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The Concept Of Mass


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#18 Moronium

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Posted 11 April 2019 - 11:06 AM

"The amount of matter that an object contains is its mass."

 

Incidentally, this does not equate matter to mass, they are two separate concepts.

 

I agree that energy and mass (another word for matter, in your definition) are two different concepts, if that's what you're getting at.  I have discussed these differences at some length already.  Ralf just noted it also.

But the formula E = M equates them.  The c2 element can be left out without changing the equality.  It's just a quantitative factor, not qualitative.  
Again, this is what generates some (but not all) of the source of my confusion, I guess.

Edited by Moronium, 11 April 2019 - 11:15 AM.


#19 Moronium

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Posted 11 April 2019 - 11:21 AM

That is what I tried to give you. There is no perfect definition. I gave you the one which works well for me.

 

I guess I'm still not making myself too clear.  I said I was NOT looking for a definition.



#20 ralfcis

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Posted 11 April 2019 - 01:09 PM

You know what works for me? Clouds are made of cotton candy. Rain makes cotton candy shrink and that's why clouds' mass shrinks when it rains. 



#21 Moronium

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Posted 11 April 2019 - 08:12 PM

By manipulating the F = MA formulation you find that mass boils down to "resistance to acceleration."  But that is a circular notion with no independent meaning. It seems like a fictitious bookkeeping notion that is invented just to make things "balance."  You need force and acceleration to give it any kind of meaning, but even then....I'll come back to this.

 

 

I don't remember the thread, but I'm pretty sure that is was Dubbo who mistakenly argued that if an object was accelerated, it would just keep accelerating.  Why wouldn't it?  This is a legitimate question.

 

Aristotle assumed the opposite with his "impetus" theory of force.  An object would not continue accelerating, and certainly would not continue moving once set in motion, he said, because the force (impetus) applied was finite and would therefore dissipate with time. If you apply x amount of force, then that would  carry the object only x distance.  On the face of it, this view also appears to "make sense."

 

It was Galileo who first "answered" these questions (later refined by Newton). In both cases "inertia" (aka "mass") is being overlooked.  An object will not keep accelerating indefinitely because there is a built in "resistance" to acceleration which will eventually overpower the initial force applied unless it keeps being applied.  But it won't "stop" all it's own either, as Aristotle thought.  According to Newton, it also takes a "force" to stop a moving object just as it takes one to give it increased speed.  Even it the initial force is finite, it will not dissipate with time.

 

So this amounts to a sort of "compromise."  The effect of being accelerated will last "forever" if no further force is applied, but, as Aristotle concluded, that "effect" will necessarily be finite and limited. Viewed in this light, inertia might be viewed as a "force" (or counter-force) of its own.  It keeps a moving object moving while also resisting, and eventually "overcoming," any external force applied to it.  So is inertia (i.e. mass) a "force," after all?

 

One question that has never been satisfactorily answered (at least insofar as general acceptance is concerned) is how and why inertia exists in the first place.  Where does this mysterious "force" come from?  What is it's origin?  What "causes" it?  Nobody seems to know.


Edited by Moronium, 11 April 2019 - 08:39 PM.


#22 Moronium

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Posted 11 April 2019 - 09:21 PM

 Viewed in this light, inertia might be viewed as a "force" (or counter-force) of its own.  It keeps a moving object moving while also resisting, and eventually "overcoming," any external force applied to it.  So is inertia (i.e. mass) a "force," after all?

 

 

It might be worth noting that so-called "fictitious forces" (aka "inertial forces") arise when objects are accelerated in Newtonian mechanics.

 

Why are these forces deemed to be "fictitious?"  Because, the argument goes, they arise without one object "pushing on" another, hence they cannot be real forces. There is no direct mechanical interaction involved. They arise from "outside the system."  But does that really make inertial forces "fictitious?"  They seem to be real, and quite predictable.


Edited by Moronium, 11 April 2019 - 09:40 PM.


#23 ralfcis

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Posted 11 April 2019 - 09:53 PM

I took a course in university about modelling mechanical objects like electrical circuits. Inductance had the same properties as a spring and capacitance had the same properties as inertia or mass. Inertia is therefore not a force, it is mass. Voltage is the force that induces movement of current through components. A capacitor allows AC current to pass through but blocks DC current once the capacitor is charged. This is equivalent to a heavy block put on top of your hand and then trying to crush your hand by hitting the block with a sledge hammer. Because the current is an AC spike, the heavy mass does not move, and your hand does not feel the sledge hammer blow. The inertia or mass of the block has saved your hand from being crushed. Sorry, I can't think right now, bedtime.



#24 GAHD

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Posted 11 April 2019 - 10:15 PM

 

 

I agree that energy and mass (another word for matter, in your definition) are two different concepts, if that's what you're getting at.  I have discussed these differences at some length already.  Ralf just noted it also.

But the formula E = M equates them.  The c2 element can be left out without changing the equality.  It's just a quantitative factor, not qualitative.  
Again, this is what generates some (but not all) of the source of my confusion, I guess.

 

Your problem is that you're not using the full equation, you're using the laymans dumbed down versions. It's more like (Energy)^2 = (Mass*C^2)^2 + Momentum*C^2

Mass without momentum is E=MC^2
Momentum without mass is E=PC
 



#25 Moronium

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Posted 11 April 2019 - 10:18 PM

Your problem is that you're not using the full equation, you're using the laymans dumbed down versions. It's more like (Energy)^2 = (Mass*C^2)^2 + Momentum*C^2

Mass without momentum is E=MC^2

 

It's mass that we're talking about here.  The formula you give for that is the same one I used, and which has been published endlessly in scientific journals and texts.  Were they using a "dumbed-down" version of the formulation too, ya figure?


Edited by Moronium, 11 April 2019 - 10:50 PM.


#26 Moronium

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Posted 11 April 2019 - 10:29 PM

Your problem is that you're not using the full equation. It's more like (Energy)^2 = (Mass*C^2)^2 + Momentum*C^2

 

As I have already noted in prior posts, the concept of "relativistic mass" seems to have lost favor with modern physicists.  Your (re) formulation of the original equation seems to rest on this debatable concept.

 

As I also noted, I don't pretend to be any kind of expert on the topic, but, as I understand it, "relativistic mass" equals "rest mass" when viewed from the "center of momentum" frame of reference., a particular, and, if you will, preferred, frame of reference for this phenomenon.  The problem with "relativistic" views, as I see it, is one I have already pointed out, to wit:

 

The attempt to eliminate a preferred frame can do nothing other than create confusion and conceptual chaos while generating irresolvable inconsistencies and contradictions. (Post #11)

 


Edited by Moronium, 11 April 2019 - 10:39 PM.


#27 Moronium

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Posted 11 April 2019 - 11:03 PM

I took a course in university about modelling mechanical objects like electrical circuits. Inductance had the same properties as a spring and capacitance had the same properties as inertia or mass.  Inertia is therefore not a force, it is mass.

 

....Because the current is an AC spike, the heavy mass does not move, and your hand does not feel the sledge hammer blow. The inertia or mass of the block has saved your hand from being crushed.

 

I don't see how your premise leads to your conclusion here, Ralf.

 

Let's say I'm tied to some railroad tracks with a train going 80 mph coming straight at me and which is now just a few feet from me.

 

But then a miracle happens.  Another force, let's call it superman, suddenly intercedes and stops the train.

 

I emerge unscathed.  Does that prove that "superman" is not a force?

 

One force can oppose, and offset, another.  Does that mean that one not a force any more?

 

The moon has lateral motion which (the force of) inertia maintains, for example.  Because of this it is able to offset the "force" of the earth's gravity.  Rather than being sucked down to earth, it just eternally orbits it because the opposing forces have reached an equilibrium.


Edited by Moronium, 11 April 2019 - 11:36 PM.


#28 ralfcis

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Posted 12 April 2019 - 12:47 AM

A capacitor is not a force, the power supply supplies the force, the capacitor absorbs the force, the capacitor is a physical thing, not an anti-force. Why not read up on it yourself since you're the one who supposedly wants to know things so long as they agree with what you already know. Here's a nice little paper on it but oh gosh darn there's math involved. Way over your head. Maybe you can find something simpler for you to absorb.

 

https://www.academia...hanical_Systems



#29 GAHD

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Posted 12 April 2019 - 01:05 AM

As I have already noted in prior posts, the concept of "relativistic mass" seems to have lost favor with modern physicists.  Your (re) formulation of the original equation seems to rest on this debatable concept.

 

As I also noted, I don't pretend to be any kind of expert on the topic, but, as I understand it, "relativistic mass" equals "rest mass" when viewed from the "center of momentum" frame of reference., a particular, and, if you will, preferred, frame of reference for this phenomenon.  The problem with "relativistic" views, as I see it, is one I have already pointed out, to wit:

And yet, it is. Particle accelerators directly show relativistic mass, that's one of the reasons CERN had to be so big. A smaller torus would have needed a LOT more power once it got up to speed, simply because of angles and that very real full equation. So I'm not really following you with the unsubstantiated loss of favor prattle. Where is that kinda tripe coming from? Energy to momentum transfer is stagnated by the logarithmic returns involved at the high end due to the mass gain...it's measured.



#30 exchemist

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Posted 12 April 2019 - 03:43 AM

And yet, it is. Particle accelerators directly show relativistic mass, that's one of the reasons CERN had to be so big. A smaller torus would have needed a LOT more power once it got up to speed, simply because of angles and that very real full equation. So I'm not really following you with the unsubstantiated loss of favor prattle. Where is that kinda tripe coming from? Energy to momentum transfer is stagnated by the logarithmic returns involved at the high end due to the mass gain...it's measured.

I think what Moronium may be referring to is the preference among physicists nowadays to mean rest mass when they speak of mass, and to use other ways to reflect the increase in effective mass arising from relative motion. I have certainly been told more than once, old fogey that I am, that "relativistic mass" is not a concept in widespread use nowadays. That doesn't mean it is an invalid concept, just that the consensus seems to be it can be confusing and so "mass" is taken by default to mean rest mass. 



#31 OceanBreeze

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Posted 12 April 2019 - 04:46 AM

I think what Moronium may be referring to is the preference among physicists nowadays to mean rest mass when they speak of mass, and to use other ways to reflect the increase in effective mass arising from relative motion. I have certainly been told more than once, old fogey that I am, that "relativistic mass" is not a concept in widespread use nowadays. That doesn't mean it is an invalid concept, just that the consensus seems to be it can be confusing and so "mass" is taken by default to mean rest mass. 

 

Yes, "preference" seems to be the operational word.

 

I have also been told not to use relativistic mass as it is an outdated term (among the elites) but I still find it useful, along with things like centrifugal force and cycles per second, which are also looked upon by staring down the noses of the more erudite!

 

Even the explanations of why relativistic mass is not used, are forced to use it!

 

From Wiki:

 

"The term mass in special relativity usually refers to the rest mass of the object, which is the Newtonian mass as measured by an observer moving along with the object. The invariant mass is another name for the rest mass of single particles. The more general invariant mass (calculated with a more complicated formula) loosely corresponds to the "rest mass" of a "system".

 

Thus, invariant mass is a natural unit of mass used for systems which are being viewed from their center of momentum frame (COM frame), as when any closed system (for example a bottle of hot gas) is weighed, which requires that the measurement be taken in the center of momentum frame where the system has no net momentum.

 

Under such circumstances the invariant mass is equal to the relativistic mass (discussed below), which is the total energy of the system divided by c^2 (the speed of light squared).

 

For other frames, the relativistic mass (of a body or system of bodies) includes a contribution from the "net" kinetic energy of the body (the kinetic energy of the center of mass of the body), and is larger the faster the body moves.

 

Thus, unlike the invariant mass, the relativistic mass depends on the observer's frame of reference. However, for given single frames of reference and for isolated systems, the relativistic mass is also a conserved quantity.

 

Although some authors present relativistic mass as a fundamental concept of the theory, it has been argued that this is wrong as the fundamentals of the theory relate to space–time. There is disagreement over whether the concept is pedagogically useful.[2][3][4] The notion of mass as a property of an object from Newtonian mechanics does not bear a precise relationship to the concept in relativity.[5] Oxford lecturer John Roche states that relativistic mass is not referenced in nuclear and particle physics, and that about 60% of authors writing about special relativity do not introduce it.[1]"

 

So, if you want to be included among the 60% who are elite, you don't use it, but for the rest of us slobs it is still OK, I guess :pardon:



#32 GAHD

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Posted 12 April 2019 - 04:48 AM

I think what Moronium may be referring to is the preference among physicists nowadays to mean rest mass when they speak of mass, and to use other ways to reflect the increase in effective mass arising from relative motion. I have certainly been told more than once, old fogey that I am, that "relativistic mass" is not a concept in widespread use nowadays. That doesn't mean it is an invalid concept, just that the consensus seems to be it can be confusing and so "mass" is taken by default to mean rest mass. 

I can sort of see that, bit of low level algebra and you end up with (m^2)*(C^4)=E^2-pC^2 which gives you rest mass, but NOTHING is ever at rest in reality



#33 Moronium

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Posted 12 April 2019 - 06:19 AM

A capacitor is not a force, 

 

I never said a capacitor is a force.  I'm talking about inertia.  I'm not saying that inertia is a force either, but, for the reasons I've already stated, it can be viewed that way.  It's more a matter of semantics.

 

Conceptually, its much easier for me to understand how a "force" is tantamount to "the ability to do work" (energy) than that "resistance to acceleration" is.

 

They like to say that inertia is a "property" of matter, but what does that really say or mean?  As I noted there are phenomena that are commonly referred to as "inertial forces" as it stands.   Perhaps "force" is a property of inertia (mass).

 

As Popeye just said, quoting wiki, "The notion of mass as a property of an object from Newtonian mechanics does not bear a precise relationship to the concept in relativity."

 

We're (or at least I am) talking about the concept of mass, not momentum, not electromagnetism, not capacitors and not other "different" things.


Edited by Moronium, 12 April 2019 - 06:43 AM.


#34 ralfcis

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Posted 12 April 2019 - 06:30 AM

Right, you're a literal thinker, you can't understand through analogies or how similar forms of formulae apply across many physical applications. I assume you have no experience with electronics so my analogy of how a capacitor behaves the same way as inertia or mass is meaningless and probably quite confusing. Continue trying to not understand things and hold on to the sheer mystery of it all on your own terms.