weight" and "mass."
A "pound" is not a unit of mass, it is a unit of weight, which is
a specific form of force. In fact, force is mass multiplied by
acceleration and in the case of a pound it would be 1 slug x 32
ft/s2.
The equivalent metric unit is the Newton, where one Newton equals
one kilogram accelerated at 9.8 meters per second squared.
Without such basic concepts, nomenclature is pointless.
Robert would expect to get more butter in a pound in Denver than in
Boston because thw acceleration due to gravity is less in Denver
than in Boston.
This is patently absurd. I would expect the scales to be calibrated
so that the local acceleration due to gravity is corrected for.
This is precisely the difference between mass and force when
discussing weight.
If one were to use a balance as opposed to a scale, then there would
be no calibration necessary.
ie: 1 slug in Boston = 1 slug in Denver or, if you prefer (as I
do), 1 gram in Boston = 1 gram in Denver.
And, yes, I confess to being educated as a physicist as you point out below.
The British and the Canadian Weigths and Measures Acts both
define the poound as a unit of mass, not a unit of weight. The
aeronautical engineer's unit of mass is the slug = 32.2
pounds-mass. Victorian physicists solved the linguistic problem by
recognizing the pound as a unit of mass but the poundal as a unit
of force:
32.2 poundals = 1 pound-force
Physicists recognize Newton's First Law of Motion as
force (newtons) = mass (kilograms) X acceleration (metres/second^2)
Engineers have to say:
force (pounds) = mass (pounds) X acceleration (feet/second^2)/32.2
When Canada went metrtic an elderly Professor of Mechanical
Engineering at McMaster University, Hamilton, taught that under the
metric system Newton's First Law was only true at a point in space
where the acceleration due to gravity is 1 metre per seond squared.
--
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
--
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
