In the angular momentum equation, L = r x p, when the magnitude of the radius changes, which one of the remaining variables is correctly conserved ?

[Mandlbaur]

I am going to go right back to the beginning and start again.

 

I shall work through your proposition a line at a time trying to knock it into proper shape so you don't end up with fallacious conclusions.

 

You are welcome to come along for the ride, you never know you may learn something to your advantage.

 

 

 

So the first line

 

"Both angular momentum and momentum are accepted to be conserved values"

 

 

 

 

Can we move on to the next line?

[studiot]

 

 

Can we move on to the next line?

 

What, no technical questions at all?

 

Well I will ask one then.

 

Under what conditions is angular momentum conserved for a particle proceeding along a straight line as shown in post#99?

 

There is enough information in post#99 to fully answer this.

 

However it is only true in 2 dimensions.

 

So a second question

 

Why is it not true then in a general 3 dimensional case?

[Mandlbaur]

 

What, no technical questions at all?

 

Well I will ask one then.

 

Under what conditions is angular momentum conserved for a particle proceeding along a straight line as shown in post#99?

 

There is enough information in post#99 to fully answer this.

 

However it is only true in 2 dimensions.

 

So a second question

 

Why is it not true then in a general 3 dimensional case?

 

 

Your questions are irrelevant because they fall outside the scope of my OP.

[studiot]

 

 

Your questions are irrelevant because they fall outside the scope of my OP.

 

Thank you for telling me that you have been wasting my time.

[Mandlbaur]

 

Your questions are irrelevant because they fall outside the scope of my OP.

Thank you for telling me that you have been wasting my time.

 

 

It is a classic symptom of confirmation bias to accuse your opponent of your own uncooperative behaviour.

[imatfaal]

!

Moderator Note

Mandlbaur

Everyone in this thread realises what is wrong with your conception and why this leads to your fallacious assertions - except you. You have been really quite rude to everyone who has tried to explain your misunderstanding. Now you are insulting a member who has spent considerable time trying to re-engage your understanding of momentum and angular momentum. Personally I will not put up with this level of ingratitude.

I am moving this thread to speculations and will close it fairly promptly if you do not start to respond to counter-arguments - for your further guidance, your replies to counters should be more than denials and slights. You are challenging a keystone of mechanics - and seem to be doing so based on a misunderstanding of a very basic equation and a general lack of knowledge of the field. The thread would have remained open for as long as it took for these problems to be remedied - but if you are going to spurn help then your OP will be treated as base speculation.

Do not respond to this moderation within the thread.

[Bender]

So since our discussion in March, it appears very little has changed. Let's summarise, so we can pick up where we left off:

 

1) You base all this on very poorly executed "experiments", most of which aren't closed systems at all and without any quantitative data.

 

2) Pulling in a spinning mass with a string makes the mass move on a spiral. This means the force is not perpendicular to the motion and linear momentum is not conserved.

 

3) All equations of angular momentum and the conservation thereof can be derived from Newton's laws of motion. Claiming that angular momentum is not conserved implies that you also claim Newton's laws of motion are incorrect.

 

4) You never considered these points (perhaps best to start with these):

Ever heard of helicopters? Don't you think the engineers designing them would have noticed if their calculations completely failed to predict the behaviour of the helicopter? What about the engineers designing satellites and space probes. They should have been in for quite a surprise when their yo-yo de-spin device completely failed to perform or they didn't manage to target their satellites with the reaction wheels they designed. Except, you know, they didn't because it all worked fine.

 

Perhaps you have heard of Kepler's laws of planetary motion? They are entirely consistent with conservation of angular momentum; in fact, the concept of conservation of angular momentum has its origin in Kepler's second law. Don't you think astronomers would, at some point in the last couple of centuries, have noticed something if they completely and utterly fail to predict planetary motion?

Edited June 16, 2017 by Bender

[Mandlbaur]

So since our discussion in March, it appears very little has changed. Let's summarise, so we can pick up where we left off:

 

1) You base all this on very poorly executed "experiments", most of which aren't closed systems at all and without any quantitative data.

 

2) Pulling in a spinning mass with a string makes the mass move on a spiral. This means the force is not perpendicular to the motion and linear momentum is not conserved.

 

3) All equations of angular momentum and the conservation thereof can be derived from Newton's laws of motion. Claiming that angular momentum is not conserved implies that you also claim Newton's laws of motion are incorrect.

 

4) You never considered these points (perhaps best to start with these):

 

 

This post is not the same as my previous posts.

 

None of your arguments presented here are valid against this OP.

 

I have presented a logical argument.

 

To dismiss this argument, it is necessary to invalidate the premisses or fault the logic.

 

Alternatively it is mandatory to accept the conclusion drawn.

 

Any other response is irrational.

[Strange]

 

 

To dismiss this argument, it is necessary to invalidate the premisses or fault the logic.

 

Alternatively it is mandatory to accept the conclusion drawn.

 

Any other response is irrational.

Nonsense.

[Roger Dynamic Motion]

This is why looking over the mathematical proofs for conservation of energy is important. Part of the proof is defining a closed system. The other part shows the torque aspects. The proof also identifies which vectors are involved.

doesn't the hub, in a closed system ,rotates with the rotation of the radius at the same time ,,because the hub is the career of the torque to acceleration.

[swansont]

doesn't the hub, in a closed system ,rotates with the rotation of the radius at the same time ,,because the hub is the career of the torque to acceleration.

 

 

It depends on the system.

[Bender]

 

 

This post is not the same as my previous posts.

 

None of your arguments presented here are valid against this OP.

 

I have presented a logical argument.

 

To dismiss this argument, it is necessary to invalidate the premisses or fault the logic.

 

Alternatively it is mandatory to accept the conclusion drawn.

 

Any other response is irrational.

Others have already done that quite adequately and patiently.

 

I suggest we start over and focus on to these two questions:

1) Are engineers making enormous errors when designing machines based on their understanding of angular momentum?

2) Do astronomers completely fail to predict the movement of planetary objects?

[Roger Dynamic Motion]

It depends on the system.

Are you saying that relative motion is not a fact in the case of (Closed system) .

[Mordred]

 

 

This post is not the same as my previous posts.

 

None of your arguments presented here are valid against this OP.

 

I have presented a logical argument.

 

To dismiss this argument, it is necessary to invalidate the premisses or fault the logic.

 

Alternatively it is mandatory to accept the conclusion drawn.

 

Any other response is irrational.

As mentioned your logic argument is ib error for the reasons already provided.

 

As you will be the only one suffering from your logic argument. As well as not listening to others with greater expertise. Like Studiot I will not waste anymore time trying to convince you.

 

You cannot teach to someone unwilling to learn. Though quite frankly a good textbook would be enough.

Are you saying that relative motion is not a fact in the case of (Closed system) .

A closed system is a very specific state.

Studiot if I recall already defined the closed system for both linear and angular momentum.

Edited June 19, 2017 by Mordred

[Mandlbaur]

Others have already done that quite adequately and patiently.

 

 

I suggest we start over and focus on to these two questions:

1) Are engineers making enormous errors when designing machines based on their understanding of angular momentum?

2) Do astronomers completely fail to predict the movement of planetary objects?

 

 

Incorrect. No-one has dismissed my argument adequately.

 

To make that unsubstantiated claim that is irrational, negligent, wishful thinking and typical of a person suffering from confirmation bias.

 

Although it is absolutely not necessary for me to respond to your out of scope questions, I will nevertheless provide responses:

 

1) Engineers do not use conservation of angular momentum when designing machines. If they did, their machines would not work properly. I have had this discussion on various occasions with engineers and none have been able to provide any evidence of anything which varies in radius that was designed using conservation of angular momentum. They use conservation of energy which predicts substantially different results.

 

2) Astronomers do fail to predict the movements in which they are using conservation of angular momentum in their calculations and the radius is variable. I have had this discussion with various astronomers and they have failed to produce any data which confirms actual measurements of planetary movement against predictions. There are also various examples of planetary motion discrepancies.

 

Now let's go back to the reality of the argument provided in the OP:

 

Logic is the cornerstone of science.

 

I have provided a logical argument.

 

To dismiss it one would have to invalidate the premisses or fault the logic.

 

There has been no argument levelled against this logic which has not been directly tackled and dismissed.

 

The only thing outstanding is for all of you to accept the conclusion drawn.

You cannot teach to someone unwilling to learn.

 

 

Absolutely agreed.

[Strange]

Incorrect. No-one has dismissed my argument adequately.

 

It is one inadequate to you. As you will never be willing to admit you are wrong, see where your errors lie, and actually learn anything then none will ever able t provide an argument that you find adequate.

 

 

I have provided a logical argument.

To dismiss it one would have to invalidate the premisses or fault the logic.

 

Initially, I thought this was just a mistake or a misunderstanding or how rational thought works. As you keep repeating it, despite multiple explanations as to why it is wrong, I can only assume you are now deliberately lying. That is rather pathetic.

 

 

 

The only thing outstanding is for all of you to accept the conclusion drawn.

 

Oh well, at least you have a sense of humour.

[swansont]

Are you saying that relative motion is not a fact in the case of (Closed system) .

 

 

No. I said that whether the hub rotates depends on the system. You can have systems where the entire thing is rotating and a system where the hub is fixed.

[studiot]

 

 

No. I said that whether the hub rotates depends on the system. You can have systems where the entire thing is rotating and a system where the hub is fixed.

 

 

Roger, think of the difference between a freewheel and a fixed hub in a bicycle.

[Mordred]

 

 

Incorrect. No-one has dismissed my argument adequately.

 

 

Now let's go back to the reality of the argument.

Perfect then identify where the linear momentum in your system is involved. As per your logic arguments.

 

Prove to us a wheel with a stationary axis has linear momentum.

 

Do so mathematically. Show us your superior knowledge. Or learn

 

(linear monemtum must have a vector or force parallel to the direction of motion)by literal definition.

 

Identify this vector. I have asked you to do this before but you ignored that challenge.

 

Support this claim from your logic argument then.

 

Premise 4: , it is the component of momentum perpendicular to the radius which must be conserved when the magnitude of the radius changes.

 

Here is the definition of linear momentum once again for you.

 

 

"Linear momentum is a vector whose direction is parallel to the velocity of the particle. with relations p=mv "

 

Identify which particles or otherwise that satisfies the above definition.

 

In other words put up or shut up. The only arguments in your defense you have thus far provided is "everyone else is wrong because you claim so" So snap to it and defend your claim above.

 

I bet you cannot defend it mathematically can you? prove us wrong and we will listen.

 

Ball is in your court.

 

(just to avoid an argument on definitions)

Here is a quick Google search on the definition itself.

https://www.google.ca/search?ie=UTF-8&client=ms-android-samsung&source=android-browser&q=linear+momentum+definition&gfe_rd=cr&ei=yBRJWZT4D8Pe8AeysY_oAQ

 

"Linear momentum is a vector quantity defined as the product of an object's mass, m, and its velocity, v. Linear momentum is denoted by the letter p and is called momentum for short: Note that a body's momentum is always in the same direction as its velocity vector"

 

 

So feel free identify the linear momemtum component in that wheel system I mentioned above.

Edited June 20, 2017 by Mordred

[studiot]

Anyone has to learn to walk before they can run.

 

I offered you the opportunity to work through the walking stage to reach your equation in considerably more detail than you will find in any single textbook or three.

 

And the only running you did was to run away from this opportunity.

 

So I will leave you with the the following thoughts.

 

Your very very elementary equation is not always true.

 

For instance it is not true in the case of point particles with mass, spinning on their own axes.

These have angular momentum, but r = zero.

 

Again it is true in the case where r refers to a plane curve.

But it is untrue in the case of a twisted three dimensional curve.

 

There are many other complicated cases to explore.

[imatfaal]

!

Moderator Note

 

Mandlbaur

 

Everyone in this thread realises what is wrong with your conception and why this leads to your fallacious assertions - except you. You have been really quite rude to everyone who has tried to explain your misunderstanding. Now you are insulting a member who has spent considerable time trying to re-engage your understanding of momentum and angular momentum. Personally I will not put up with this level of ingratitude.

 

I am moving this thread to speculations and will close it fairly promptly if you do not start to respond to counter-arguments - for your further guidance, your replies to counters should be more than denials and slights. You are challenging a keystone of mechanics - and seem to be doing so based on a misunderstanding of a very basic equation and a general lack of knowledge of the field. The thread would have remained open for as long as it took for these problems to be remedied - but if you are going to spurn help then your OP will be treated as base speculation.

 

Do not respond to this moderation within the thread.

 

 

 

!

Moderator Note

 

Mandlbaur - please reread the above quoted moderation and the rules of this forum before continuing to issue blanket refusals to engage with members argument; this vainglorous grandstanding is both insulting to the members trying to discuss the matter and hampering you from discovering your errors.

 

Do not respond to this moderation within the thread.

 

[Bender]

1) Engineers do not use conservation of angular momentum when designing machines. If they did, their machines would not work properly. I have had this discussion on various occasions with engineers and none have been able to provide any evidence of anything which varies in radius that was designed using conservation of angular momentum. They use conservation of energy which predicts substantially different results.

The specific situation of a changing radius in a closed system indeed doesn't come up very often. One example is the de-spin device on satellites, which work great.

 

However, since you are making claims that go against what has been shown to work in every quantitative experiment ever, could you at least show how you would use your hypothesis to make calculations on a concrete example.

 

2) Astronomers do fail to predict the movements in which they are using conservation of angular momentum in their calculations and the radius is variable. I have had this discussion with various astronomers and they have failed to produce any data which confirms actual measurements of planetary movement against predictions. There are also various examples of planetary motion discrepancies.

We aren't talking about "examples of planetary motion discrepancies". According to you, all planetary motions should be completely and utterly wrong.

 

Can you please demonstrate how you would calculate the orbit of a planet or moon of your choice?

Edited June 20, 2017 by Bender

[swansont]

 

2) Astronomers do fail to predict the movements in which they are using conservation of angular momentum in their calculations and the radius is variable. I have had this discussion with various astronomers and they have failed to produce any data which confirms actual measurements of planetary movement against predictions. There are also various examples of planetary motion discrepancies.

 

 

And yet the same physics has predicted the return of Halley's comet again and again.

 

You need to detail these alleged discrepancies. A blanket accusation of failure of conservation of angular momentum doesn't wash.

[Phi for All]

!

Moderator Note

Off-topic post about 3 Powers of the Defender hidden. Speculation is difficult enough for an OP without others posting their own pet concepts.

[Mandlbaur]

Anyone has to learn to walk before they can run.

 

I offered you the opportunity to work through the walking stage to reach your equation in considerably more detail than you will find in any single textbook or three.

 

And the only running you did was to run away from this opportunity.

 

So I will leave you with the the following thoughts.

 

Your very very elementary equation is not always true.

 

For instance it is not true in the case of point particles with mass, spinning on their own axes.

These have angular momentum, but r = zero.

 

 

 

 

If r = zero, angular momentum = zero.