PlayStationX

If this ridiculous pantomime of false innocence and indignant replies continues I guarantee you will start accruing infraction points left, right, and centre. Familiarise yourself with the SFN rules immediately.

 

i have no idea what are you referring to and i do not know what are you trying to say, it sounds like some kind of threat? what's SFN?

 

what rules am i breaking, being smarter than you?

 

 

As with many combinations of words it has one possible sensible interpretation only to people who already know what it is supposed to mean.

 

and your arguments are?

 

now, if you mean to claim such unnecessary thing, feel free. but without an example, argument or explanation i do not see any reason to believe you.

 

if you have really thought about it, then to come to your conclusion you would actually need to come up with an example, but since you did not post it here, it can only mean two things:

 

1.) you did not really think about it

2.) you have thought about it, but were unable to find any example

 

which one?

 

 

You have already been warned about the condescending attitude several times. Infraction on its way.

 

that is your subjective opinion not supported with any arguments.

 

 

you came here falsely accusing me of what, attitude?

 

sorry if my attitude hurts you, and if you feel like playing gestapo, then why not ban me and burn some books while you at it. otherwise, you may leave the rest of us to talk, that's what public forums are for.

 

 

...and please, don't hate me just because i'm cool

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baby,

 

you quoted this:

-"all three words are very intended, what do you mean?"

 

but you said nothing about it, you just went on to insult me ...and you say im trolling?

 

you want a real discussion and all you have are insults?

you want a real discussion and you avoid talking about the subject?

you want a real discussion and you have no idea about equation for gravity?

 

 

i wonder if anyone will realize the naked truth i said here, why would anyone get angry about it? i suppose, ignorance is bliss...

 

 

so no one has anything else to say but insults?

By "come in pairs," all that is meant is that no force can be exerted on anything without an equal and opposite force exerted on something else, i.e. what everybody (including Isaac Newton) has been saying.

 

i understand what is "meant" by it, but i hope that you too can understand what it actually means and what is the real cause of it.

 

 

This is a fact. Outright denial of this fact is not faulty logic, per se, it's just a false statement. That's why it's difficult to argue with you.

 

it is not a fact, it is very bad wording and vague phrase.

 

chickens COME out of an egg, forces DO NOT come out of anywhere. they are SINGLE property of every single charged particle - therefore, force "COME" in singles as a single property of every single charge.

 

it is funny that you want to accept such a fundamental statement about electromagnetic fields based on some half-baked, quasi law from 1687. if you really want to know how forces "COME TO BE", then better try some theory that actually deals with these forces.

 

 

please understand, Newtons laws are redundant. you can sum it all up with this: F = m*a = k* Q1*Q2/r^2

 

that is mathematical truth that describes all three laws... try it, try to ask any question three laws are supposed to answer and i will too answer that by only using above formula.

 

do you accept the challenge?

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Is it possible for you to exert a force on an object without it exerting a force on you?

 

If yes, give an example. If no, then you must at least provisionally agree that forces come in pairs.

 

yes, i think so - magnetic fields do not seem to bow to 3rd law.

 

im not saying the law is wrong, per se - im saying that by explaining it like that people will never realize what is the real CAUSE for it and WHY is it so.

 

 

i agree with your first sentence, it is a statement of causality, nothing wrong with it. however, to say "force *COME* in pairs" is a statement about the origin of the electromagnetic and gravity fields. it is so very much unnecessary statement in some law of motion from 1687.

 

 

 

F=ke*Q1*Q2/r^2 describes the force on Q1 and Q2. You cannot have a force on Q1 without having the force on Q2.

 

"force on"?

 

im not talking about force on or under, force is within and around Q1, with or without Q2.

 

the correct statement is: - "forces came in pairs when two object interact", which sounds ridiculous because it uncovers banality of the statement.

 

you could also say: - "forces come in triplets when three objects collide"

you could also say: - "forces come in n-lets when n objects collide"

 

you can not say: -"forces come in pairs", because it is not true for every case, but only the case when two objects interact, and even there we can have linear and angular momentum.

 

 

i feel silly now explaining this again,

is it not everything obvious from here: F = m*a = k* Q1*Q2/r^2 ??

 

 

 

One charge does not exert or feel a force of there are no other charges around.

 

you speak now about EXERTING force,

but before you said "forces COME in pairs", and my argument is about that.

 

it does not "feel" a force but it nevertheless posses its own force. the force for that particular charge DID NOT COME in PAIR, did it?

 

forces DO NOT COME in PAIRS, they do not even interact in pairs(only), they interact in whatever given number is there.

Arguing semantics is all you are doing here. You are arguing about the meaning of words and the best way to word Newton's laws of motion. You are not backing up your arguments with mathematics or with logic. In short, semantics.

 

yes i do, but i meant to say there is no one to argue with, as in - i have arguments, while others do not.

 

im not backing up? what? logic?

 

"only force accelerates"

 

...there is nothing to back up here, if you understood Newton's first law than you should be able to see that statement equals to what Newton said about inertia. if not, then please tell me what information is missing from my formulation of it?

 

 

please, what particular statement of mine would you like an arguments for?

F=m*a is Newton's second law, not Newton's third law...

 

The Coulomb force, F=ke*Q1*Q2/r2 is a good example of Newton's third law.

 

i do not see a need for your comment, but im glad we agree.

 

 

Forces do come in pairs. Moreover, they come in equal-but-opposite pairs. Understand this and you will understand Newton's third law.

 

oh mercy! i can not understand it if you can not explain it.

 

i've given you my explanation, why you are wrong, but instead to comment on that you keep repeating your false logic. what is the point of saying anything without providing reason and arguments for it?

 

1.) show my logic is false

2.) show your logic is true

 

forces do not "come" in pairs, that means nothing. i thought you understood this from above equation. do you not see that only two forces in that equation have to do with two charges? take one charge, then you will notice forces do not come in pairs, but they come with a number of objects in your equation, in this case two. is there any other force there?

 

 

When I get back to work tomorrow at NASA..

 

i wish you were joking. btw, i know of some bugs NASA, and the rest of the world, have in simulation software.

 

 

There is no mention of inverse square laws. Good thing, that: You're wrong. Hooke's law is not an inverse square law and it too obeys Newton's third law.

 

Hooke's law.. uh, huh. interaction within it is still the same interaction between charged particles, but i thought you agreed on inverse square law?

 

did you not say this:

-"The Coulomb force, F=ke*Q1*Q2/r2 is a good example of Newton's third law"

 

 

anyway, what statement of mine do you say is wrong?

 

i find it funny everyone is telling me "wrong", but no one cares to actually QUOTE what are they referring to. please quote, it will avoid misinterpretation.

 

 

 

You would better serve yourself if you drop the attitude. It is impeding your ability to learn. The forces you encounter in the everyday world do come in equal but opposite pairs.

 

nonsense.

 

matter interact via electromagnetic fields, so there is no other forces you could possibly be talking about here. explain, how does electromagnetic force "COME" in pair?

 

of course, you will fail to explain this, since it is high-school knowledge that electromagnetic field is a property of every single charged particle. forces we are talking about do not "come" by themselves, even less in pairs - they come with charged particles. every charge has it own SINGLE electric and magnetic force. forces DO NOT come in pairs.

 

force pairs are consequence of two objects interacting - take one charge out of Coulomb equation and tell me where is you force pair then?

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Sayonara³,

 

It certainly is, and yet you keep asking for examples to demonstrate things which have already been demonstrated by example.

 

Your MO is hardly subtle, is it?

 

that is not true, please quote it.

 

 

 

Read what people are telling you. If you don't think it addresses your points, then explain why..

 

sure, to address something you need to quote it, then provide arguments for the opinion.

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Inertia can be equated to the body's inertial mass. It's not a force. It's the mass.

 

wake up, do you not see a word "force" i that definition?

 

LOOK -----> F(inertia)= m*a

 

F= force

m= mass

 

no further comment on this, you can call it whatever you like

 

 

The employee could have said that there are 1000 grams in a kilogram as part of that video. It would be true, and yet not be an explanation of the 3rd law.

 

sure, the true explanation is the one i provided.

 

The third law is decidedly NOT only a consequence of the inverse-square law. You can observe it in e.g. a spring between two masses that are held together and then released (a simple explosion). That force is linear in x. (Edit: I see D H mentions the example of Hooke's law as well)

 

finally we have normal conversation again, with quotes and arguments.

 

the third law *IS* a consequence of the "inverse-square law". (referring to Coulomb's law and law of gravity)

 

 

it simply can not be anyhow else, because the only way material world interacts is fundamentally a result of interaction between these force fields. all the equations for such interaction follow the law of INVERSE SQUARE.

 

im talking about fundamentals, free your mind and look at the full picture.

Having just read through this and other threads, PlaystationX is clearly trolling.

 

i like your arguments and inability to understand.

 

try to define word "troll", and you may notice that it is not me, but the face you see in a mirror.

You've already been given an adequate example of why that phrase can be misinterpreted. So insist away; you'll just be repeatedly wrong.

 

so, you do agree it contains the full information from the original law and the only problem, you say, is that someone can confuse words "only", "force" and "acceleration" for something else?

 

im sorry for those people, i did not know anyone that stupid can exist, but now i agree with you. still, three words can never be misinterpreted as much as current popular definition, which this thread demonstrates very well.

 

 

 

In this thread and a couple of others, you are "answering questions" to real life physicists. Arguing semantics is not the best way to discuss terms which are given their meanings by universal convention.

 

i have no idea what are you referring to, im not arguing semantics, there is no one here to argue with, i do not see any arguments but mine.

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Is ego bosonic?

 

you're changing subject and avoiding to respond to the questions at hand, i'll take that as your confirmation. but, if you feel like talking about physics again, i welcome you.

Several people already have, including a couple of real live physicists. But again: forces act in equal and opposite pairs.

 

what are you doing?

 

i already responded to all you have said, you keep repeating your confusion as if you did not even read what was said. it is insulting to make people repeat themselves.

 

 

*And once again, thrust and drag are not an example of a force pair. I'll repeat myself:

 

are you talking to me?

sorry, i do not know what to tell you, i never said anything like that. please quote what are you referring to.

 

 

Originally Posted by me, yesterday, in case you missed it

 

The thrust pushes the air backwards with a certain amount of force, thereby pushing the plane forwards with an equal force. That is thrust. As the plane moves through the air, it has to push the air in front of it out of the way. The air then pushes back on it with an equal force. That is drag. There are four forces in total, in two opposite and equal pairs. One force from each pair is acting on the plane itself.

 

sheesh, i see now... you are arguing with NASA?

 

cant help you there, but i agree with you, they seem confused about it as well.

 

 

 

no one even responded to any of these, even less proved it wrong:

 

A.) this is where "equal and opposite force" came from and what 3rd law is all about: F= G*m1*m2/r^2

 

B.) once you state 2nd law: F= m*a, the 1st law comes out as a consequence of it: no force -> no acceleration -> no change in velocity/direction. 3rd law, as i said, is not a good law, because it is only a consequence of "inverse square law" (point A).

 

C.) 1st, 2nd & 3rd law combined: only force accelerates and unless opposed by an equal force, it always does so. F= m*a

 

 

now, please be specific and argument your insults, what do you say is wrong?

Just because you wanted all three words to appear in the phrase, doesn't mean that it can only possibly be interpreted in one way.

 

"only force accelerates",

- these three words are meant to completely replace Newton's 1st law. in that context, id like to insist this can not be misinterpreted, while it lacks none of the original information and even has some new.

 

 

 

Well, seeing as Swanson is an actual physicist doing actual physics which would blow up half of the East coast if he was so fundamentally wrong about simple principles, I don't think that's a difficult call.

 

are you saying you are picking whom to believe based on destructive power?

 

 

- Don't be to proud of this technological terror you've constructed.

The ability to destroy a planet is insignificant next to the power of the Force.

 

 

 

If you stopped being so obtuse this discussion might actually get somewhere.

 

im not in hurry, nor i planned to go anywhere. just being kind and clearing up confusion, answering questions... so, if you have anything you would like to know about Life, Universe and Everything, feel free to ask!

Inertia is not a force. If I exert a net force on an object it will accelerate. If the object has a large mass, the acceleration will be small.

 

by saying that, do you think you've explained the reason why you refuse to call it a force? where is that "equal and opposing" force in your example? inertia?

 

- "The vis insita, or innate force of matter is a power of resisting, by which every body, as much as in it lies, endeavors to preserve in its present state, whether it be of rest, or of moving uniformly forward in a straight line."

 

 

Newton 1st law is all about inertia, that's how its called - "law of inertia"

 

- "..favor the mathematically useful definition of inertia as the measure of a body's resistance to changes in momentum or simply a body's inertial mass. Mass, m, denoted something like amount of substance or quantity of matter. And at the same time mass was the quantitative measure of inertia of a body.

 

But mass as related to 'inertia' of a body can be defined also by the formula: F = m*a

"

 

where 'F' stand for FORCE

 

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

 

 

 

 

If it's a statement about the 3rd law, yes. Sisyphus has already explained why it is wrong. The statement itself is true, but the quote didn't say it was explaining the third law. You did. I'd like to confirm who is misinterpreting the third law.

 

are you having me on?

 

i gave you link then, here is again:

http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion

 

scroll down to the part about 3rd law and you will see a video there: "Explanation of Newton's third law by NASA employee.", quote is right there on the screenshot.

 

 

 

i dont mean to argue NASA's point, i have my beautiful points:

 

A.) this is where "equal and opposite force" came from and what 3rd law is all about: F= G*m1*m2/r^2

 

B.) once you state 2nd law: F= m*a, the 1st law comes out as a consequence of it: no force -> no acceleration -> no change in velocity/direction. 3rd law, as i said, is not a good law, because it is only a consequence of "inverse square law" (point A).

 

C.) 1st, 2nd & 3rd law combined: only force accelerates and unless opposed by an equal force, it always does so. F= m*a

 

 

so, if i'm confused, if i'm the one who did not understand the laws of motion and if i am the one who is misinterpreting, then please....

 

 

show me!

How do you measure how much misinterpretation is going on?

 

by reading these two threads and the rest of the internet. i measure an increased amount of misinterpretation.

 

 

Given some of your statements (e.g. the misrepresentation of the third law here and in another thread), I submit that you are not the best arbiter of such an assessment.

 

i see you say stuff,

but i do not see any reasoning, explanation or arguments for it.

 

 

shall we discuss it or shall we believe you?

"Only force accelerates" can imply an unintended meaning.

 

all three words are very intended, what do you mean?

 

 

the "force" was conceived as abstract concept.

we can see material world and how particle move and how they interact, but we were never able to see what moves them. later on we figured, it ultimately all boils down to some electromagnetic fields. that didn't solve the problem as these fields still seemed to be immaterial, spiritual, incorporeal. and so, we still can not "see" them and we still don't know what are they made of.

 

nevertheless, we wanted to talk about it and so we gave it a name - "force", as in "making something to do something", "influencing", "acting upon"... "Only force accelerates", the truth about that only "force" can do it comes out of the very definition and necessity for the word, which then makes it unnecessary to mention. still, i like it because it seems as "bold statement", while its actually a matter of semantics.

 

 

i share your interest about the history of science.

"Yes, the rock pushes back on you with as much force as you push on it. ",

- only if you are talking about some other rock that does not move when you push it. if it moves, then you obviously pushed it stronger: F(you)=m*a - F(stone)=m*a; if there was any movement, you can see from the formula that resisting force had to be less than applied force for it to happen.

 

this is all wrong, i tried to contra-argue in the way NASA explains 3rd law, but i failed. NASA's explanation doesn't seem right either, they never mention EQUALITY of the forces, rather opposite...

 

Explanation of Newton's third law by NASA employee:

-"...if thrust is greater than the drag, plane will accelerate."

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But I'm curious what the "r" signifies in F= m*a = G*m1*m2/r^2.

 

ay caramba!

 

r, is the distance between two objects (masses), in that case. if you work with charges like protons and electrons, then it is a distance between charges.

 

Newton's law of universal gravitation

http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation

 

Coulomb's law

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

 

 

from this we can take a note of similarity of macrocosmos with microcosmos and that charge and mass are two fundamental concepts of what we call material world.

 

 

From what I can understand, what you're saying is that back in the day, someone had began making these calculations using only two equal and opposite variables, when in fact they could have used any number of equal and opposite variables, not just two. Correct?

 

no, i think Newton was actually working on formulas to describe planetary motion when he came up with his 3 laws of motion. i did not say any of the formulas are wrong, just that interpretation is confusing and that all three laws actually talk about one and the same thing, so they could be much better formulated.

 

for example,

once you state 2nd law: F= m*a, the 1st law comes out as a consequence of it: no force -> no acceleration -> no change in velocity/direction. 3rd law, as i said, is not a good law, because it is only a consequence of "inverse square law".

--- Newton's laws of motion ----

 

Sure. Given a system of N particles, the force...

 

F(b,a) = -F(a,b)

 

uh, huh... i see collision, but how well it describes motion?

 

 

Forces that obey Newton's third law (e.g. most classical forces) always come in pairs. One way to look at Newton's third law is that forces represent interactions between pairs of objects that conserve momentum.

 

ok, ill explain everything now...

 

 

Q1: what are we talking about?

A1: forces and motion

 

Q2: what forces?

A2: field forces, like gravity and magneto-electric fields

 

Q3: do we have any equations of motion for them?

A3: yes. say, force between two charges: F= m*a = k*Q1*Q2/r^2

 

Q4: holy smoke! that's Newton's 3rd law!?

A4: yes, force is equal and opposite

 

Q5: ...and what about magnetic force?

A5: @$#%... shut up!

 

Q6: hey, don't yell at me, i thought we are the same person?!

 

 

forces do not come in pairs, number TWO is simply because we are dealing with two objects and each of these objects has its own magneto-electric field forces, hence they come in pair just because that's how situation is initialized. force pairs are not a fact of "natural occurrence", but the consequence of that Newton is talking about TWO objects.

 

 

 

with all that said,

let me now say that some forces DO COME in PAIRS... magneto-electric, and Yin-Yang.

 

 

 

to summarize:

- this is what 3rd law is all about: F= m*a = G*m1*m2/r^2

 

"To every action there is an equal and opposite reaction.", is misleading interpretation of that equation. it should not be stated as law, since it is only a consequence of 'real' law of interaction - 'inverse square law of attraction/repulsion'.

PlayStationX, you are saying Newton's Third Law is wrong, and in doing so you are the one embarrassing yourself.

 

no, you're failing to understand, sorry. im saying your interpretation is wrong.

 

can you give me some equation that illustrates 3rd law?

 

 

Suppose you push on a rock with some force. The rock will push back on you with a force that is equal in magnitude but opposite in direction to the force you exert on the rock. Whether or not the rock moves is irrelevant.

 

i actually agree, but the way it is understood is wrong. the way you illustrate it does not reveal what is this all about. when we come to that equation which illustrate this law i hope to be more clear about it.

 

 

 

You have a very basic and very common misunderstanding of Newton's Third Law. Third law force pairs always pertain to a pair of objects. Forces always come in pairs.

 

you have very simplistic way of thinking, sometimes referred to as blindness.

 

force ALWAYS comes in pairs?

what in the world? can you document that statement?

 

 

this is just ridiculous,

- the reason we have two forces here is because the problem is set up that way, sheesh!! it is about INTERACTION of TWO objects. if it was about interaction of three objects, then perhaps you would say forces ALWAYS come in triplets?

 

do you know at all what is it we are talking about here? give me equation that illustrates that law?

 

 

Now you are sounding very much like a crackpot.

 

don't hate me just because i'm cool

It can go wrong. A person might think the force itself is the only thing able to accelerate.

 

what else can accelerate?

 

 

Simplified one more notch: Force causes acceleration.

As you can see, however, it doesn't explain that velocity maintains its state.

 

hey, i like the way you think.

 

i want to say: -"only force accelerates",

because i think this additional information stands as true, is there any equation that has acceleration, but not 'force' in it?

 

 

i think it maintains velocity is constant (without introduction of forces to system),

since for velocity to change there need to be some acceleration. in other words it means: "without applied force velocity will not change, because ---> only force causes acceleration.", only force can change velocity and/or direction.

 

 

curvature of space-time can too perhaps, but that is another theory and is still some "force", thought represented geometrically.

The correct thing to say is not, "I think Newton's Third Law is wrong." You should say, "I do not understand Newton's Third Law." The law itself is not up for debate.

 

correct thing for you is to not embarrass yourself. im sorry that you were unable to understand, i do not debate laws, but wording and meaning. to avoid misinterpreting me please quote what are you referring to.

 

 

Yes, the rock pushes back on you with as much force as you push on it. Your confusion is in mixing up what the forces are acting on. You are acting on the rock, and the rock is acting on you. Each of you individually therefore has an unbalanced force acting on you, since the equal and opposite forces are acting on different objects.

 

your sentence does not make any sense, id say you are confused.

 

"Yes, the rock pushes back on you with as much force as you push on it. ",

- only if you are talking about some other rock that does not move when you push it. if it moves, then you obviously pushed it stronger: F(you)=m*a - F(stone)=m*a; if there was any movement, you can see from the formula that resisting force had to be less than applied force for it to happen.

 

3rd law forgets to mention one important thing - it works only for the system in equilibrium, the one without any acceleration. forces do not act in pairs, that is very silly and literal understanding, which comes as no surprise since it was formulated like that.

 

 

but i can explain it all to you, are you ready to learn?

 

 

 

Thrust and drag are not the equal and opposite forces.

 

what are you blabbering about? who said that? i have no idea what are arguing about.

 

 

this is my statement:

- only force accelerates and unless opposed by equal force, it always does so. F= m*a

 

 

if you want to show my confusion, then please argument it based on my statement. can you show that it does not work? can you show that it does not contain full information of all three laws?

 

what say you?

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Explanation of Newton's third law by NASA employee:

-"...if thrust is greater than the drag, plane will accelerate."

 

That quote is not found in that link. Where does it come from? I don't trust ellipses.

 

are you saying you disagree with it?

 

 

Case 1 is about action/reaction force pairs, and this does not deal with unbalanced forces causing an item to move.

 

Case 2: If the object is free to move, then any force at all will cause an acceleration, proportional to the mass. The limiting case is zero acceleration for zero force, ergo, there is no such thing as a resisting force. You appear to be assuming that friction is a natural circumstance rather than an external force which must be accounted for separately.

 

 

of course there is such thing as "resisting force".

 

-"Inertia is the resistance of an object to a change in its state of motion."

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

 

 

anyway, im not sure what are you talking about. i thought you have objection to my rephrasing the laws?

 

 

all im saying this can substitute all three law, it has the same meaning and applicability, but i suppose not everyone can see it...

 

- only force accelerates and unless opposed by equal force, it always does so. F= m*a

 

 

sure, i may be wrong, but then please point it out, where is the false logic? is there something that does not equal to truth?

Is there a quantifiable way to show that one statement is better than another?

 

of course there is, the statement that leaves less room for misinterpretation is better. also, according to Occam - simplest solution is the best. the fact that you simply can not go wrong with this one, makes it perfect: -"only force accelerates."

 

 

but i combined all three laws in one:

- only force accelerates and unless opposed by equal force, it always does so. F= m*a

 

 

 

Klaynos,

 

This is just a reminder as I can see it wandering in that direction.

 

im not sure if that was towards me, can you point out what you mean?

 

in any case, im just trying to discuss semantics, definitions and their meaning. i do not propose new definition, im just explaining what it really means, its pure logic and semantics, usage, meaning and interpretation of the words, thats what this thread is about, i gather.

 

i insist that my definition does NOT lose applicability nor any information of original, but only makes it more clear.

"Resisting force" is always equal and opposite in direction. You push a rock, it pushes you back with the same force, and you both move.

 

But in that sense, they act on different objects. The motion of an object is the result of forces acting ON it, as has already been discussed.

 

i do not think rock pushes you back equally, in fact the difference in how much you push it and it pushes you will be the net force deciding initial acceleration. it is not "active" force, its not real force, it is "passive". it does not act, it does not push - it resists.

 

the definition of "resistance/inertia" in its meaning almost implies "opposite direction", and it most certainly implies passivity. in this sense, i think it can be understood as both "acting" on same object, while only one is actually 'acting'.

 

 

anyway,

 

-"To every action there is always opposed an equal reaction.", is false. the correct statement is more like:

 

if you cant push it, then it resists your applied force - obviously with the same amount of resistance(force), but NEVER MORE. however, if you managed to push it, then you just won over "resisting force" - it was unable to balance your force and it got accelerated in the direction you applied the force.

 

 

 

Explanation of Newton's third law by NASA employee:

-"...if thrust is greater than the drag, plane will accelerate."

 

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

 

actually, NASA does not seem to get it either, what they talk about is hardly -"To every action there is always opposed an equal reaction." - they do talk about OPPOSITE direction, but they never say it is ALWAYS equal. in fact, for acceleration to happen there has to be UNBALANCE, which is 1st law. what im trying to say is that 1st and 3rd law really talk about the same thing, but from slightly different perspective.

 

 

 

to sum it all up, 1st, 2nd and 3rd law should be put in one, like this:

- only force accelerates and unless opposed by equal and opposite force, it always does so. F= m*a

 

 

this practically means that if you see something has changed its velocity or direction, there is some force acting there. but that doesn't mean there ain't some forces if it is not moving or accelerating, it just means forces are at balance when we observe uniform motion.

Actually my objection is to your shortening of the statement.

 

ok, i want to claim that "only force accelerates", contains all the information of the original statement, plus some more information, which makes it better definition. i want to claim that this short statement can substitute the original statement, completely and in every case.

 

 

 

And there is no circular motion at constant velocity, by definition — velocity is a vector.

 

i agree definition is such, i was referring that to lead these two statements in contradiction:

 

1.) when light bends due to gravity, it does not accelerate - it follows curvature of space-time

 

2.) magnetic field can not accelerate charged particles, but still it can change their direction

 

 

 

"uniform motion" is defined, and not ambiguous

 

i agree. it is explained, that if you read original text you may notice that he means constant velocity as well as constant acceleration. but when making new, modern formulation why not make it crystal clear. why not call "change in motion" - acceleration, we have a name for it, why not use it? why make it confusing? whats the point of words "tend", "external", "unbalanced"?

 

the sentence does not have "focus", its hard to see what is it about and why is it important. it kind of tries to be about "frames of reference" while it can not be about anything else but the force, since the "force" is a 'primary' word needing description.

 

 

In regard to the OP, I suspect the word "tend" may have some ties to the notion that Newton displaced, which was that an object's natural tendency was to come to rest, i.e. that was a dynamic thing. Moving objects tend to come to rest. The translation of Newton is saying that no, it's only objects already at rest that tend to remain that way, and they do not start to move on their own, i.e. there is no tendency for spontaneous motion: motion from a state of rest requires a force.

 

word "tend" has no place in there, it gives no explanation for anything , it only makes statement more undefined. it makes you feel as if there is some threshold to which object resist to change motion.

 

it is as if some more inert objects will not react at all, it makes you think that some minimal force will produce no effect what so ever, or that is a matter of chance.

 

definition should use words like: all, none, never, always, only...

 

 

...Galileo realized that force acting on a body determines acceleration, not velocity. This insight leads to Newton's First Law—no force means no acceleration, and hence the body will maintain its velocity.

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

 

this sums up my line of thought

What is the "resisting force" before the applied force is applied? Why doesn't the object move in response to this?

 

The only "resisting force" I can think of is friction, and we can discuss forces without worrying about friction. There is no inherent "resisting force," and it is not the reaction force of Newton's 3rd law, so this is not a good answer to the OP.

 

at first i meant to be humorous because it seemed this silly "explanation" kind of worked, but i did not really think it makes any sense, i was just blabbering... however, after thinking about it, well now, i think it makes perfect sense!

 

"resisting force" is like inertia, only better! ...since it also works with 3rd law, 2-in-1.

 

 

it can also be a friction and drag... or maybe not, not sure, if they fit description count them in

Isn't circular motion at constant speed "uniform" ?

 

i agree that question is valid. it goes on to show how original formulation is vague.

 

 

this is the essence of it cut with Occam's razor:

- only force accelerates

 

 

still, circular motion with constant velocity leaves a question - is there really some acceleration in there, or is it just a curvature in space-time?

there is an old Chinese saying that goes like this:

- "if you can't fix it with rubber, it's not worth fixing."

 

simply put rubber everywhere and dress up as Bat-man.

newton's 1st law states that acceleration can only be acheived if an external UNBALANCED force acts upon an object

 

newton's 3rd law states that forces ALWAYS occur in pairs

 

so how can there ever be an UNBALANCED FORCE?

 

let me disagree with everyone, passionately!

 

 

OP seem to be closest to answering own question, which is actually a good question and all the answers here were not so good, until now...

 

 

this is simply about "resistance", that's it. so, it means this:

 

- if "resisting force" is less than applied force object will accelerate (unbalanced), otherwise "resisting force" will be equal in magnitude and opposite in direction.

"Uniform motion is perpetual unless acted upon by a force"

 

i agree with that.

 

 

but lets analyze it,

what is that sentence about, some motion and force?

 

 

well, i believe it is about 'CHANGE in MOTION' aka ACCELERATION.

 

 

 

so what can you possibly say about acceleration and force?

 

1.) force can cause acceleration (force accelerates)

2.) force always causes acceleration (force always accelerates)

3.) only force can cause acceleration (only force accelerates)

 

i think its #3, thought it sounds more trivial and even questionable

"object at rest stays at rest and that an object in uniform motion stays in uniform motion unless acted upon by..."

 

you are right. its badly worded, too many words.

 

it should go like this:

-an object in uniform motion stays in uniform motion unless acted upon by force

 

 

1.) not "external force", any force

 

2.) mentioning object at rest is not important, it is still "uniform motion", only with zero velocity

 

 

 

maybe better yet, it should go like this:

- only force can accelerate objects

 

 

...may the force accelerate you!