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Mass vs inertia



 
 
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  #1  
Old November 5th 05, 01:57 PM
Double-A
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Default Mass vs inertia


Don1 wrote:
KeithK wrote:
"Don1" wrote in message
oups.com...
Don1 wrote:
Mass is an unspecific body of matter. Inertia is the specific measure
of the force (f) exerted on, and/or by a body of matter, to the rate of
displacement (s/t) that it causes; where ft/s is a constant.

Mass is the specific measure of the impulse - the product of force (f)
and its duration (t) - exerted on, and/or by a body of matter, to the
rate of displacement (s/t) that it causes;


OK, that's better, although a bit unorthodox in viewpoint.
It's not usually stated that way, and it would be a tricky method
for measuring the numeric value of an object's mass, but the implied
equation works, assuming F is the force applied to an object of
mass M, T is the duration of the applied force, and s/t = V is the
object's resultant change in velocity:

It's usually written as the 'Impulse Equation':
F*T = M*V
where F*T is the Impulse applied to an object at rest, and M*V is the
resultant change in Momentum.

You write it your way; but I'll write it as ft=s/t; which makes it a
constant: Which is ft^2/s, for any given body, and is equal to 2w/g.

But I have to agree, one could conceivably determine an object's mass
by whacking it with a hammer, measuring how many microseconds
the whack lasted, and the average force, and observing it fly off the table.

It would be easier Keith, to just read the weight from a weight scale,
and divide that weight by g/2. That will determine the object's mass.



Don,

How do you calibrate your handy weight scale to read the correct lbf
force?

Most everyday scales are adjusted so that when you put 1 lbm on the
pan, it reads one.

But as a practical matter, how do you apply a standard force so that 1
lbf will read exactly 1 on the scale?

Double-A

  #2  
Old November 5th 05, 05:41 PM
Don1
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Default Mass vs inertia

Double-A wrote:
SNIP
Don,

How do you calibrate your handy weight scale to read the correct lbf
force?

Most weight scales are _already_ calibrated to that effect and will
last for years.

Most everyday scales are adjusted so that when you put 1 lbm on the
pan, it reads one.

What is a lbm? Isn't it an object, or mass of matter that weighs 1 lbf
?

But as a practical matter, how do you apply a standard force so that 1
lbf will read exactly 1 on the scale?

There is no standard force. Force is a variable; as is weight: Where a
body's weight varies depending on where it is weighed. The important
thing to do, to get honest accurate results when weighing, is to set
the adjustment to read zero before each use; when the scale is empty.

If you are _really_ gung-ho you could make your own "Double-A" weight,
but it would be expensive! and an awful lot of work. My advice is to
follow along with all the work that's already been done with the
pound-force.

Double-A


  #3  
Old November 5th 05, 06:20 PM
G=EMC^2 Glazier
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Default Mass vs inertia

Don Weight and mass are not the same thing. You weigh 6 times less
onthe oout your mass is the same every where in the universe as long as
the mass is on the outside of a BH horizon. Bert

  #4  
Old November 5th 05, 06:26 PM
Herman Trivilino
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Default Mass vs inertia

"Don1" wrote ...

What is a lbm?


You know perfectly well that a pound of mass is, by definition, 0.453 592 37
kg.

Isn't it an object, or mass of matter that weighs 1 lbf


No. Which you also know, very well.

Pretending again, huh?

But as a practical matter, how do you apply a standard force so that 1
lbf will read exactly 1 on the scale?


There is no standard force. Force is a variable; as is weight:


Quantities that vary need a standard to define them. Without the standard,
there is no way to define one unit of force!



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  #5  
Old November 5th 05, 06:47 PM
Don1
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Default Mass vs inertia

Herman Trivilino wrote:
Snip

Quantities that vary need a standard to define them.


Yes like a weight-scale, a ruler, or a tape, or at least a computer.

  #6  
Old November 5th 05, 07:50 PM
Herman Trivilino
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Default Mass vs inertia

"Don1" wrote ...

Quantities that vary need a standard to define them.


Yes like a weight-scale, a ruler, or a tape, or at least a computer.


No. These are not examples of standards used to define quantities that
vary.



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  #7  
Old November 5th 05, 07:54 PM
Herman Trivilino
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Default Mass vs inertia

"Don1" wrote ...


Quantities that vary need a standard to define them.


Yes like a weight-scale, a ruler, or a tape, or at least a computer.


You could use a weight scale to measure force, but to calibrate that scale
you'd need a standard.

(The little wheel that you turn to zero a scale doesn't calibrate it).




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  #8  
Old November 5th 05, 09:46 PM
Don1
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Herman Trivilino wrote:
Snip

(The little wheel that you turn to zero a scale doesn't calibrate it).

I know, but it's important purpose is that it zeros it in for each use:
How often does a scale really need to be calibrated, unless it gets
knocked out of whack? Then call in the "bureau of weights and
measures". They have the weights and measures to check the calibration
any scale.

  #9  
Old November 5th 05, 11:58 PM
Herman Trivilino
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Default Mass vs inertia

"Don1" wrote ...

I know, but it's important purpose is that it zeros it in for each use:
How often does a scale really need to be calibrated, unless it gets
knocked out of whack?


Once. When it's built.

Then call in the "bureau of weights and
measures". They have the weights and measures to check the calibration
any scale.


Yes, they do.

So, it seems you can see the importance of having a standard with which to
calibrate the scale.

Without it, there is no way to manufacture the scale in the first place.



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  #10  
Old November 6th 05, 12:18 AM
Don1
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Default Mass vs inertia

Herman Trivilino wrote:
"Don1" wrote ...

I know, but it's important purpose is that it zeros it in for each use:
How often does a scale really need to be calibrated, unless it gets
knocked out of whack?


Once. When it's built.

Then call in the "bureau of weights and
measures". They have the weights and measures to check the calibration
any scale.


Yes, they do.

So, it seems you can see the importance of having a standard with which to
calibrate the scale.

Without it, there is no way to manufacture the scale in the first place.

Oh sure. We could choose any standard weight, but like I said to Double
A, it would be expensive to start all over again. Might as well go
along with the pound-force, and weight that we have now. A lot of
research and developement has gone into it.

 




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