Mass vs Mass as a Force (Weight)

[A.T.]

Because the general public is ignorant of how the word "weight" is used by people knowledgeable of physics, it gets used with other meaning on a daily basis.

It should be noted, that it's usually not the public that takes words from physics, and uses them wrong. It's physics that takes general words from common language (where they are sometimes already have multiple meanings), and uses them for some very specific physics concepts (sometimes also ambiguously).

 

[Digcoal]

Why is that irrational?

We are having this discussion, aren’t we?

I’m not the one that started this thread, and it’s perfectly valid for this thread to have been started considering the illogic of using “weight” to mean mass sometimes and force at other times.

I mean, they seem to have compounded it by distinguishing between pound-mass and pound-force. Whoever thought THAT was a good idea probably doesn’t spend much time interacting with the general public.

 

[Digcoal]

It should be noted, that it's usually not the public that takes words from physics, and uses them wrong. It's physics that takes general words from common language (where they are sometimes already have multiple meanings), and uses them for some very specific physics concepts (sometimes also ambiguously).

No argument here.

It’s not just physics, and it happens quite a bit as knowledge increases at an exponential rate. We are learning things faster than we, apparently, have time to coin new words for.

I have no problem adding definitions to established words. I am merely stating that that illogical process of overloading words with meanings causes threads like this to occur. It is natural for the brain to join similar ideas together, but if you don’t create proper distinctions, you get these conversations.

Scientists and mathematicians are seldom linguists/neurologists.

 

[pbuk]

Weigh and weight and weightless are all used differently within the same field of study.

What field of study are you talking about?

 

[pbuk]

I am merely stating that that illogical process of overloading words with meanings causes threads like this to occur.

Why do you think that that point is not obvious to anyone else? What do you think could be done to improve the situation?

 

[Digcoal]

Why do you think that that point is not obvious to anyone else? What do you think could be done to improve the situation?

Same as learning anything else new: one arduous step at a time. Change always happens, it’s just that many processes evolve over longer timescales than the lifespan of humans or even societies.

Accepting that it is illogical is the first step. Accepting that something is wrong is always the first step to solving any problem. Problems are nothing more than the difference between two states of being. Solutions are the path between those two states. This is true in math/science as well as in personal/political issues.

 

[Digcoal]

What field of study are you talking about?

The one that relates them in the same equation: F = m • a

weight (force) = weight (mass) • acceleration (gravity)

 

[pbuk]

Accepting that it is illogical is the first step. Accepting that something is wrong is always the first step to solving any problem.

OK, I think everyone that understands the concept of mass accepts that using the word "weight" to describe a mass is illogical.

What is the next step?

This is true in math/science as well as in personal/political issues.

Can we clarify that there is no inconsistent use of 'weight' and similar terms in math/science? Your posts are confusing to me because it is not clear that you accept this.

 

[pbuk]

The one that relates them in the same equation: F = m • a

weight (force) = weight (mass) • acceleration (gravity)

That is wrong. Where have you seen that equation described that way?

 

[Digcoal]

OK, I think everyone that understands the concept of mass accepts that using the word "weight" to describe a mass is illogical.

What is the next step?Can we clarify that there is no inconsistent use of 'weight' and similar terms in math/science? Your posts are confusing to me because it is not clear that you accept this.

What is there to accept: that “weight” is used in two different places within the same equation with distinctly different dimensions?

Yeah. I have not denied that “weight” is consistently used illogically.

 

[Digcoal]

That is wrong. Where have you seen that equation described that way?

Are you now denying that “weight” is NOT used to denote mass in some cases and gravitationally induced force in others?

Edit: But to answer your question more directly: 32 pounds-force = 1 pound-mass • 32ft/s^2

 

[pbuk]

Are you now denying that “weight” is NOT used to denote mass in some cases and gravitationally induced force in others?

No I am not. Now please answer my question. (Edit: pausing to reconsider double negative).

 

[Digcoal]

No I am not. Now please answer my question. (Edit: pausing to reconsider double negative).

I added the more direct answer to my original response.

(Edit: double negatives make discourse clunky like overloading definitions does, aye? )

 

[pbuk]

Are you now denying that “weight” is NOT used to denote mass in some cases and gravitationally induced force in others?

Yes I deny that weight is not used inconsistently. Eliminating two out of the three negagives to reduce confusion: I agree that weight is used inconsistently. I think that we can all agree on that. Where there is a disagreement is that you assert that weight is used inconsistently in science; I assert that it is not: in science weight is always a force, however one example of inconsistent use is between science and commerce where weight is often used to describe a measure of mass.

But to answer your question more directly: 32 pounds-force = 1 pound-mass • 32ft/s^2

Answering questions directly is a good way of avoiding confusion: now I can see where you are confused.

• In science we do not use pounds and feet any more, we use SI units.
• In engineering and construction in the US (and almost nowhere else) so-called 'imperial' units are still used.
• In engineering and construction (but not physics), pound-force is a unit of force, pound-mass is a unit of mass.
• You can read your equation 32 units of force = 1 unit of mass x 32 units of acceleration, but reading it as 32 units of mass = 1 unit of mass x 32 units of acceleration is simply wrong.

 

[weirdoguy]

The one that relates them in the same equation: F = m • a

weight (force) = weight (mass) • acceleration (gravity)

Can you provide a reference to physics textbook which calls mass "weight"?

 

[Digcoal]

Yes I deny that weight is not used inconsistently. Eliminating two out of the three negagives to reduce confusion: I agree that weight is used inconsistently. I think that we can all agree on that. Where there is a disagreement is that you assert that weight is used inconsistently in science; I assert that it is not: in science weight is always a force, however one example of inconsistent use is between science and commerce where weight is often used to describe a measure of mass.Answering questions directly is a good way of avoiding confusion: now I can see where you are confused.

• In science we do not use pounds and feet any more, we use SI units.
• In engineering and construction in the US (and almost nowhere else) so-called 'imperial' units are still used.
• In engineering and construction (but not physics), pound-force is a unit of force, pound-mass is a unit of mass.
• You can read your equation 32 units of force = 1 unit of mass x 32 units of acceleration, but reading it as 32 units of mass = 1 unit of mass x 32 units of acceleration is simply wrong.

“Your confusion”

I understand everything you said as you let the point circle nonchalantly over your head.

I suppose you’re going to tell me that “The Order of Operations” is a mathematical concept as well.

 

[pbuk]

I understand everything you said

So do you agree that

32 pounds-force = 1 pound-mass • 32ft/s^2

is not an example of

weight (force) = weight (mass) • acceleration (gravity)

?

Can you provide another candidate which you believe to be an example?

I suppose you’re going to tell me that “The Order of Operations” is a mathematical concept as well.

No, I am trying to reduce confusion by narrowing down the scope of this thread: widening the scope is likely to have the opposite effect.

 

[vanhees71]

This just seems ferociously silly. If you are a purist you can always substitute the phrase "This can weighs the same as that 1kg mass" for the phrase "this can weighs a kilogram". Problem solved.
I think I will not lose sleep over this.

It would be easier to say that we have clear definitions of physical quantities when doing science and engineering and we have everyday language. The latter is inadequate to communicate science and do practical work as engineers. Thus you should clearly distinguish mass and weight (as well as mass and energy, but that's another more relativistic topic of its own) when doing science and engineering. You cannot fight the sloppy use of words in everyday language, but there it's not a problem, because everybody understands what's meant and the accuracy of expressing mass in terms of its weight on Earth is (almost always) sufficient.

 

[etotheipi]

In chemistry and materials science it's common to refer to atomic weights, or composition by weight, or whatever, when strictly it should be mass. Even in physics people say "we hung a 1 kg weight on the end of the spring, and blah blah blah...".

So long as the equations are right, it really doesn't matter what you call things. Normally it's pretty obvious what someone means by the context, no?

 

[Digcoal]

So do you agree that

is not an example of

?

Can you provide another candidate which you believe to be an example?No, I am trying to reduce confusion by narrowing down the scope of this thread: widening the scope is likely to have the opposite effect.

“Pound” is weight measurement used to denote force when the “-force” modifier is added to it and mass when the “-mass” modifier is added to it.

It is exactly an example of using weight as a force and a mass within the same equation. This has created a situation that requires -force/-mass to be used as a modifier on an imprecise term used for two completely different values.

You are free to defend such a clunky use of language, but that doesn’t detract from the fact that it is clunky.

Mathematics is the complete opposite of “narrowing down the scope.” Mathematics is all about abstracting to pure ideas for easy manipulation of data and reapplication to particular instances.

Perhaps you don’t understand the point of abstraction and instantiation which drives you to defend such an illogical use of language?

The point isn’t about what established conventions are. The point is the illogic of those established conventions. The point about “Order of Operations” is that many non-mathematicians believe it is a mathematical concept which drives them to argue about a “concept” when it is actually a convention. The point is you are arguing about physical concepts when the issue is a linguistic issue.

 

[Digcoal]

Can you provide a reference to physics textbook which calls mass "weight"?

Perhaps you should query everybody who is defending the use of “weight” to mean mass.

I have been arguing this whole time to drop that silly convention because it results in threads like this.

 

[Digcoal]

...you assert that weight is used inconsistently in science...

That is not at all what I am asserting.

I have, and still do, asserted that “weight” is used inconsistently which leads to these threads. The fact that everybody keeps making straw men up about what I am asserting is further proof why language should strive for parity.

Instead of just coining better words, people want to hold on to old terms that require constant modification which creates extra levels of unnecessary cognition.

It is what it is, but it is also illogical.

 

[vanhees71]

A Mass is a mass and a force is a force. That's it. I also don't understand, why this is an issue worth of 142 postings either.

 

[pbuk]

you assert that weight is used inconsistently in science

That is not at all what I am asserting.

So what field of study were you referring to here:

Weigh and weight and weightless are all used differently within the same field of study.

And why did you not answer this question directly, but instead with a reference to an equation used in science?

What field of study are you talking about?

The one that relates them in the same equation: F = m • a

weight (force) = weight (mass) • acceleration (gravity)

Do you realize that you are not communicating clearly?

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

After thread banning @Digcoal this thread is reopened in case the OP @LT72884 has any follow-up questions. OP hasn't posted since page 1 of the thread, but that may be because of the non-helpful direction Digcoal took the thread.

 

[hutchphd]

The pound used in the USA is officially defined as 0.453 592 37 kg. As such, it is a unit of mass.

Yes, I agree. The mistaken belief that the pound is a unit of force comes directly from the engineering community

I would like to see some citations for this. In particular the definition of pound as a unit of mass.
My reading of the history is that the Mendenhall Order of 1893 simply codified the conventions of an earlier congressional act of 1866. Said earlier act listed in a table the equivalence of a kg and a liter of densest water and 2.2046 avoirdupois pounds as a standardization. Where does the official definition as mass come from...I can't find it.

 

[Dale]

I would like to see some citations for this. In particular the definition of pound as a unit of mass.
My reading of the history is that the Mendenhall Order of 1893 simply codified the conventions of an earlier congressional act of 1866. Said earlier act listed in a table the equivalence of a kg and a liter of densest water and 2.2046 avoirdupois pounds as a standardization. Where does the official definition as mass come from...I can't find it.

See the last paragraph of section 1 here: https://www.nist.gov/system/files/documents/calibrations/95-1-90.pdf

This has been the official definition of the pound since 1959. This Wikipedia article covers the history: https://en.m.wikipedia.org/wiki/International_yard_and_pound and here is the official announcement from 1959 https://www.nist.gov/system/files/documents/2017/05/09/frn-59-5442-1959.pdf

 

[hutchphd]

See the last paragraph of section 1 here:

Thanks @Dale I knew you would point me right.
I do note that the language in https://www.nist.gov/system/files/documents/calibrations/95-1-90.pdf
carefully qualifies this definition as the "U S Customary System of units for legal metrology" in addition to the SI units. This is significant because
a "legal metrology device" refers to a weighing or measuring device that is used to determine a quantity on which a charge is based for goods or service.

I think that allows us to not worry about it at all for scientific purposes and to never write that equivalence using a mathematical symbol (i.e. the equal sign). Very interesting..

.

 

[Dale]

I think that allows us to not worry about it at all for scientific purposes

I agree with you there. The only point is that if you do decide to think about it in a scientific context then you should realize that the unqualified lb is a synonym for lbm not for lbf. But there certainly is no scientific need to use lb at all.