Brian-M
Daydreamer
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Split Thread The validity of classical physics (split from: DWFTTW)
- Thread starter Dan O.
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Suppose your hot-air balloon, with or without the Carnot cycle or what have you, were to actually travel at windspeed, which is clearly absurd. If you then fired the rockets to get it to 50 m/s, what would happen? Hot air ballons do not work in a vacuum, of course! And if you were traveling at "windspeed" alongside it and fired a bullet at the balloon, do you think that the gasbag would be unharmed and that the pilot of the balloon could merely pick up the projectile? You act as if drag and friction were one and the same, whereas they are actually opposites opposing gravity until the vectors are at a maximum. Or do you think that if you took away the river, then the boat would continue since there would still be no force? Hah! Even Archimedes understood this when it was only because of the force of buoyancy that he was able to run down the street naked shouting "Eureka!".
John Freestone
Graduate Poster
Humber, I have gone to the trouble of trying to discuss the balloon question with you in some detail, and twice asked a very important and specific question about what force keeps a balloon at below windspeed, in your opinion. You have not answered. I have also pointed out that you have stated that the balloon will travel at the mean speed of the wind, and suggested that this means you have recanted your earlier Newtonian heresy, despite continuing to reassert it, remind us of others, and introduce new ones. Perhaps my 'waffle' is too difficult for you. You seem to be ignoring me. A while back you told me to shut up. You probably have me on ignore, or 'fast scroll' at least. I think I've come to the end of my interest in your blatant trolling anyway. The following sums it up:
Your descriptions of the world break the laws of physics, as has been pointed out about ten times in the last two days by people who understand what they actually are. Yours is the lacking or flawed evidence (actually, just lacking as far as I can see; all you provide is your own garbage).
You demand examples of when things happen according to Newtonian mechanics, and use unrepresentative analogies to argue to the contrary when these are given. You let slip the very point you are arguing against, and then lack the balls to own up to the fact that you are wrong. You are wrong on almost every point you make.
The problem is that you won't apply the relevant knowledge that has been discovered over centuries, but must deny it, invent your own nonsense, and insult the intelligence of those who try to educate you.
If we insert a negative into the last part, as I have done, this describes the situation precisely (I think one of your disingenuous dodges in the past was actually to say that you accidentally missed a negation, but I don't think you did here! We describe Newton's world to you, and you insult us by suggesting that our description breaks Newton's laws).
Your descriptions of the world break the laws of physics, as has been pointed out about ten times in the last two days by people who understand what they actually are. Yours is the lacking or flawed evidence (actually, just lacking as far as I can see; all you provide is your own garbage).
You demand examples of when things happen according to Newtonian mechanics, and use unrepresentative analogies to argue to the contrary when these are given. You let slip the very point you are arguing against, and then lack the balls to own up to the fact that you are wrong. You are wrong on almost every point you make.
You seem to think that the first and last of these are equivalent for some reason. Your assertions have been denied, and by recourse to Newtonian mechanics. If you cannot think of any of them that have been denied, that is because you cannot think. They have not been agreed with, because they have been denied.
And you try to understand mechanical principles by thinking they are equivalent to electrical ones. [ETA: even when you do this, you don't understand electricity either, according to someone with a diploma in electrical engineering.]
The problem is that you won't apply the relevant knowledge that has been discovered over centuries, but must deny it, invent your own nonsense, and insult the intelligence of those who try to educate you.
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John Freestone
Graduate Poster
Thanks for that spork. You've entertained me so much in this thread and that made my morning.
I have a theory that the 'h' and 'b' are silent (without the 'b' it rhymes with 'dumber', of course, and the French drop the leading 'h' - there have been a lot of French words from him - faux, jejeune, ingenue...). It would be a fitting pronunciation, 'um-er'.
sol invictus
Philosopher
- Joined
- Oct 21, 2007
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My favorite tidbit there is velocity "Velocity (difference) = Drag x Force". The humberverse must be strange indeed with units like that...
I ignored this like most of the blizzard of wrong humberisms, but there is one mote of truth there - it is possible to make a rather precise analogy between some electrical and mechanical systems.
The classic example is an RLC circuit, which has a differential equation that is identical to that of a damped harmonic oscillator. The correct analogues are:
length/position = charge (e.g. on the capacitor)
velocity = time derivative of charge = current
mass = inductance
damping = resistance
spring stiffness = 1/capacitance
driving force = driving voltage
However the equations involved are very different from the one under discussion in this thread. For example wind resistance generally goes as velocity squared, whereas resistance in a circuit goes as current (e.g. V=IR, not V=I2R).
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A few startling facts about our universe for you, humber:
1) A hot-air balloon at windspeed experiences no aerodynamic drag force.
2) On a still day, a hot air-balloon has no way of moving laterally. It cannot trade off altitude for lateral speed.
3) A submarine (with the engines off) floating at the speed of the current experiences no hydrodynamic drag force.
4) Various boats and other floating objects (racing canoes, 55-gallon drums, kids in inner tubes, a bunch of empty milk bottles tied together, sailboats, etc.) will all float along at the same speed in a current, unless the air makes them do otherwise. If the speed of the wind matches the speed of the current, they will all float along at exactly the same speed.
5) A canoe moving at the speed of the current has no bow wake.
(In addition to my knowledge of science, I'll put up my four gold medals from the US Canoe Championships as a bit of cred on those last two points.)
1) A hot-air balloon at windspeed experiences no aerodynamic drag force.
2) On a still day, a hot air-balloon has no way of moving laterally. It cannot trade off altitude for lateral speed.
3) A submarine (with the engines off) floating at the speed of the current experiences no hydrodynamic drag force.
4) Various boats and other floating objects (racing canoes, 55-gallon drums, kids in inner tubes, a bunch of empty milk bottles tied together, sailboats, etc.) will all float along at the same speed in a current, unless the air makes them do otherwise. If the speed of the wind matches the speed of the current, they will all float along at exactly the same speed.
5) A canoe moving at the speed of the current has no bow wake.
(In addition to my knowledge of science, I'll put up my four gold medals from the US Canoe Championships as a bit of cred on those last two points.)
CORed
Penultimate Amazing
It seems likely. The ones that disappear from the dryer in our universe must go somewhere
It seems likely. The ones that disappear from the dryer in our universe must go somewhere
And by a similar law of symmetry, I suspect I now know who the guy at our local jack in the box is talking to when I hear him having half of a very passionate conversation about physics that doesn't seem to describe our universe.
It's gotta be a good day if we've solved that and the age old "sock question" before 8:00am.
Yes, I know that, but "absolute" force does make a difference. In the case of the book on the table, increasing the force applied to the book means that it is met with an equal but opposing force, but the friction between the book and table increases. The items will become compressed, so energy will be stored and so forth. OK, they don't move, but a lot of other things change.
That expression would be fine by me, as long as it can be accepted that just because a balance is there, it does not mean that no work is being done. Either way, I could look at the treadmill and say there is no force or work.
The electromagnetic energy radiated by the sun can tell you a lot about it.
In the case of the free falling object, the friction generates the heat, so there must be work being done.
If there were no gravity, then there would be no acceleration, velocity or heat. Gravitational force is necessary to those effects.
Then I suppose the quest is now for wind or water borne objects that travel w.r.t the ground or within a flow, that do not require work be done on them.
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Excellent! An adventure... like the quest for the Holy Grail - only somewhat more brief, because I just solved it...
Anything floating along in a steady stream that has reached steady state has no work being done on it - in any frame at all.
But we can still have fun looking for that grail.
John Freestone
Graduate Poster
I was thinking that if I tried to sellotape the two ideas together at all I'd have put voltage as standing for mechanical force and current as velocity (or acceleration or momentum, or anything involving motion). I think he likes it that way because velocity and voltage both start with a 'v'.
I would have thought this formula was more appropriate though.
Yes
Yes, and you are right that it is a simplification.
I made it so in my example, that's all. There is a minimum differential velocity required to maintain a specific force.
Yes, I know that. That is why zero KE, though possible, cannot be a useful condition.
Yes, a kinematic case, where force is simply "applied", not the same sort of problem at all.
The force from a parachute that is restrained by its load (brake on) is dependent upon the relative velocity of the parachute w.r.t the wind, but also the static pressure, which may give a higher peak force. Once underway, the falls a bit to become the dynamic force. That is the initial condition.
You say that the force will be generated (though falling) as long as there is a differential wind of some sort.
No. The reason there are no wind-blown objects that reach winspeed, is that the opposing drag forces become greater than any parachute can provide, regardless of its relative velocity w.r.t the wind.
This is certainly true of air resistance. That force is at least the square of the velocity, yet the parachute force is perhaps a linear function of velocity, so obviously the drag will dominate.
Also, the parachute itself, will experience drag, and that too is related to V^2. That alone, regardless of load, means that wind velocity is not possible. Unloaded, yet formed parachutes, do not reach windspeed.
John Freestone
Graduate Poster
Ah, that reminds me, which bit of the ground are you taking as your 'boss'? See, if you want to be clear about such amazing details as you're interested in in the rest of this post, like forces adding to zero being different from no force, then you yourself are travelling without any work being done, when your motion is considered with respect to any other bit of ground than the one you're standing on. In fact, you're even moving w.r.t. that bit of ground. The Earth is revolving on its axis, and you don't do any work to keep up with that motion, but each bit of it is changing its position with respect to the others. I'm in Britain. The bit of the Earth on the opposite side of it, somewhere in NZ, is travelling at over 2000 miles per hour w.r.t. me (hi ynot!).
Nine - nil (ok, I didn't post a link for that yet. would you like me to?). On the other hand, I only started counting the other day and you've been talking codswallop for a month.
The esteemed publisher, Springer Verlag, have a series of books on electrical models that strongly suggest that you don't know what you are talking about.
ETA:
Re link;
There are semiconductor devices in your mobile phone that are psuedomorphic, and available in industrial quantities. Ignorance is painful, John.
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John Freestone
Graduate Poster
Thank you for alerting me to that. I'll sue them for libel.
Are but they don't run on pseudoenergy, if I'm not very much mistaken, otherwise known as newagenergy. If you had read the article I linked to...
Take the cure then and stop complaining.
John Freestone
Graduate Poster
...apart from the ones that exceed it, like hot air balloons, but they're pushed by their heat engines, so they go at some fixed percentage less than 100% of windspeed or more, and always at the mean velocity of the wind...blah, something to do with parachutes that I wikkied...
John Freestone
Graduate Poster
Pardon me quoting myself, but now I've had a moment to check, my version would be this:
Force (F) -> Voltage (V) (it is, after all, the electrical force in yer batteries)
Acceleration (a) -> Current (I)
Mass (m) -> Resistance (R)
a = F/m
I = V/R
But the whole 'model' idea is fairly banal anyway, and electrical equations certainly can't be used to prove mechanical ones wrong, as humber was trying to do.
John Freestone
Graduate Poster
Once again, then, I ask, if drag is not the force of the wind that accelerates a balloon, what is the force that does accelerate it? We can call it something else: humber's mystery force, if you like. Drag is dissipative, you say, so it reduces the balloon's velocity as it floats in the wind, have I got that right? That must be the drag that keeps it below windspeed, I suppose? So what's humber's mystery force accelerating the balloon? When we first let it loose from the field, there's presumably drag of the air, which you say will slow it down. How does it go slower than stopped? So many questions.
Sorted, although I don't know much about negative lengths. I didn't have enough room for your gems.
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Dan O.
Banned
- Joined
- Feb 14, 2007
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- 13,594
Just for fun, I setup a 1 dimensional simulation of a boat in water. The simulation shows just what the first order equasions expect: The boat never stops moving but its velocity decays exponentially.
However, when I replace the perfect water with random size particles [a uniform distribution with the same mean], the boat does stop and even begins moving backwards
However, when I replace the perfect water with random size particles [a uniform distribution with the same mean], the boat does stop and even begins moving backwards
John Freestone
Graduate Poster
When you asked why a cart doesn't just go at windspeed without a prop (I think - 'or a sail' you said), and I said 'Friction', that is of course the dissipative, lossy friction of the rolling resistance (scrubbing on tyres), friction of bearings and so on. Just as per balloon, however, the drag is the acceleration force.
When you drive a car through the air, the drag retards motion. There's no change of action. While relative velocity exists between a medium and a body immersed in it, drag will accelerate the body - in the direction of flow relative to the body. Simultaneously, the same force (I can't be doing with these stupid pairs
) will accelerate the mass of the medium in contact with the body - in the direction the body is moving w.r.t. the medium.
That was just for the benefit of anyone who gives a toss about Newtonian mechanics.
When you drive a car through the air, the drag retards motion. There's no change of action. While relative velocity exists between a medium and a body immersed in it, drag will accelerate the body - in the direction of flow relative to the body. Simultaneously, the same force (I can't be doing with these stupid pairs
) will accelerate the mass of the medium in contact with the body - in the direction the body is moving w.r.t. the medium.That was just for the benefit of anyone who gives a toss about Newtonian mechanics.
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