Loaded test question!!!

[david luchini]

So I'm supposed to comment on your posts while you ignore the better part of mine... :roll:

So I'll take that as a No, P = H * D wouldn't give the pressure at the base of the cylinder in my example.:grin:

Close enough? Well taken that the all time percentage of objects weighed in places much, much closer to Earth's mean radius versus atop Mt. Everest, I'd guess the ratio to be astronomical.

So if the result would be close enough "most of the time" you'd just ignore the other times? I wouldn't

So do you also account for g-force deviation due to lattitude and the angle of g-force?

Yes, of course. Acceleration is a vector. It has not only magnitude but direction.

In a weighing of product, do you continually compensate for air bouyancy?

I don't have much call for weighing of product (I've never tried to weigh an electron) but I'd think you don't need to compensate for air buoyancy. If the air is more buoyant, the object would weigh less. If the air is less buoyant, then same object would weigh more. More evidence that acceleration must be included into the equation for pressure.

You do know the federal trade definition of a pound weight is within a vacuum, right?

I had no idea, and couldn't find any such definition on FTC.gov. Maybe its true, but it just goes to show if the FTC is that precise about the weight of a pound, then "close enough" probably isn't good enough for them.

When is the last time you checked the gravitational force at your location?

Never have. How about you?

 

[Smart $]

...

When is the last time you checked the gravitational force at your location?

Never have. How about you?

I never have either... and this is the summation of my point, and the ultimate pitfall to the premise of your argument. You emphasize local adjustment as a necessity, but yet you do not practice what you preach.

If this was such a major concern, don't you think there would be online information about practically every populated location throughout the world? I looked and didn't find anything more than for a few major cities. Perhaps you can do better.

 

[Smart $]

...

Close enough? Maybe. The same? No.

For your entertainment...

http://www.calpoly.edu/~gthorncr/ME236/documents/AccuracyofGravity.pdf

http://www.ngs.noaa.gov/cgi-bin/grav_pdx.prl

 

[david luchini]

I never have either... and this is the summation of my point, and the ultimate pitfall to the premise of your argument. You emphasize local adjustment as a necessity, but yet you do not practice what you preach.

I don't emphasize any "local adjustment" as a necessity, I emphasize ACCELERATION as a necessity.

Force = Mass x ACCELERATION

Pressure = Mass x ACCELERATION/area

Would the pressure at the base of the cylinder still be calculated by P = H * D? Of course not. You'd be off approx. 18%. Add "acceleration" back into the equation: P = H * D * a, and you'd have a complete equation.

The ultimate pitfall of your argument is that by ignoring ACCELERATION so that you can leap to Force ≈ Mass, you'd provide a solution that is not nearly "close enough" but is way off, in the example above.

 

[Smart $]

I don't emphasize any "local adjustment" as a necessity, I emphasize ACCELERATION as a necessity.

Force = Mass x ACCELERATION

Pressure = Mass x ACCELERATION/area



The ultimate pitfall of your argument is that by ignoring ACCELERATION so that you can leap to Force ≈ Mass, you'd provide a solution that is not nearly "close enough" but is way off, in the example above.

Come now, do you really think I would apply lb(Force ≈ Mass) where it does not apply??? :roll:

 

[Besoeker]

Taken out of context, it sure seems that way


Within the context of my comment and the discussion on my part, places on earth where gravitational force is at its extreme, on the moon, or in space are most certainly are excluded from the other side of a leapt chasm.

What force will give a mass of 1lb an acceleration of 1 ft/s^2?

 

[Smart $]

What force will give a mass of 1lb an acceleration of 1 ft/s^2?

Talk about loaded questions :roll:

1 lbm-ft/s?

Again, out of context...

Come now, do you really think I would apply lb(Force ≈ Mass) where it does not apply??? :roll:

 

[david luchini]

1 lbm-ft/s?

Yes! The Poundal rears its ugly head.:grin:

 

[david luchini]

What force will give a mass of 1lb an acceleration of 1 ft/s^2?

Besoeker, 5 months till the Ashes - who do you think will prevail? (Or don't you follow the game.)

 

[LarryFine]

So, do the A's still have it, or are we still less than convinced?

 

[Besoeker]

Besoeker, 5 months till the Ashes - who do you think will prevail? (Or don't you follow the game.)

It doesn't greatly interest me. Maybe if I was English it might.
But probably not.

 

[gadfly56]

What force will give a mass of 1lb an acceleration of 1 ft/s^2?

That would be 1/32.174 lbf. In the FPS system, the unit of mass is the slug. So one pound force provides an acceleration to one slug of one foot per second per second. If that slug is sitting on the face of the earth where the local acceleration field is 32.174 ft/sec^2, a scale calibrated for lbf will read a "weight" of 32.174. So if you use a spring scale and dangle an object from it and it "weighs" one pound, it's mass is about 0.0311 slugs, or coincidently, one poundal.

 

[Besoeker]

Talk about loaded questions :roll:

1 lbm-ft/s?.

Isn't it about 0.031 lbf?

 

[gadfly56]

Isn't it about 0.031 lbf?

Didn't I say that in #92 :-??

There is obviously a real problem with terminology here, especially using "pound" to indicate mass and weight. A object that "weighs" 100 pounds exerts a force, as measured by a scale located in an acceleration field of 32.174f t/sec^2, of 100 pounds. It does NOT have a MASS of 100 pounds because "pound" is not a unit of mass in the FPS system of measurements, nor any other. Technically I do not "weigh" 200 pounds (again, I wish :grin, I exert a force on the earth of 200 pounds in a gravitational field of 32.174 ft/sec^2.

 

[Smart $]

Isn't it about 0.031 lbf?

Yes... but what's your point?

 

[Smart $]

So, do the A's still have it, or are we still less than convinced?

I believe the A's have it, if my memory serves me well

...it's been a while since we were actually on topic

 

[Besoeker]

Didn't I say that in #92 :-??

Yes, but it wasn't there when I started to post.

There is obviously a real problem with terminology here, especially using "pound" to indicate mass and weight.

I agree.

 

[Besoeker]

Yes... but what's your point?

To obtain that result you have to take account of the gravitational constant.

 

[Smart $]

To obtain that result you have to take account of the gravitational constant.

Of course! ...the force acting upon the mass is something other than [Earth's] gravity. With pound-force defined by Earth's gravitational force, its magnitude has to be part of any conversion to a force of different magnitude. I believe I already mentioned in the context of my earlier posts, lb(force ≈ mass) is only appropriate when [Earth's] gravity is the only force acting upon the mass.

 

[mivey]

In the FPS system, the unit of mass is the slug.

But the mass of a slug can change, especially if exposed to salt.