# comparison of weight and voltage

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The following post explaining my comparison of weight and voltage as expressions of potential energy has been contested as being "gibberish:"

electric charge 'pushes' against an insulator with the amount of voltage it is poised to transmit at the moment the circuit closes. Thus I think it is reasonable to compare weight to voltage, where an obstacle preventing an object from falling impairs gravitational motion in the same way an insulator prevents an electric charge from flowing further within the circuit. In both cases, force is met with resistance and the "equal and opposite reaction" of the resistance is the potential of the impeded kinetic energy (flow). If this reasoning is incorrect, I of course want to hear why, but I see nothing faulty about it, honestly.

What is gibberish? The idea that "electric charge 'pushes' against an insulator?" What else would it be doing while waiting for sufficient voltage to build up to the point of being able to spark across a gap in the circuit or some other insulator separating the conductors?

Is it gibberish to say that "an obstacle preventing an object from falling impairs gravitational motion in the same way an insulator prevents an electric charge from flowing further within the circuit?" If a bowling ball dropped out of a helicopter is stopped by a bridge on the way to the ground, is the bridge not impeding the flow of the ball to the ground?

Is it gibberish to say that "in both cases, force is met with resistance and the "equal and opposite reaction" of the resistance is the potential of the impeded kinetic energy (flow)?" Ok, this one is a bit harder to read but it applies a Newtonian principle, that actions have equal and opposite reactions. That means that a moving object resisted by a medium or barrier pushes against the barrier with force, which is returned in an equal and opposite force from the medium/barrier to the object. That force resisting the kinetic flow is the potential energy the flow has to continue in the absence of the resistance, no?

Maybe I could have worded it differently, but this is all physics, is it not?

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This is actually on topic with your other topic; and the answer is still the same. I am not sure I understand why you INSIST on staying ignorant of the textbook physics. You are more than welcome to criticize it but that would be much more effective after you know what it actually says.

There's not a lot more we can say on this, lemur, no matter how many threads you post on it. You insist on reducing things to your own way of thinking without knowing what the physics says, and then you blame everyone else for having no idea what it is you're trying to say.

I promise you: unless you do so while driving or, potentially, while crossing the street, reading will likely NOT kill you. Try it.

~mooey

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Lemur , ask mooeypoo a one line technical question .

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Maybe I could have worded it differently, but this is all physics, is it not?

No, it is not. It is gibberish. Incoherent babbling.

Newton "stood on the shoulders of giants". Einstein built on the mathematics of Riemann. No one has ever understood physics without reading the work of those that came before them. Newton was not smart enough. Einstein was not smart enough. You aren't either.

Edited by DrRocket
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Lemur , ask mooeypoo a one line technical question .

Hal, I already answered it. Lemur seems to want to be 100% correct despite of physics rather than take what he can get and go study a bit more. Here. A repost:

The same sphere would not push down as hard (i.e. with as much force) if it had less gravitational potential, e.g. on the moon. I think I can safely say that weight is to gravitational potential what charge-voltage is to electrostatic potential. I have to be careful saying this, though, because someone might accuse me of being physics-illiterate and spreading false knowledge.

A good start of avoiding this is to pose things you're uncertain about as a question rather than a statement.

Weight is a force (Gravitational force) and Voltage is an electric potential difference, so in that aspect I'd just be careful in the similar-framing. But in general, I guess you can think of it similarly in terms of conceptual imagining of the effects;

• To get gravitational potential we can use the equation $W=\int F \cdot dr$ (which leads to mgh on earth)
• To get electric potential we can use the equation $V=\int E \cdot dl$

In that aspect, they're similar.

Just worth noting also that electric potential will only act on objects with an electric charge while gravitational potential will act on all mass.

~mooey

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What then is Electro Motive Force ?

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electric charge 'pushes' against an insulator with the amount of voltage it is poised to transmit at the moment the circuit closes.

This makes no sense because electric charge does not exert a force on the insulator.

Also, voltage isn't really "transmitted." Charge is transmitted, along with energy. Voltage is a measure of the potential difference between two arbitrary locations, and the total energy transmitted is a function of both charge and voltage (how much charge and how much potential it has).

In both cases, force is met with resistance and the "equal and opposite reaction" of the resistance is the potential of the impeded kinetic energy (flow).

No, the potential energy has nothing to do with any force. Force and energy are two entirely different things. Potential energy exists even if the object is not obstructed while falling.

If this reasoning is incorrect, I of course want to hear why, but I see nothing faulty about it, honestly.

You would be better received on this forum if, admitting your lack of basic physics training, you recognized your ideas are very likely wrong and sought improvements, rather than assuming they are correct and fighting whenever they are rejected.

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This is actually on topic with your other topic; and the answer is still the same. I am not sure I understand why you INSIST on staying ignorant of the textbook physics. You are more than welcome to criticize it but that would be much more effective after you know what it actually says.

There's not a lot more we can say on this, lemur, no matter how many threads you post on it. You insist on reducing things to your own way of thinking without knowing what the physics says, and then you blame everyone else for having no idea what it is you're trying to say.

I promise you: unless you do so while driving or, potentially, while crossing the street, reading will likely NOT kill you. Try it.

~mooey

I've actually been reading a lot about potential energy since this discussion started. I'm not insisting on reducing things to my way of thinking. I just use my method to explain something in a way that someone who doesn't seem to understand might get some insight. I've said it many times I'm not competing with any textbooks or any other books. The only reason I'm being defensive is because I don't think I said anything incorrect. The only thing I'm questioning about what I said is if a current stopped by opening a circuit in fact exerts force or "pushes" against the insulator blocking it from re-closing the circuit. I believe it would since electricity flowing through a conductor is analogized as electron force-pressure, thus there must be force within the insulated conductor "equal and opposite" to the force of the insulator impeding the current from flowing.

I don't mind people telling me that my analogy wasn't helpful to them better understanding what I was talking about. What bothers me is when experts in physics completely undermine the validity of what I said by calling it "gibberish." This confuses me as to what part of what I said was wrong and what part was not. Obviously I was not wrong that a falling object 'at rest' is pushing down on the surface it is 'resting' on with the force of gravity. And it is also quite self-evident that the force with which it is pushing expresses a potential to be in motion if the surface resisting its motion was not present. So why would physicists be saying that these statements are indefensible in terms of physics?

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Hal, I already answered it. Lemur seems to want to be 100% correct despite of physics rather than take what he can get and go study a bit more. Here. A repost:

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The similarity is more imagined than real. You can integrate any vector field over a line. The (classical Newtonian) gravitational field is conservative. The electric field is only conservative in the non-time-varying case. Unless the field is conservative the value of the line integral depends on the whole path and not just the end points. When a vector field is non-conservative it is not derivable as the gradient of a scalar field (aka potential function). In the time varying case "voltage" is not well-defined.

lemur is in desperate need of some time with a physics book. There is no effective substitute.

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This makes no sense because electric charge does not exert a force on the insulator.

What do surplus free electrons in copper do when they encounter air? They must attempt to dissipate into the air. If they have enough voltage, they do and cause a spark and their kinetic energy gets converted into a chemical reaction producing ozone or electrolyzing water vapor or something like that.

No, the potential energy has nothing to do with any force. Force and energy are two entirely different things. Potential energy exists even if the object is not obstructed while falling.

How is the potential energy (capacity to do work) not directly evident in the force/weight of the falling object? Even if the object is in free fall, its acceleration is the product of gravitational force. Gravitational force does work (force over a distance), which keeps it accelerating, right? Now I'm getting confused because it seems as if kinetic energy gets stored as potential as an object goes up before falling back down. I guess it wouldn't matter in terms of potential meaning the capacity to do work, though, since the force is being expressed over a distance regardless of the speed or resistance to the object falling. This actually explains why both a falling object and an object sitting on the ground can both have potential energy, i.e. because they both have the capacity to do further work. No?

You would be better received on this forum if, admitting your lack of basic physics training, you recognized your ideas are very likely wrong and sought improvements, rather than assuming they are correct and fighting whenever they are rejected.

It's foolish to allow arrogance to blind you to the possibility of being wrong, but it's just as foolish and egoistic to falsely claim to think you're wrong when you don't really think you are just to appear humble/submissive. I wish none of this was about who was credentialed and who isn't. Good discussion puts all that aside and sticks to critical discussion of content. I have no problem admitting when I'm wrong, but it confuses me when people tell me things I'm saying are wrong when they're not.

Edited by lemur
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Also:

What else would it be doing while waiting for sufficient voltage to build up to the point of being able to spark across a gap in the circuit or some other insulator separating the conductors?

Voltage will not "build up" as more electrons arrive at the insulator. If I have a DC power supply set to a fixed voltage, it will supply electrons with a specific potential energy, and they will all arrive at the insulator that way. Charge may build, but that is not the same as voltage.

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The similarity is more imagined than real. You can integrate any vector field over a line. The (classical Newtonian) gravitational field is conservative. The electric field is only conservative in the non-time-varying case. Unless the field is conservative the value of the line integral depends on the whole path and not just the end points. When a vector field is non-conservative it is not derivable as the gradient of a scalar field (aka potential function). In the time varying case "voltage" is not well-defined.

lemur is in desperate need of some time with a physics book. There is no effective substitute.

What empirical references does this post contain? Conduction-band electrons in a conductor transmit waves of pressure. When they reach an insulator, they attempt to transmit their energy through the medium. This could cause the shielding of a wire to melt, air to spark, etc. A heavy enough truck parked on a weak enough bridge will also cause the bridge to collapse to allow the truck to continue expressing its potential as kinetic motion of falling.

Also:

Voltage will not "build up" as more electrons arrive at the insulator. If I have a DC power supply set to a fixed voltage, it will supply electrons with a specific potential energy, and they will all arrive at the insulator that way. Charge may build, but that is not the same as voltage.

What word describes the strength of charge intensity besides voltage then? My understanding is that the behavior of electricity in conductor is analogous to gas-pressure. The voltage in the circuit is whatever amount of force it is being pushed with. It doesn't build up because the circuit is opened. Is that what you're saying?

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Is electro motive force measured in volts ?

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What do surplus free electrons in copper do when they encounter air? They must attempt to dissipate into the air. If they have enough voltage, they do and cause a spark and their kinetic energy gets converted into a chemical reaction producing ozone or electrolyzing water vapor or something like that.

This has nothing to do with applying a force on the insulator.

How is the potential energy (capacity to do work) not directly evident in the force/weight of the falling object? Even if the object is in free fall, its acceleration is the product of gravitational force. Gravitational force does work (force over a distance), which keeps it accelerating, right?

Suppose I measure an object to have a mass of 1kg. I put it on the ground. It has no gravitational potential energy. I pick it up and put it on a tall shelf. It has some small amount of gravitational potential energy.

Solely with knowledge of its mass, I know nothing about its gravitational potential, which depends on its height.

The fact that you can use mass and height to determine gravitational potential similarly does not mean that "the 'equal and opposite reaction' of the resistance is the potential of the impeded kinetic energy", because it is not the resisting force that "is the potential." The resisting force has nothing to do with the potential; it is a separate entity, and even without any resisting force the potential still exists.

Now I'm getting confused because it seems as if kinetic energy gets stored as potential as an object goes up before falling back down.

Yes, it does.

I guess it wouldn't matter in terms of potential meaning the capacity to do work, though, since the force is being expressed over a distance regardless of the speed or resistance to the object falling. This actually explains why both a falling object and an object sitting on the ground can both have potential energy, i.e. because they both have the capacity to do further work. No?

Sure. An object sitting on the ground can fall into a cave. An object which is connected to a rope and pulley and consequently falls extremely slowly has the same potential energy as one which is dropped freely from the same height.

It's foolish to allow arrogance to blind you to the possibility of being wrong, but it's just as foolish and egoistic to falsely claim to think you're wrong when you don't really think you are just to appear humble/submissive.

I am not asking you to believe you are wrong all the time. However, your present attitude is very frustrating for anyone who discusses physics with you. Generally, you contrive an explanation which makes very little sense and includes several falsehoods, determine you "see nothing faulty about it," and then argue strenuously when anyone points out the flaws.

I don't believe it is arrogance which blinds you to the possibility of being wrong. I believe it is arrogant and frustrating to continue advancing your beliefs as credible when you know admittedly very little formally about the subject at hand.

Perhaps a wise neutral approach would be to post your ideas with the comment, "Does this make sense?", rather than the comment "This makes perfect sense to me," and then to accept criticism graciously, as a contribution which helps you learn and advance your ideas.

I wish none of this was about who was credentialed and who isn't. Good discussion puts all that aside and sticks to critical discussion of content. I have no problem admitting when I'm wrong, but it confuses me when people tell me things I'm saying are wrong when they're not.

The credentialed folks have a certain advantage in the critical discussion of your content.

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Newton "stood on the shoulders of giants". Einstein built on the mathematics of Riemann. No one has ever understood physics without reading the work of those that came before them. Newton was not smart enough. Einstein was not smart enough. You aren't either.

For the record, I would not claim to be above reading any physics book. I read them often, in fact, along with other sources and I read posts on this forum with great interest as well. My weak point is mathematical language like "scalar fields," which I sometimes google to try to understand but often I find what was expressed in terms of expensive mathematical language could have been expressed in simpler empirical terms once I do understand. No matter, I do try to learn more by reading posts with unfamiliar language and decoding it slowly and painfully sometimes. Other times, I remind myself that I am not getting paid for what I am doing so I am free to concentrate on what interests me the most. When I am wrong, I will not claim to be right. However, I will not blindly accept anyone's claim that I am wrong without reasonable grounds. It's as important to rigorously evaluate the legitimacy of critique as it is to evaluate the legitimacy of any other argumentation.

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What empirical references does this post contain? Conduction-band electrons in a conductor transmit waves of pressure.

"Pressure" is a poor term for this, because pressure indicates a physical force over an area, which is not the case.

When they reach an insulator, they attempt to transmit their energy through the medium. This could cause the shielding of a wire to melt, air to spark, etc. A heavy enough truck parked on a weak enough bridge will also cause the bridge to collapse to allow the truck to continue expressing its potential as kinetic motion of falling.

This is again a poor analogy. The electrons do not push on the insulator until it fails, allowing sparking. Rather, the electric field they generate becomes strong enough to exert an electric force on its constituent atoms that rips electrons off of them, allowing a current to flow. In an alternating current, the electrons in the wire do not even leave -- they merely cause the electrons in the insulator to oscillate as well.

It's not like water flowing through a pipe and hitting a blockage with physical force.

What word describes the strength of charge intensity besides voltage then?

What is "the strength of charge intensity"? What does that mean? "Charge intensity" is a meaningless term in physics, as far as I know. You will need to explain what exactly you want to know.

My understanding is that the behavior of electricity in conductor is analogous to gas-pressure. The voltage in the circuit is whatever amount of force it is being pushed with. It doesn't build up because the circuit is opened. Is that what you're saying?

No, it is not.

If I push more electrons towards the insulator, but the electrons still have the same energy, the voltage across the insulator will stay exactly the same, even as I push millions of electrons at it.

If I give the electrons on average more energy per electron, the voltage across the insulator will increase.

Voltage is the measure of the potential difference between any two points, and so if my battery supplies three volts, the voltage across the insulator will be three volts no matter how long I leave the battery connected to push electrons at it.

Voltage is not a measure of electric potential energy, but electric potential only.

Is electro motive force measured in volts ?

http://en.wikipedia.org/wiki/Electromotive_force

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What empirical references does this post contain? Conduction-band electrons in a conductor transmit waves of pressure. When they reach an insulator, they attempt to transmit their energy through the medium. This could cause the shielding of a wire to melt, air to spark, etc. A heavy enough truck parked on a weak enough bridge will also cause the bridge to collapse to allow the truck to continue expressing its potential as kinetic motion of falling.

Oh fer crissake. Try ANY book with a nane like "Advanced Calculus" for the rudiments of line integtrals. Kaplan's book would do. Calculus on Manifolds by Mike Spivak is one of the best with a more modern flavor.

For thetheory of classical electrodynamics, Classical Electrodynamics by J.D, Jackson is the standard. Equally good is Electrodynamics of Continuous Media by Landau and Lifshitz. Somewhat easier books are Introduction to Electrodynamics by Griffiths and Classical Electromagnetic Radiation by Marion. The Feynman Lectures on Physics covers electrodynamics at an introductory level, and many other topics as well.

This is stuff that is so well-known and standard that references ought not be necessary.

If you are tryiong to confirm that you have no idea what you are talking about, then you are doing a bang-up job.

What word describes the strength of charge intensity besides voltage then? My understanding is that the behavior of electricity in conductor is analogous to gas-pressure. The voltage in the circuit is whatever amount of force it is being pushed with. It doesn't build up because the circuit is opened. Is that what you're saying?

There is no such thing as "charge intensity". There is a magnitude to the electric field and there is "charge density". Voltage is not force, is is somewhat analogous to a pressure difference, but voltage is strictly speaking only a valid concept in the static case in which the e-field is conservative.

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This has nothing to do with applying a force on the insulator.

Why not then?

Suppose I measure an object to have a mass of 1kg. I put it on the ground. It has no gravitational potential energy. I pick it up and put it on a tall shelf. It has some small amount of gravitational potential energy.

Gravity is the force with which the object pushes down. As long as it is pushing down, it has the potential to move in that direction whether it is actually moving or not. So its potential energy can only be measured within a frame of motion that you apply BUT its actual potential to move is present in the force it is exerting, which is empirically observable/measurable as weight. Energy is the capacity to do work, right? Isn't force a capacity to do work as long as it is consistent over the distance of work to be done?

The fact that you can use mass and height to determine gravitational potential similarly does not mean that "the 'equal and opposite reaction' of the resistance is the potential of the impeded kinetic energy", because it is not the resisting force that "is the potential." The resisting force has nothing to do with the potential; it is a separate entity, and even without any resisting force the potential still exists.

I see your point about the existence of potential without resisting force, but the resisting force DOES indicate that there is a potential to do work present, doesn't it? Otherwise it wouldn't be resisting anything.

I am not asking you to believe you are wrong all the time. However, your present attitude is very frustrating for anyone who discusses physics with you. Generally, you contrive an explanation which makes very little sense and includes several falsehoods, determine you "see nothing faulty about it," and then argue strenuously when anyone points out the flaws.

I'm just being honest. When a criticism cites what is faulty about something I say, then I can understand the grounds and agree. Without any direct criticism with reasoning/grounds, what basis do I have for accepting or rejecting the argument?

I don't believe it is arrogance which blinds you to the possibility of being wrong. I believe it is arrogant and frustrating to continue advancing your beliefs as credible when you know admittedly very little formally about the subject at hand.

You could fail every arithmetic test you ever took but if you said that 2 + 2 = 4, you'd be right and it wouldn't be arrogant to say so. High test scores don't make arithmetic right, logic does.

Perhaps a wise neutral approach would be to post your ideas with the comment, "Does this make sense?", rather than the comment "This makes perfect sense to me," and then to accept criticism graciously, as a contribution which helps you learn and advance your ideas.

That is usually what I do. When people criticize me uncritically be calling my language "gibberish" or telling me that I don't understand physics, though, what other means do I have of keeping the criticism content-focussed except to reassert what I said that I believe(d) to be correct? You can't second-guess your understanding just because someone else tells you you're stupid. You need a reason that deals with the content - not ad hom attacks.

The credentialed folks have a certain advantage in the critical discussion of your content.

Credentials don't prove substantive arguments. They're just an indication that someone has been exposed to training that should have made them capable of forming rigorous substantive argumentation. They're no guarantee that someone is going to be right at any given moment.

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Dr.Rocket , this is a question , I don't claim to be advanced to any level I am seeing being discussed . You say voltage is not force . Why then is electro motive force measured in volts .

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Dr.Rocket , this is a question , I don't claim to be advanced to any level I am seeing being discussed . You say voltage is not force . Why then is electro motive force measured in volts .

Being measured in the same units does not make two things the same.

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There is no such thing as "charge intensity". There is a magnitude to the electric field and there is "charge density". Voltage is not force, is is somewhat analogous to a pressure difference, but voltage is strictly speaking only a valid concept in the static case in which the e-field is conservative.

Thank you for your book suggestions. I don't think they have those at the public library I use but I'll keep my eyes open for similar titles. "Intensity" may not be your term of preference but it is English and commonly understood. I am more concerned with the content of what is said than the style of saying it. Writing style aesthetics is not physics, btw. "Magnitude" is a term I'm familiar with but I don't know what it refers to empirically. It sounds abstract. "Charge density" sounds less abstract but what does it refer to exactly? In a conductor, there are conduction band electrons that change levels practically continuously, correct? So it sounds like "charge density" would refer to the amount of conduction-band electrons in an excited state relative to some total sample. It is clear that you use textbook terminology and style that I'm not familiar with, but that really doesn't prove that everything you ever say is going to be right and that anything I say is necessarily wrong. For some reason, you seem to want me to be socially deferential on the basis of credential-status but I'm just interested in substantive arguments, whatever their style. I will try to understand yours even if you don't feel the need to bother with mine. I still don't think it's fair for you to keep denigrating me, though, just because I don't want to make your level of abstraction a condition for me to think about and discuss physical mechanics.

Dr.Rocket , this is a question , I don't claim to be advanced to any level I am seeing being discussed . You say voltage is not force . Why then is electro motive force measured in volts .

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You need a reason that deals with the content - not ad hom attacks.

Apparently you do not understand the nature of an ad hominem argument.

Ad hominem argument : "You are stupid, therefore your argument is fallacious."

Unnecessary insult: "Your argument is silly, and shows that you are stupid."

Valid, helpful observation:"Your argument contains several misconceptions and mis-statements of fact that demonstrate that you are ignorant of the subject matter. Please read a physics book."

Edited by DrRocket
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Can force be measured in volts ? I hope this doesn't sound like the same question .

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Why not then?

Because the fact that wires spark does not prove there is a physical force on the insulator.

Gravity is the force with which the object pushes down. As long as it is pushing down, it has the potential to move in that direction whether it is actually moving or not. So its potential energy can only be measured within a frame of motion that you apply BUT its actual potential to move is present in the force it is exerting, which is empirically observable/measurable as weight.

The fact that something has gravitational potential is indeed evident if it has weight. However, its weight is not the same thing as its potential, and the amount of weight does not necessarily correlate to the amount of potential energy, given that height also matters.

Energy is the capacity to do work, right?

In one sense, yes.

Isn't force a capacity to do work as long as it is consistent over the distance of work to be done?

No, it is not a "capacity" to do so in the way energy is. Energy is used up while doing work -- once something does work, it has less energy. However, objects do not "have" force or use it up while doing work. As such, force is not a capacity to do work.

I see your point about the existence of potential without resisting force, but the resisting force DOES indicate that there is a potential to do work present, doesn't it? Otherwise it wouldn't be resisting anything.

Yes.

I'm just being honest. When a criticism cites what is faulty about something I say, then I can understand the grounds and agree. Without any direct criticism with reasoning/grounds, what basis do I have for accepting or rejecting the argument?

"But it makes sense to me!" could perhaps be replaced with "So explain in more detail why point 3 is inaccurate, as I don't get the bit about walruses."

You could fail every arithmetic test you ever took but if you said that 2 + 2 = 4, you'd be right and it wouldn't be arrogant to say so. High test scores don't make arithmetic right, logic does.

Also knowing what all the terms mean. That seems to be a key issue.

That is usually what I do. When people criticize me uncritically be calling my language "gibberish" or telling me that I don't understand physics, though, what other means do I have of keeping the criticism content-focussed except to reassert what I said that I believe(d) to be correct?

"Could you explain why? What definition is more accurate for 'penguinal force'?"

From our position, saying "that's wrong -- here's a link" and getting back "but it makes sense to me!" is exceedingly frustrating. Of course it makes sense to you -- you posted it in the first place, and clearly you're a poor judge of what makes sense in physics!

You can't second-guess your understanding just because someone else tells you you're stupid. You need a reason that deals with the content - not ad hom attacks.

Generally these have not been ad homs but "that just makes no sense", which is not a fallacy but merely a statement.

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Apparently you do not understand the nature of an ad hominem argument.

Ad hominem argument : "You are stupid, therefore your argument is fallacious."

Unnecessary insult: "Your argument is silly, and shows that you are stupid."

Valid, helpful observation:"Your argument contains several misconceptions and mis-statements of fact that demonstrate that you are ignorant of the subject matter. Please read a physics book."

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