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Old 10th August 2019, 03:11 AM   #121
Robin
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Originally Posted by GnaGnaMan View Post
Here's a quote from RBF:

According to him, it does not matter if we are dealing with a cone.
Are you avoiding my question? Are you doubting that blowing in the narrow end of a plastic cone hard enough will collapse it?
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Old 10th August 2019, 03:19 AM   #122
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Incidentally it will also work with a straw.

But what is the cling film for? I don't understand that. Blowing through a flimsy straw will also collapse it.
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Old 10th August 2019, 03:26 AM   #123
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Originally Posted by Robin View Post
Are you avoiding my question? Are you doubting that blowing in the narrow end of a plastic cone hard enough will collapse it?
Ok, if you want to change the subject...

I am not sure under which conditions a cone would collapse. I guess the air coming from the narrow end would have to be low pressure compared to ambient and quite fast. Obviously this will not always be the case, eg in a vacuum.

If you think it will help, post a video to support your understanding. It is what OP did, so why shouldn't you?
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Old 10th August 2019, 03:28 AM   #124
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Originally Posted by Robin View Post
Incidentally it will also work with a straw.

But what is the cling film for? I don't understand that. Blowing through a flimsy straw will also collapse it.
I was not able to collapse a straw, so I tried something with less stiffness.
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Old 10th August 2019, 03:32 AM   #125
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Conspiracy Catz took a look at a similar flat Earther experiment using a perforated and non perforated tube nozzle on an air rocket,

https://www.youtube.com/watch?v=4lu3lrq9R4o
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Old 10th August 2019, 03:53 AM   #126
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Apparently I have discovered a brand new physical principle

I think I will name it after my dog, Bernoulli.
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Old 10th August 2019, 03:59 AM   #127
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Originally Posted by Robin View Post
Apparently I have discovered a brand new physical principle

I think I will name it after my dog, Bernoulli.
Yes, apparently. But you should chose a different name. That one is already taken.
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Old 10th August 2019, 04:08 AM   #128
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Here's my take on the Bernoulli effect in relation to OP.

But let's ignore the cone. Let's just take a balloon with a straight pipe for a mouth piece. We have the air inside the balloon, inside the pipe, and outside of both.

We fill the balloon and hold the mouth piece closed. The air inside the balloon is compressed by the balloon. It has higher pressure than the outside air. The over-pressure stores energy

You have air molecules from inside the balloon hammering against the skin of the balloon and against the finger you use to hold it closed. These air molecules are deflected back towards the inside of the balloon. They push back against the air molecules further away from skin and so on.

When you remove your finger the air starts to escape. The air molecules are no longer deflected back. That means they do not push back. That means less pressure. (Strictly speaking there is still be some pushback as faster air molecules will bounce off slower molecules.)

That means that the general bouncing around of the air molecules turns into movement through the pipe. Pressure is turned into movement.
Energy that was stored as (over-)pressure is converted into kinetic energy. Because of energy conservation, more speed must equal less pressure.

That's how the Bernoulli effect happens.

The logic here holds regardless of what kind of balloon we use. A balloon with a tougher skin will compress the air more, creating more overpressure. We could also use a steel pressure vessel with massively high pressure or just barely above atmospheric.

Now we know about the relation between the air inside the balloon and inside the pipe. But what about the pipe and the outside?

Well, arguments about energy conservation won't help us because there is more energy stored in the pressurized air inside the balloon. Mechanical arguments don't go anywhere, either. So what if a bunch of air molecules has a collective, net sideways motion. That doesn't tell us how hard these molecules bounce sidewards.

Once the air exits the tube you will have a gust of air travelling through the room. This moving packet of air travels relative to the rest of the air in the room. But does that mean that it has lower pressure?
Of course not. If it did, then we would expect it to "suck" in more air to equalize the pressure. Even if that happened initially, it would end pretty quickly and then we'd be left with just movement.
The moving air is obviously at the same pressure as the surrounding air. It just happens to be moving. It has kinetic energy which the surrounding air does not have. It has altogether more energy.
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Old 10th August 2019, 08:10 AM   #129
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Originally Posted by GnaGnaMan View Post
Here's a quote from RBF:

According to him, it does not matter if we are dealing with a cone.
Don't put words in my mouth. THE WHOLE EFFECT IS PRECISELY BECAUSE IT IS A CONE! They created a venturi of sorts. The balloon is wide, and the end of the cone is wide and the parts touching the car narrow.

Not much different than the venturi on a carb, except it is pushing from the balloon end rather than sucking from the cone end. Same low pressure on the outside of the paper cone, and that vectors a force against the thrust vector exiting the balloon. The two forces working counter to each other. Thus the car remains stationary.
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Old 10th August 2019, 08:59 AM   #130
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Originally Posted by Red Baron Farms View Post
Don't put words in my mouth. THE WHOLE EFFECT IS PRECISELY BECAUSE IT IS A CONE! They created a venturi of sorts. The balloon is wide, and the end of the cone is wide and the parts touching the car narrow.
Hang on...
Will blowing into a straw cause it to be squeezed by ambient air pressure?
That is implied by your quote. Did I misunderstand you there?
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Old 10th August 2019, 11:06 AM   #131
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Originally Posted by GnaGnaMan View Post
Hang on...
Will blowing into a straw cause it to be squeezed by ambient air pressure?
That is implied by your quote. Did I misunderstand you there?
I NEVER MENTIONED A STRAW OR TUBE.

It is theoretically possible to pressurize a long tube by blowing air in faster than it can easily escape out the other end. Whether or not human lungs could pressurize it that much I really don't know. I doubt it. That is a completely different sort of effect than is shown in the car/balloon/cone vid.

In the vid we have air higher than atmospheric in the balloon, and air lower than atmospheric in the cone, and the forces from that cancel out causing the car to remain stationary. ie the balloon pushes the car forward and the cone pushes the car backwards and the result is it stands still.

This is a clear example showing that in ATMOSPHERE the cone can cancel the effects of simulated rocket propulsion.

In fact if we did this little experiment in a vacuum, we would expect the car to move like the first time....maybe even better!

So the vid is woo.
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Old 10th August 2019, 11:25 AM   #132
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Originally Posted by Red Baron Farms View Post
I NEVER MENTIONED A STRAW OR TUBE.
I'm not sure why you feel the need to emphasize that.

Quote:
It is theoretically possible to pressurize a long tube by blowing air in faster than it can easily escape out the other end. Whether or not human lungs could pressurize it that much I really don't know. I doubt it. That is a completely different sort of effect than is shown in the car/balloon/cone vid.
Blowing air through a tube means that the air in the tube is flowing faster than calm air outside the tube.
Does this mean that the air in the tube is at lower pressure than the outside air? Yes or no?

Quote:
In the vid we have air higher than atmospheric in the balloon, and air lower than atmospheric in the cone, and the forces from that cancel out causing the car to remain stationary. ie the balloon pushes the car forward and the cone pushes the car backwards and the result is it stands still.
Wrong.

Quote:
This is a clear example showing that in ATMOSPHERE the cone can cancel the effects of simulated rocket propulsion.

In fact if we did this little experiment in a vacuum, we would expect the car to move like the first time....maybe even better!
I understand that you, personally, would expect that.
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Old 10th August 2019, 01:27 PM   #133
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Originally Posted by GnaGnaMan View Post
I'm not sure why you feel the need to emphasize that.
because you changed the problem then pretended it had something to do with something I claimed. I did not say it. It is not part of the problem. You are being willfully ignorant in building up a stupid strawman to the effect.


Originally Posted by GnaGnaMan View Post
Blowing air through a tube means that the air in the tube is flowing faster than calm air outside the tube.
Does this mean that the air in the tube is at lower pressure than the outside air? Yes or no?
Not part of this problem. I just said that I don't know and there is not enough information for me to know for sure. What part did you miss? This video is not about tubes. Under certain circumstances a tube can be part of a venturi though.

Originally Posted by GnaGnaMan View Post
Wrong.
Robin already proved this for herself. The phenomenon is also proved in (wikipedia list)
Quote:
The Venturi effect may be observed or used in the following:
  • Cargo eductors on oil product and chemical ship tankers
    Inspirators that mix air and flammable gas in grills, gas stoves, Bunsen burners and airbrushes
    Water aspirators that produce a partial vacuum using the kinetic energy from the faucet water pressure
    Steam siphons using the kinetic energy from the steam pressure to create a partial vacuum
    Atomizers that disperse perfume or spray paint (i.e. from a spray gun).
    Carburetors that use the effect to suck gasoline into an engine's intake air stream
    Wine aerators, used to infuse air into wine as it is poured into a glass
    The capillaries of the human circulatory system, where it indicates aortic regurgitation
    Aortic insufficiency is a chronic heart condition that occurs when the aortic valve's initial large stroke volume is released and the Venturi effect draws the walls together, which obstructs blood flow, which leads to a pulsus bisferiens.
    Protein skimmers (filtration devices for saltwater aquaria)
    In automated pool cleaners that use pressure-side water flow to collect sediment and debris
    The barrel of the modern-day clarinet, which uses a reverse taper to speed the air down the tube, enabling better tone, response and intonation[citation needed][5]
    Compressed air operated industrial vacuum cleaners
    Venturi scrubbers used to clean flue gas emissions
    Injectors (also called ejectors) used to add chlorine gas to water treatment chlorination systems
    Steam injectors use the Venturi effect and the latent heat of evaporation to deliver feed water to a steam locomotive boiler.
    Sandblasting nozzles use Venturi effect to accelerate air and media mixture.
    Emptying bilge water from a moving boat through a small waste gate in the hull—the air pressure inside the moving boat is greater than the water sliding by beneath
    A scuba diving regulator to assist the flow of air once it starts flowing
    In recoilless rifles to decrease the recoil of firing
    Ventilators
    The diffuser on an automobile
    Race cars utilising ground effect to increase downforce and thus become capable of higher cornering speeds, from the late 1970s until such technology was banned from competition in the early to mid-1980s
    Large cities where wind is forced between buildings - the gap between the Twin Towers of the original World Trade Center was an extreme example of the phenomenon, which made the ground level plaza notoriously windswept.[6] In fact, some gusts were so high that pedestrian travel had to be aided by ropes.[7]
    In windy mountain passes, resulting in erroneous pressure altimeter readings[8]
    The leadpipe of a trombone, affecting the timbre
    Foam proportioners used to induct fire fighting foam concentrate into fire protection systems
    Trompe air compressors to entrain air into a falling column of water
    The Mistral wind in Southern France increases in speed through the Rhone valley.
    Low-speed wind tunnels can be considered very large Venturi because they take advantage of the Venturi effect to increase velocity and decrease pressure to simulate expected flight conditions.[9]
So if I am wrong, then I have a whole lot of company being wrong. And you being right? Along with who? Flat Earthers?



Originally Posted by GnaGnaMan View Post
I understand that you, personally, would expect that.
Yes I would. And it has been shown to you mathematically by abaddon, experimentally by robin, the physics explained by Zig, Dave, and others, and I personally simplified it down to the level any 5th grader could understand. Yet you persist in your woo understanding of the problem. So apparently you wouldn't be doing very well on the show.
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Old 10th August 2019, 02:06 PM   #134
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Originally Posted by GnaGnaMan View Post
Maybe you could expand on this. There are literally no google hits for "triple cone injector".
Perhaps you could follow the link in the previous post you replied to:

Originally Posted by Dave Rogers View Post
I suggest those who want their minds expanded look at a classic example of conical nozzles in action, the triple cone injector.

Originally Posted by GnaGnaMan View Post
Originally Posted by Dave Rogers View Post
Therefore, it's a practical example of the phenomenon you were calling into question - that a jet through a cone can be at lower pressure than ambient at the narrow end, and at higher than ambient at the wide end.
I did no such thing.
Not true:

Originally Posted by GnaGnaMan View Post
This is wrong, as Zig pointed out, but I think it bears highlighting.
If the air inside the cone had less pressure than the surrounding atmosphere, the air from the atmosphere would enter the cone.
You did precisely such a thing. And since you seem uninterested in either learning anything, or even being honest enough not to deny your own statements, I think I have nothing more to say.

Dave
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Old 11th August 2019, 02:24 AM   #135
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Originally Posted by Red Baron Farms View Post
because you changed the problem then pretended it had something to do with something I claimed. I did not say it. It is not part of the problem. You are being willfully ignorant in building up a stupid strawman to the effect.
Please don't lie about me.

Quote:
Not part of this problem. I just said that I don't know and there is not enough information for me to know for sure. What part did you miss? This video is not about tubes. Under certain circumstances a tube can be part of a venturi though.
Is the information you need that the gas can be assumed to incompressible? I'm pretty sure that holds when dealing with breath. But perhaps we should come back to that later.

How about this instead:
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.
Bundle of misconceptions there. Suppose we take away the thrust. We block the wide end of the cone. To allow air to escape we punch 2 holes in either side at the widest part of the cone where we put the block. So instead of air escaping out the back it escapes both left and right, perpendicular to the former direction.
Conventional physics would hold that the car won't move.
However, the amazing new physics presented here suggest that the car will actually move backwards because there is still that supposed force pushing on the cone which is now no longer balanced by the thrust.


Quote:
Robin already proved this for herself. The phenomenon is also proved in (wikipedia list)

So if I am wrong, then I have a whole lot of company being wrong. And you being right? Along with who? Flat Earthers?
It would help if you presented this in the form of a logical argument. That would make it easier to see if what you trying to conclude from your "evidence" actually follows from the evidence.

Quote:
Yes I would. And it has been shown to you mathematically by abaddon, experimentally by robin, the physics explained by Zig, Dave, and others, and I personally simplified it down to the level any 5th grader could understand. Yet you persist in your woo understanding of the problem. So apparently you wouldn't be doing very well on the show.
That's nonsense on too many levels to unpack. Just apologize and we won't talk about it anymore.
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Old 11th August 2019, 02:32 AM   #136
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Originally Posted by Dave Rogers View Post
Perhaps you could follow the link in the previous post you replied to:
There is no mention of a triple cone injector on wikipedia either.
Why are you doing this? So you misremembered the name of something. So what? Just correct yourself.

Quote:
Not true:

You did precisely such a thing.
Please don't ignore my correction/clarification:
Originally Posted by GnaGnaMan View Post
Yes, that seems right. It would be a coincidence, though, and not relevant to the point.
...
Quote:
And since you seem uninterested in either learning anything, or even being honest enough not to deny your own statements, I think I have nothing more to say.
That's probably for the best.
I have talked a lot to people with non-mainstream ideas but you and RBF are quite possible the rudest I've ever encountered.
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Old 11th August 2019, 02:39 PM   #137
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Originally Posted by Ziggurat View Post
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.
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.
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Old 11th August 2019, 03:15 PM   #138
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Originally Posted by GnaGnaMan View Post
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.
Conservation of energy does not imply conservation of velocity because energy involves more than velocity.
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Old 11th August 2019, 03:18 PM   #139
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Originally Posted by Ziggurat View Post
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 View Post
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.
Interesting that you can't see it GnaGnaMan. Makes perfect sense to me.

It just occurred to me that if this experiment were carried out in a vacuum, the thrust of the jet of air would not be diminished by adding the cone. As the air left the nozzle it would just shoot out unimpeded, as there would be no air in the cone to mingle with.

Confirmation that rockets work better in space.
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Old 11th August 2019, 03:21 PM   #140
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Originally Posted by Robin View Post
Conservation of energy does not imply conservation of velocity because energy involves more than velocity.
What are you getting at?
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Old 11th August 2019, 03:26 PM   #141
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Originally Posted by Thor 2 View Post
Interesting that you can't see it GnaGnaMan. Makes perfect sense to me.
Yes, it made perfect sense to me, too. That's why I'm back-peddling.
The problem is that it makes the implicit assumption that the air exiting the balloon does so at the same rate regardless of whether the cone is installed.
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Old 11th August 2019, 03:35 PM   #142
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Originally Posted by GnaGnaMan View Post
Yes, it made perfect sense to me, too. That's why I'm back-peddling.
The problem is that it makes the implicit assumption that the air exiting the balloon does so at the same rate regardless of whether the cone is installed.
But it exits the cone at a much reduced velocity so the energy is much less. The energy has largely been absorbed by the air in the cone exerting a restraining force that decelerates the air as it leaves the nozzle.
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Old 11th August 2019, 03:47 PM   #143
GnaGnaMan
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Originally Posted by Thor 2 View Post
But it exits the cone at a much reduced velocity so the energy is much less. The energy has largely been absorbed by the air in the cone exerting a restraining force that decelerates the air as it leaves the nozzle.
Well, it may exit at reduced velocity (don't remember the video, tbh). And if it does then it is reasonable to suppose that it was absorbed by the air in the cone (via turbulence) but I wouldn't jump to that conclusion.
However, that does not follow from the argument about the widening cone. You would also get friction in a pipe.
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Old 11th August 2019, 03:54 PM   #144
Robin
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Originally Posted by GnaGnaMan View Post
What are you getting at?
My statement was quite plain.

You inferred that because of conservation of energy the velocity should not change.

I was pointing out that this is a flawed inference because energy is not just velocity.
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Old 11th August 2019, 03:56 PM   #145
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OK, I made a "Cone" with a rolled up sheet of printer paper and put it to my lips and blew. It rapidly turned into a soggy mess and started to collapse in on itself. It occurs to me that this might be happening when pete or peter shoves the paper cone up into the straw. That end of the cone becomes like a reed valve of sorts.*





*use to be "big" with the ***SNEER*** 2-stroke set.
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Old 11th August 2019, 03:59 PM   #146
GnaGnaMan
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Originally Posted by Robin View Post
My statement was quite plain.

You inferred that because of conservation of energy the velocity should not change.

I was pointing out that this is a flawed inference because energy is not just velocity.
It sounds like you may be invoking friction. But I did mention that possibility. Did you miss that?
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Old 11th August 2019, 04:23 PM   #147
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Originally Posted by GnaGnaMan View Post
It sounds like you may be invoking friction. But I did mention that possibility. Did you miss that?
Who mentioned friction?

I simply pointed out that your claim that conservation of energy implied conservation of velocity is wrong.

You are starting from a false premise, so the details that follow are irrelevant.
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Old 11th August 2019, 04:27 PM   #148
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Originally Posted by Elagabalus View Post
OK, I made a "Cone" with a rolled up sheet of printer paper and put it to my lips and blew. It rapidly turned into a soggy mess and started to collapse in on itself. It occurs to me that this might be happening when pete or peter shoves the paper cone up into the straw. That end of the cone becomes like a reed valve of sorts.*
Hmm, surprised at the pushback I am getting on this.

OK, I will repeat this with a bicycle pump if there are doubters that the air travelling quickly through the cone will decrease the pressure on the inside of the cone.

Will that satisfy everyone?
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Old 11th August 2019, 04:33 PM   #149
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Originally Posted by Robin View Post
Who mentioned friction?
Me (and a couple others before me who really deserve the credit).

Quote:
I simply pointed out that your claim that conservation of energy implied conservation of velocity is wrong.

You are starting from a false premise, so the details that follow are irrelevant.
Maybe you should have a look at this Bernoulli principle thing.
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Old 11th August 2019, 05:22 PM   #150
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Originally Posted by GnaGnaMan View Post
Me (and a couple others before me who really deserve the credit).
So when I made a clear statement that didn't mention friction, you assumed I must be talking about friction, rather than what I actually said, because you and a couple of other people had mentioned friction.

Quote:
Maybe you should have a look at this Bernoulli principle thing.
Maybe you should stop always kicking things into the long grass and explain why you think that conservation of energy implies conservation of velocity.
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Old 11th August 2019, 05:26 PM   #151
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Friction and turbulence are obviously factors that contribute to the overall sum of forces.

It is not an either/or situation.
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Old 11th August 2019, 05:30 PM   #152
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That brings me back to DevilsAdvocate's original question when he asked what was wrong with the logic.

The first thing wrong with the logic was the assumption that the change in structure involved in adding the cone ought not to change the sum of forces acting on the video.

Of course it will change that sum of forces.

The second and most important thing wrong with the logic is that nobody has explained how any of this could possibly imply that rockets don't work in a vacuum.
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Old 11th August 2019, 05:45 PM   #153
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Originally Posted by GnaGnaMan View Post
Maybe you should have a look at this Bernoulli principle thing.
Let's just check we are talking about the same thing:
Quote:
In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy
Yes?

This would imply that if you pass a stream of air through a cone then the pressure on the inside of the cone would decrease.

This would mean that if the cone was in an atmosphere, there would be a greater pressure on the outside surface than on the inside.

And you appear to have been busily denying that this would be the case.

So, perhaps it is you who should have a look at the Bernoulli Principle thing.
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Old 11th August 2019, 06:22 PM   #154
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Originally Posted by Robin View Post
So when I made a clear statement that didn't mention friction, you assumed I must be talking about friction, rather than what I actually said, because you and a couple of other people had mentioned friction.
I assumed you were talking about friction because that is what it "sounds" like. I am still not able to interpret it differently.

Quote:
Maybe you should stop always kicking things into the long grass and explain why you think that conservation of energy implies conservation of velocity.
Nothing you said until now sounded like a question to me or as if clarification was required but ok. There isn't much I can add in any case.
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. Ultimately the air ends up at atmospheric pressure. Thus the final speed depends on the over-pressure determined by the pull of the rubber.

Originally Posted by Robin View Post
So, perhaps it is you who should have a look at the Bernoulli Principle thing.
I have. Unfortunately you weren't able to help me with my questions, so I had to.
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Old 11th August 2019, 06:59 PM   #155
Robin
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Originally Posted by GnaGnaMan View Post
I assumed you were talking about friction because that is what it "sounds" like. I am still not able to interpret it differently.
So when I say "Conservation of energy does not imply conservation of velocity because energy involves more than velocity.", which seems perfectly true to me and would be true even if there were no friction, all you can get out of that is "something, something friction"?

I suggest that your inability to understand that simple statement is not my fault.
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Old 11th August 2019, 07:03 PM   #156
Robin
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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. Ultimately the air ends up at atmospheric pressure. Thus the final speed depends on the over-pressure determined by the pull of the rubber.
For a start, do you mean "speed" or "velocity"? They are different and the difference matters in this case. The force exerted is a function of velocity, not speed.
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Old 11th August 2019, 07:11 PM   #157
GnaGnaMan
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Originally Posted by Robin View Post
So when I say "Conservation of energy does not imply conservation of velocity because energy involves more than velocity.", which seems perfectly true to me and would be true even if there were no friction, all you can get out of that is "something, something friction"?

I suggest that your inability to understand that simple statement is not my fault.
Does it really have to be someone's fault? Ok, let it be mine, if it helps.

Originally Posted by Robin View Post
For a start, do you mean "speed" or "velocity"? They are different and the difference matters in this case. The force exerted is a function of velocity, not speed.
The relevant Bernoulli equation describes a 1-dimensional stream.
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Old 11th August 2019, 08:01 PM   #158
Robin
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Originally Posted by GnaGnaMan View Post
Does it really have to be someone's fault?
In order to make progress then we must find out why you are unable to understand what I said.

In order to do so we must first establish whether I was not clear enough or whether you didn't try hard enough to understand.

Saying 'its no-ones fault' is no use if you still don't understand what I said.
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Old 11th August 2019, 08:03 PM   #159
Robin
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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.


The relevant Bernoulli equation describes a 1-dimensional stream.
There is also a difference between speed and velocity in one dimension, so can you please tell me which you mean!
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Old 11th August 2019, 08:11 PM   #160
Elagabalus
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Originally Posted by Robin View Post
Hmm, surprised at the pushback I am getting on this.

OK, I will repeat this with a bicycle pump if there are doubters that the air travelling quickly through the cone will decrease the pressure on the inside of the cone.

Will that satisfy everyone?
Did Pete and Peter use a bicycle pump? Presta or Schrader?
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