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**J. Clarke[_2_]** · July 17th 13, 07:50 PM posted to rec.photo.digital.slr-systems

In article 2013071710180710672-savageduck1@REMOVESPAMmecom,
says...

On 2013-07-17 09:48:44 -0700, "J. Clarke" said:

In article 2013071708363558821-savageduck1@REMOVESPAMmecom,
says...

On 2013-07-16 21:44:28 -0700, "J. Clarke" said:

In article ,
says...

On 2013.07.06 11:05 , J. Clarke wrote:
In article ,
says...

On 2013.07.03 22:28 , J. Clarke wrote:
In article ,
says...

On 2013.07.03 20:38 , J. Clarke wrote:

The trouble with the metal straps is that things like scooter grabs can
be turned from loss of property into serious injury. With luck it will
be injury of the grabber who gets pulled off the scooter and into the
path of an oncoming lorry. Personally my luck runs more in the
direction of me being pulled into the path of the lorry.

The person on the scooter is in a much more unstable position than a
person walking or standing. OTOH the crafty buggers probably feel the
resistance and abandon within a shake of a lamb's tail.

The scooter's 2 up and gyrostabilized--you've got anywhere from 400-1000
pounds of mass going for you depending on the value of "scooter".

In Asia the people doing the grabbing generally mass about 50 - 60 Kg.

That's the passenger. The "driver" is another 50-60kg.

The scooter can keep on going but he's not going with it. And as I
said, as soon as the strap doesn't cut and there is resistance he's just
going to let that one go.

Who said anything about "cut"?

Oh, so you know nothing about how these guys work. I've seen it done
and it's slow down, bump, cut, grab and run (or ride).

If you have a steel cable strap it's:
slow down, bump, cut - Ooops - run (or ride).

(A pound is not "mass").

Now you are being pedantic, and ignorant as well. A pound mass is
approximately 1/32 of a slug.

You lost when you mixed pounds and mass. A slug is mass. A pound is
force. There is no mixing them.

That would be news to the faculty and staff in the Aeronautical
Engineering department at The Ohio State University, in the Mechanical
Engineering department at The Georgia Institute of Technology, the
engineering staff at United Technologies, the national standards bodies
of the United States, Canada, New Zealand, the United Kingdom, South
Africa, and Australia, which have established an international standard
defining the avoirdupois pound as 0.45359237 kilogram, and a variety of
other degreed engineers and scientists of my acquaintance.

Sorry, but you are not only being pedantic, but now you are being
stupidly pedantic.

OK! Let's get pedantic.

Why? Pedants are boring and waste everybody's time with pointless crap.

What the man in the street thinks of as "weight" and mass are two
different things. "Weight" expressed in "pounds" is not the same as
mass expressed in "pounds".

So what? The assertion is that the pound is not a unit of mass. That
assertion is simply wrong. The pound is defined by the NIST and the
equivalent standards bodies of many other nations as being 0.45359237
kilogram. It is not defined as being so many "Newtons" and it is not
defined as being so many "Dynes" and it is not defined as being so many
of any other unit of force, it is defined in units of mass.

Re-read what I wrote. You might see that I spoke of the misconception
that the unit of mass "the pound" is commonly interpreted by those
ignorant of physics as "weight" which is indeed an expression of force.

You can argue with me until Hell freezes over and that won't change
anything because I am not the one who sets the standards. If you
believe that the pound is necessarily a unit of force and not a unit of
mass, you really need to take that up with the standards bodies.

The force known as "weight" (Lb., Kg, etc.) is a force proportional to
mass and acceleration. So other than dealing with mass v "weight" in
different gravitational acceleration fields (Earth v. Moon) you have to
go to Newton and the 2nd Law of Motion and the concept of inertial
acceler. So "weight"= (mass)(acceleration), or W=mg

Which has zip all do to with the definition of a pound.

So given the difference of gravitational acceleration on Earth and the
Moon, a man with a 100Kg mass will show two different weights if his
mass is measured with a spring scale on the Moon, to that on Earth.
However, if a balance beam mass scale is used his mass will be equal
(100Kg) on both Earth and Moon.

Which still has zip all to do with the definition of a pound.

In the case of the "scooter snatch" there is inertial mass to be
overcome (the mass of the bag carrier). there will be several possible
results in a "scooter snatch" attempt where the strap is not cut.
1: the bag is separated from the carrier.
2: the bag and the carrier are unable to overcome the force imposed by
the acceleration of the scooter and are dragged.
3. the snatcher on the scooter is unable to overcome the inertial force
of the mass of the bag carrier, and is pulled from the accelerating
scooter.

Which is true whether you measure mass in pounds, slugs, kilograms,
abuchi, or wiardunek, so it has absolutely nothing to do with the
definition of a pound.

Both the carrier and the snatcher are subject to the inertial force
applied by the acceleration of the scooter, and physics will determine
which will prevail once surprise is taken out of the equation.

Which still has zip all to do with the definition of a pound.

For most folks "weight" is the force on an object required to overcome
gravity. So strangely enough a mass in free fall is weightless until
its inertia cannot overcome gravity. i.e. the instant it touches the
surface of the body exerting gravitational attraction. That is why an
individual with a 100Kg mass can experience weightlessness while flying
in NASA's "vomit comet". effectively he/she is in free fall while
retaining a weightless mass.

Which still has zip all to do with the definition of the pound.

A slug is an Imperial unit of mass, not weight.

Since the definition of the slug was not at issue, this comes under the
heading of irrelevant trivia.

Look, Duck, I got my physics degree in 1975 and my engineering degree in
1979 and a piece of hardware I worked on succesfully entered the
atmosphere of another planet in 1995.

So what? I don't have a degree in physics, but I certainly have an
advanced education in physics provided at Syracuse some time before
your 1975 graduation.

When I say that the pound is a unit of mass, I am not expressing an
uninformed opinion, I am telling you what is taught in engineering and
physics programs, and used in real-world engineering, based on having
successfully completed such programs and successfully engaged in real-
world engineering.

Where did I disagree with that? A pound is certainly a unit of mass.
The misconception is equating "weight" with mass, thereby confusing
units of mass (pounds, Kg, slug, etc) with weight. That as I have
stated is a force. So, if you took a less argumentative stance you
might have noticed that I am in agreement with you regarding calling
pounds a force or a mass. The pound is without doubt a unit of mass.

Sorry for misinterpreting your intent, however the original argument was
one over nomenclature, not over the understanding of weight and mass.