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Old 11th August 2019, 08:14 PM   #161
Robin
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Originally Posted by Elagabalus View Post
Did Pete and Peter use a bicycle pump? Presta or Schrader?
Maybe you could find another thread. We are good for our quota of trolls here.
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Old 11th August 2019, 08:16 PM   #162
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Originally Posted by GnaGnaMan View Post
Does it really have to be someone's fault? Ok, let it be mine, if it helps.
agreed. Your fault. But it doesn't help because you are not teachable. Robin came into this guessing, but learned as the thread progressed. Now Robin has it spot on. What's your excuse for still wandering around in lala land?


Originally Posted by GnaGnaMan View Post
The relevant Bernoulli equation describes a 1-dimensional stream.



https://en.wikipedia.org/wiki/Ventur...enturiFlow.png

see if you can take that principle and explain why the air pressure in the cone is less than atmospheric?
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Old 11th August 2019, 08:22 PM   #163
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Originally Posted by Robin View Post
There is also a difference between speed and velocity in one dimension, so can you please tell me which you mean!
Go with velocity. We wouldn't want anyone time travelling.
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Old 11th August 2019, 08:27 PM   #164
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Originally Posted by Red Baron Farms View Post
agreed. Your fault. But it doesn't help because you are not teachable. Robin came into this guessing, but learned as the thread progressed. Now Robin has it spot on. What's your excuse for still wandering around in lala land?
lol


Quote:


https://en.wikipedia.org/wiki/Ventur...enturiFlow.png
https://en.wikipedia.org/wiki/Ventur...enturiFlow.png

see if you can take that principle and explain why the air pressure in the cone is less than atmospheric?
I don't think you can explain it from that.
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Old 11th August 2019, 08:34 PM   #165
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The difference between speed and velocity is literally in the first chapter of a high school physics textbook.
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Old 11th August 2019, 08:36 PM   #166
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Originally Posted by GnaGnaMan View Post
Go with velocity. We wouldn't want anyone time travelling.
Another odd comment.

Do you think that speed and velocity are the same in one dimension unless time travel is involved?

Wrong again.
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Old 11th August 2019, 08:38 PM   #167
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Originally Posted by Robin View Post
Maybe you could find another thread. We are good for our quota of trolls here.

***SIGH*** Pete and Peter did not document(very well) what they did precisely so we are left with only speculation as to the cause of straw-cone interface not producing the desired result.*




*Not to mention why PnP thought it was analogous to the vacuum of space
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Old 11th August 2019, 08:39 PM   #168
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Originally Posted by Robin View Post
Another odd comment.

Do you think that speed and velocity are the same in one dimension unless time travel is involved?

Wrong again.
No, I don't think that. Is anything on-topic coming?
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Old 11th August 2019, 08:46 PM   #169
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Originally Posted by Elagabalus View Post
***SIGH*** Pete and Peter did not document(very well) what they did precisely so we are left with only speculation as to the cause of straw-cone interface not producing the desired result.*









*Not to mention why PnP thought it was analogous to the vacuum of space
Ok, sorry for the flame.
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Old 11th August 2019, 09:08 PM   #170
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Originally Posted by GnaGnaMan View Post
No, I don't think that. Is anything on-topic coming?
You don't think that it is on topic to establish whether you mean speed or velocity?
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Old 11th August 2019, 09:17 PM   #171
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Originally Posted by Robin View Post
You don't think that it is on topic to establish whether you mean speed or velocity?
Don't mind me. I'm just being parochial. It's just that, in my experience, balloons don't just blow up on their own.
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Old 11th August 2019, 09:22 PM   #172
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Then there is this part:
Originally Posted by GnaGnaMan View Post
The pull of the rubber stores energy. This becomes pressure of the air inside the balloon. When the air can escape it does. Per Bernoulli's principle the pressure sinks as the air speeds up.
You need to clarify. Do you mean "Per Bernoulli's principle the pressure *inside the balloon" sinks as the air speeds up?".

If so then, no, that is not Bernoulli's principle. The pressure inside the balloon would continue to decrease if the velocity of air escaping decreased. That is not what the principle is about.
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Old 11th August 2019, 09:24 PM   #173
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Originally Posted by GnaGnaMan View Post
Don't mind me. I'm just being parochial. It's just that, in my experience, balloons don't just blow up on their own.
And that relates to the topic - how?
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Old 11th August 2019, 09:26 PM   #174
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Originally Posted by Red Baron Farms View Post
Robin came into this guessing, but learned as the thread progressed. Now Robin has it spot on.
Thanks for that. It seems to be the only real interest in threads like this.

Just as the only real interest in "Intelligent Design" is when I read a proper biologist explaining what is really going on and I learn something.

I can understand people who don't want to learn about physics. But I can't understand those who don't want to learn about physics but to continue talking about it anyway.
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Old 11th August 2019, 09:34 PM   #175
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Originally Posted by Robin View Post
Then there is this part:

You need to clarify. Do you mean "Per Bernoulli's principle the pressure *inside the balloon" sinks as the air speeds up?".

If so then, no, that is not Bernoulli's principle. The pressure inside the balloon would continue to decrease if the velocity of air escaping decreased. That is not what the principle is about.
The pressure inside the balloon depends on the properties of the rubber of the balloon. It's going to depend mainly on the radius of the balloon. It's not a reliable function. It's mass produced rubber.
You can google some empirical measurements of party balloons, if you're interested.
Think of Bernoulli's principle as giving the relationship between pressure and velocity at an infinitesimal slice of time dt.
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Old 11th August 2019, 09:43 PM   #176
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Originally Posted by Robin View Post
And that relates to the topic - how?
Ahh. Don't mind me. I'm drunk. When I sober up I will probably realize that the difference between speed and velocity here is not if the air streams into or out of the balloon.
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Old 11th August 2019, 11:35 PM   #177
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Originally Posted by GnaGnaMan View Post
That's nonsense on too many levels to unpack. Just apologize and we won't talk about it anymore.
Oh, now your claim is that math is nonsense. Care to support that claim or could it be that differential calculus is beyond your ken?
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Old 12th August 2019, 03:40 AM   #178
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Originally Posted by GnaGnaMan View Post
lol



I don't think you can explain it from that.
I can easily explain it from that. However, that wasn't the point. I was seeing if you could. Obviously not. So lets try one even easier made by the faculty at the University of Colorado Boulder Department of Chemical and Biological Engineering... This is literally part of their interactive teaching series, although the interactive part of YouTube is now broken. But that's ok because we can easily provide that here at ISF. There are plenty of members here that understand such basic physics.

YouTube Video This video is not hosted by the ISF. The ISF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.
I AGREE


This is as close as I could find to the problem of the car with a balloon and a cone attached. Is the pressure more at A,B,C,D or E all the same?

Originally Posted by GnaGnaMan View Post
I'm drunk.
But lets apply it to our problem more specifically and give you the opportunity to display for all that yes indeed that non-functioning drunk brain of yours really can be useful sometimes.

Far left would be our balloon. the constrictions to flow in the car itself and the cone on the right the same as the paper cone, with the farthest right atmospheric. It's not exact, but it is close enough.

This time rank them in order of pressure, highest to lowest.

ABCD?
DCBA?
ACDB?
ABDC?
CDBA?
...
and so on and so forth.

Go on. Give it a shot.
Originally Posted by GnaGnaMan View Post
Just apologize.
So Mr. unteachable woo spawner, tell us in a relative way which points have more or less pressure. Prove me wrong. I dare you to actually get the answer correct and make me eat crow. I will gladly apologize profusely.

Edit to add: What I ask in return is that if you are incapable of figuring out the correct answer, then at least stop posting your woo here. It is confusing the people actually trying to learn.
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Old 13th August 2019, 04:01 AM   #179
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Originally Posted by abaddon View Post
Oh, now your claim is that math is nonsense. Care to support that claim or could it be that differential calculus is beyond your ken?
I do not know how you could read that "claim" into what I wrote.
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Old 13th August 2019, 04:25 AM   #180
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Originally Posted by Red Baron Farms View Post
I can easily explain it from that.
You can explain it incorrectly, of course.

Quote:
But that's ok because we can easily provide that here at ISF. There are plenty of members here that understand such basic physics.
I am sure of that. The problem is that an understanding of physics is not sufficient. You also need someone who is willing to deal with the hostility of certain people here.
My pet theory is that behavior such as yours is part of a pathological learning process. Understanding things is hard. Insulting people is easy. If you take people going away as winning an argument then insulting people is easiest way to do so.
This can explain why you shut down genuine questions and have become a graveyard for BS.

Quote:
This is as close as I could find to the problem of the car with a balloon and a cone attached. Is the pressure more at A,B,C,D or E all the same?
The first thing you should notice is that A,B,C and D are all pressures inside the cone. None of these correspond to ambient pressure.

Quote:
Far left would be our balloon. the constrictions to flow in the car itself and the cone on the right the same as the paper cone, with the farthest right atmospheric. It's not exact, but it is close enough.
Why is any of those atmospheric? Under what conditions would that be the case?
I have asked this earlier but unfortunately no one was able to answer. I've looked it up on my own by now, so if anyone's interested I can supply it.

Quote:
So Mr. unteachable woo spawner, tell us in a relative way which points have more or less pressure. Prove me wrong. I dare you to actually get the answer correct and make me eat crow. I will gladly apologize profusely.
You should be apologizing because your behavior is morrally wrong; not because of some sort of bet. I hope you will work on that.

In the meantime I will take that phony, profuse apology. The question implies a very low Mach number. Because of this and that, the pressure is proportional to the diameter of the tube. A has the highest diameter.C the smallest. I think D is supposed to be slightly narrower than B. That means that A has the highest pressure, C the lowest and the others in between, in accordence to the previous sentence.

Quote:
Edit to add: What I ask in return is that if you are incapable of figuring out the correct answer, then at least stop posting your woo here. It is confusing the people actually trying to learn.
I believe that you are genuinely deluded about your behavior.
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Old 13th August 2019, 05:49 AM   #181
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Originally Posted by GnaGnaMan View Post
The question implies a very low Mach number. Because of this and that, the pressure is proportional to the diameter of the tube. A has the highest diameter.C the smallest. I think D is supposed to be slightly narrower than B. That means that A has the highest pressure, C the lowest and the others in between, in accordance to the previous sentence.
Long winded way to simply say ABDC, but it is correct. I happily apologize profusely. You actually are capable of learning when not building strawmen.

Next step: start adding more specifics. Let's add an E to the far far right and is atmospheric in our balloon car cone system. A already is the balloon and higher than atmospheric pressure according to how full we blew that balloon up.

So A is higher than atmospheric. (inside the balloon)
Is B?
Is C?
Is D?
and we know E is atmospheric pressure. (By definition since it is open air)

And just to keep this conversation going I will answer it now under spoiler tags. See if you can get this one right too:

B we don't fully know. It is somewhere between the pressure in the balloon which is higher than atmospheric and the pressure of C which is less than atmospheric. The pressure rapidly drops though, so most likely less.

C is less than atmospheric

D is greater pressure than C but less than atmospheric pressure


Hopefully now you can work out for yourself why the cone actually exerts negative thrust....simply due to the atmospheric pressure vectors. But if that still eludes you, then just ask. And as long as you ask without using strawmen that rudely misstate what I have said so far, my replies will stay polite as always. But if you try pulling that strawman crap on me again, expect the exact same hostility in the future. Have I made myself clear?
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Old 13th August 2019, 07:14 AM   #182
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Originally Posted by Robin View Post
Then there is this part:

You need to clarify. Do you mean "Per Bernoulli's principle the pressure *inside the balloon" sinks as the air speeds up?".

If so then, no, that is not Bernoulli's principle. The pressure inside the balloon would continue to decrease if the velocity of air escaping decreased. That is not what the principle is about.
No, the pressure in a partially inflated balloon is often higher than a fully inflated one because of properties of the tension in rubber and such. Think about blowing up a balloon when are you blowing hardest vs when is it easier that is a direct measurement of the pressure.
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Old 13th August 2019, 07:34 AM   #183
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Originally Posted by GnaGnaMan View Post
Ahh. Don't mind me. I'm drunk. When I sober up I will probably realize that the difference between speed and velocity here is not if the air streams into or out of the balloon.
We can pick this up when you are done with RBF.

The point is that I can fully inflate a balloon and then let it deflate in one second with air exiting at zero velocity and energy still conserved.

(Edit - if anyone is doubting I can do the above I will be happy to explain, or even demonstrate)
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Old 13th August 2019, 07:50 AM   #184
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Originally Posted by ponderingturtle View Post
No, the pressure in a partially inflated balloon is often higher than a fully inflated one because of properties of the tension in rubber and such. Think about blowing up a balloon when are you blowing hardest vs when is it easier that is a direct measurement of the pressure.
But that wouldn't mean that the pressure in the balloon would be related to the velocity of the escaping air by the Bernoulli equation would it?
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Old 13th August 2019, 05:14 PM   #185
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Originally Posted by GnaGnaMan View Post
Ahh. Don't mind me. I'm drunk. When I sober up I will probably realize that the difference between speed and velocity here is not if the air streams into or out of the balloon.
Incidentally, I hope that when you sobered up you recalled that Newton had a third law of motion.

(Edit: and yes, since you will probably ask, I do realise that the Bernoulli equation uses speed rather than velocity).
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Old 13th August 2019, 05:36 PM   #186
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Originally Posted by Ziggurat
The problem is probably mostly the reduction in thrust because of the nozzle size. The gradual expansion means the air flow will expand with the cone, and will decrease in velocity, leaving the cone at much lower velocity. If itís, say, a factor of 5 bigger diameter, thatís a factor of 25 more in area, so a factor of 25 less in exit velocity and a factor of 25 less in force. At some point, the force wonít overcome friction.
Originally Posted by GnaGnaMan
Ok, I gotta back-peddle here.

This sounded like a really good explanation but it can't work. Eventually, it doesn't take any math. It's just simple conservation of energy. The energy involved comes from the stretched rubber and is converted into velocity of air escaping the balloon. If no energy is lost transferring the rubber energy to kinetic energy then the air must still end up at the same speed

Increased friction/turbulence from a larger nozzle is has already been mentioned as a potential issue.
I am interested to know if you have back-pedalled your back-pedal (and it is no criticism if you have, I have had to change my position in this thread too).

From what RDF has said and given your answer to him, are we all on the same page that there will be a decrease in velocity as Ziggurat originally said?
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Old 13th August 2019, 10:13 PM   #187
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My next guess is that in a vacuum the velocity of the air would not decrease, in fact it might increase (due to the backward 'bounce' some of the air will get from the sides of the cone.

I am happy to be shot down on that one.
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Old 13th August 2019, 11:58 PM   #188
GnaGnaMan
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Originally Posted by Red Baron Farms View Post
Long winded way to simply say ABDC, but it is correct. I happily apologize profusely. You actually are capable of learning when not building strawmen.
This was not a profuse apology. This was not an apology at all.
I will break this off here. You win the argument. You remain a graveyard for BS.
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Old 14th August 2019, 12:00 AM   #189
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Originally Posted by Robin View Post
We can pick this up when you are done with RBF.

The point is that I can fully inflate a balloon and then let it deflate in one second with air exiting at zero velocity and energy still conserved.

(Edit - if anyone is doubting I can do the above I will be happy to explain, or even demonstrate)
Please explain.
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Old 14th August 2019, 12:07 AM   #190
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Originally Posted by Robin View Post
I am interested to know if you have back-pedalled your back-pedal (and it is no criticism if you have, I have had to change my position in this thread too).
No, I don't see it.

Quote:
From what RDF has said and given your answer to him, are we all on the same page that there will be a decrease in velocity as Ziggurat originally said?
RBF obviously doesn't know what he is talking about. He is proposing a reactionless rocket that works by pushing off the atmosphere. Does that make any sense?

Originally Posted by Robin View Post
My next guess is that in a vacuum the velocity of the air would not decrease, in fact it might increase (due to the backward 'bounce' some of the air will get from the sides of the cone.

I am happy to be shot down on that one.
Yes, under certain conditions the velocity of the air increases as it exits the cone, while it's pressure decreases. This happens when the air flow through the narrow part reaches the speed of sound.
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Old 14th August 2019, 12:40 AM   #191
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It's peak internet when the rudest person in the discussion demands apologies from those being rude back to him.
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Old 14th August 2019, 12:57 AM   #192
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Originally Posted by GnaGnaMan View Post
RBF obviously doesn't know what he is talking about. He is proposing a reactionless rocket that works by pushing off the atmosphere.
What are you talking about? We are discussing a "rocket" that doesn't move at all.
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Old 14th August 2019, 01:27 AM   #193
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Originally Posted by GnaGnaMan View Post
Yes, under certain conditions the velocity of the air increases as it exits the cone, while it's pressure decreases. This happens when the air flow through the narrow part reaches the speed of sound.
Because pressure waves can't travel the other way, I believe.

Can't see how that is an issue in a vacuum.

As a pure geometry exercise I can't see why it does not increase the velocity (if only slightly) at slower velocities in a vacuum.
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Old 14th August 2019, 01:38 AM   #194
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Originally Posted by Robin View Post
It's peak internet when the rudest person in the discussion demands apologies from those being rude back to him.
And flounces out of the thread for a massive two minutes.

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Old 14th August 2019, 02:16 AM   #195
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Originally Posted by GnaGnaMan View Post


RBF obviously doesn't know what he is talking about. He is proposing a reactionless rocket that works by pushing off the atmosphere. Does that make any sense?
Still with the BS lies and rude strawmen? I never said that ever. In fact anyone who ever implied that even a little I clearly stated was wrong.

So once again you must have started drinking too much and disengaged your brain.

Back to unteachable drunk trolling again! What a shame. And so close too. Only a single step away from understanding the primary way the cone reduces the thrust from the balloon.

All you had left to do was apply the force vectors from the pressure differentials and see it for yourself!
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Old 14th August 2019, 02:39 AM   #196
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Originally Posted by Robin View Post
My next guess is that in a vacuum the velocity of the air would not decrease, in fact it might increase (due to the backward 'bounce' some of the air will get from the sides of the cone.

I am happy to be shot down on that one.
In a vacuum the exiting air might accelerate due to the pressure differentials. But remember, there is also less pressure on the balloon too. I have a feeling the net effect from all that would be minimal.

I too hope someone more knowledgeable about thrust in vacuum will chime in.
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Old 14th August 2019, 03:33 AM   #197
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Originally Posted by Robin View Post
What are you talking about? We are discussing a "rocket" that doesn't move at all.
First of all, excuse my hyperbole. I am aware that he is not proposing that. His theory implies it but he is not aware of that. Simply pointing it out and asking about it received no reaction, so I tried with some sting.

Here is RBF's theory:
Originally Posted by Red Baron Farms View Post
When the balloon is allowed to vent air through the cone as a simulated rocket engine, the air inside the cone drops in pressure. The air outside the cone is still 1 atmosphere. So the force outside the cone presses inwards against the cone. But the cone has an angle. So a % of the force is actually pushing backwards against the car. The simulated rocket engine pushes forward, the cone pushes backwards.

Now you may apply your conclusion. The net force is not enough to overcome friction. So the car doesn't move.
Now let's conclude. If we take away the forward push of the "simulated rocket engine" then the push of the atmosphere will push the whole contraption backwards.
We can just pipe the escaping air back into the balloon (with a pump to restore the pressure). That eliminates the thrust generated by "simulated rocket engine" but leaves the push of the atmosphere.

This is not rocket science (pun intended). IMHO, this is just a primitive fridge.
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Old 14th August 2019, 03:44 AM   #198
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Originally Posted by Robin View Post
Because pressure waves can't travel the other way, I believe.

Can't see how that is an issue in a vacuum.

As a pure geometry exercise I can't see why it does not increase the velocity (if only slightly) at slower velocities in a vacuum.
I don't understand what you are saying there. So here's just some general statement.
In a vacuum the pressurized air must reach the speed of sound at the narrow part and will further accelerate to supersonic speeds as it travels along the cone.
The key to understanding this is that the speed of sound depends on the properties of the medium.
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Old 14th August 2019, 03:49 AM   #199
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Originally Posted by Robin View Post
It's peak internet when the rudest person in the discussion demands apologies from those being rude back to him.
I am sure we have different standards of rudeness. When I asked you to "please explain", that was meant to be a polite request. Maybe that was not how it was understood, as you have ignored it. If there is anything I should do differently then you need only say so.
If it is less rude to denounce you as an incorrigible crank then I can do that. It's not less rude to me but you are apparently you are implying that it is to you.
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Old 14th August 2019, 04:20 AM   #200
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Originally Posted by GnaGnaMan View Post
I am sure we have different standards of rudeness. When I asked you to "please explain", that was meant to be a polite request.
I was obviously not talking about that. I was obviously talking about your continued childish strawmanning of RBF.

Perhaps I can charitably assume that you are still blotto, in which case perhaps we can continue this when you have a clearer head.
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