## PSN-L Email List Message

From: ian ian@...........
Date: Mon, 10 Apr 2006 16:25:44 +0100

```agreed.  The spring type of weighing machine though is, I believe, in
the majority given their advantage of not needing weights.  My last
email assumed the use of the spring type weighing machines.

Ian

James Hannon wrote:

>There are actually two types of "weighing machines" scales. One uses springs and actually measures force. The other is a balance which compares one mass against another. This type of scale will be accurate in measuring mass as long as there is any gravity at all.
>
>---------- Original Message ----------------------------------
>From: ian
>Date:  Mon, 10 Apr 2006 16:11:58 +0100
>
>
>
>>yes, mass is a constant which is the nice thing about it.
>>
>>Sorry to bring this discussion here, apologies in advance.
>>
>>The problem is that mass and weight are different concepts.  When we buy
>>a quantity of goods, like flour for instance, we put the flour on a
>>weighing machine, which measures the weight but, under the metric
>>system, we quote the weight in units of mass (Kg).
>>
>>Now if we buy 10 Kg of flour in Reykjavik then take it and the measuring
>>machine to Panama and measure out another 10 Kg, we will find that the
>>two 10 Kg bags of flour are different (by a tiny amount).  This takes us
>>back to the original (correct) premise that mass does not vary and so
>>there is something wrong with our experiment.
>>
>>The something wrong is that we used a weighing machine (instead of a
>>"massing" machine) and implicitly applied a constant to convert the
>>weight into mass.  The constant is the thing that varies with where you
>>are on the Earth and mainly consists of the acceleration due to the
>>Earth's gravity, minus the centrifugal force caused by the Earth's
>>spin.  Both contributions vary around the globe.
>>
>>Again, apologies for the non-quaky topic.
>>
>>Ian
>>
>>Barry Lotz wrote:
>>
>>
>>
>>>Hi All
>>> If I remember my physics, mass does not vary with location (unless
>>>you are traveling very fast) but force does ( f=m*a) . the earths
>>>acceleration does vary with location.
>>>regards
>>>Barry
>>>
>>>
>>>ian  wrote:
>>>
>>>    at the risk of religious wars(!), the "kilo" is subject to
>>>    variation from place to place because we use a weighing machine to
>>>    measure it!
>>>
>>>    Sigh.
>>>
>>>    :-)
>>>
>>>    Ian
>>>
>>>
>>>    ChrisAtUpw@....... wrote:
>>>
>>>
>>>
>>>>    In a message dated 04/04/2006, ian@........... writes:
>>>>
>>>>        the comparrison is deeply flawed.  A metric tonne is a unit
>>>>        of mass, a ton is a unit of force. Someone screwed up
>>>>        significantly when we went metric. It should have been
>>>>        Newtons or Kilo-Newtons for measuring weight.
>>>>
>>>>        Ian.
>>>>
>>>>    Hi Ian,
>>>>
>>>>        No, it should not be defined as the force. If it were, the
>>>>    actual quantity (mass) would vary from place to place. The ton in
>>>>    commerce is also mass. Going metric wasn't a 'screw up'?
>>>>
>>>>        Regards,
>>>>
>>>>        Chris Chapman
>>>>
>>>>
>>>
>>>
>>
>>
>
>--
>Jim Hannon
>http://www.fmtcs.com/web/jmhannon/
>42,11.90N,91,39.26W
>WB0TXL
>--
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with
>the body of the message (first line only): unsubscribe
>
>
>
>

agreed.  The spring type of weighing machine though is, I believe, in
the majority given their advantage of not needing weights.  My last
email assumed the use of the spring type weighing machines.

Ian

James Hannon wrote:

There are actually two types of "weighing machines" scales. One uses springs and actually measures force. The other is a balance which compares one mass against another. This type of scale will be accurate in measuring mass as long as there is any gravity at all.

---------- Original Message ----------------------------------
From: ian <ian@...........>
Date:  Mon, 10 Apr 2006 16:11:58 +0100

yes, mass is a constant which is the nice thing about it.

Sorry to bring this discussion here, apologies in advance.

The problem is that mass and weight are different concepts.  When we buy
a quantity of goods, like flour for instance, we put the flour on a
weighing machine, which measures the weight but, under the metric
system, we quote the weight in units of mass (Kg).

Now if we buy 10 Kg of flour in Reykjavik then take it and the measuring
machine to Panama and measure out another 10 Kg, we will find that the
two 10 Kg bags of flour are different (by a tiny amount).  This takes us
back to the original (correct) premise that mass does not vary and so
there is something wrong with our experiment.

The something wrong is that we used a weighing machine (instead of a
"massing" machine) and implicitly applied a constant to convert the
weight into mass.  The constant is the thing that varies with where you
are on the Earth and mainly consists of the acceleration due to the
Earth's gravity, minus the centrifugal force caused by the Earth's
spin.  Both contributions vary around the globe.

Again, apologies for the non-quaky topic.

Ian

Barry Lotz wrote:

Hi All
If I remember my physics, mass does not vary with location (unless
you are traveling very fast) but force does ( f=m*a) . the earths
acceleration does vary with location.
regards
Barry

ian <ian@...........> wrote:

at the risk of religious wars(!), the "kilo" is subject to
variation from place to place because we use a weighing machine to
measure it!

Sigh.

:-)

Ian

ChrisAtUpw@....... wrote:

In a message dated 04/04/2006, ian@........... writes:

the comparrison is deeply flawed.  A metric tonne is a unit
of mass, a ton is a unit of force. Someone screwed up
significantly when we went metric. It should have been
Newtons or Kilo-Newtons for measuring weight.

Ian.

Hi Ian,

No, it should not be defined as the force. If it were, the
actual quantity (mass) would vary from place to place. The ton in
commerce is also mass. Going metric wasn't a 'screw up'?

Regards,

Chris Chapman

--
Jim Hannon
http://www.fmtcs.com/web/jmhannon/
42,11.90N,91,39.26W
WB0TXL
--
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To leave this list email PSN-L-REQUEST@.............. with
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