Split Thread The validity of classical physics (split from: DWFTTW)

[humber]

I'd like to add a bit more detail just to make sure the statement is perfectly clear.

I agree that if the cart is going back with the belt at belt speed, the cart experiences the same force because of the relative movement between it and the surrounding air as it would when it is at a standstill outside at rest w.r.t. the ground while a tailwind with the same relative velocity as what the belt provided is blowing across the ground.

Sorry, Mender. I just noticed this post.
If both objects have enough friction to the ground/belt to prevent motion, yes.

I agree that this is equivalent. I hope that from this point forward we can agree to this as a starting point for any further discussion if at some point we disagree.

OK.

Now for the next statement.
Let's start with the battery powered car sitting on the ground outside. Add radio controls for convenience, and put an anemometer on top of the car. Add also telemetry to allow remotely recording of the speed of the wheels, the power draw of the electric motor and the anemometer readings. Let's use the now conventional 10 mph tailwind as a baseline.

OK

The RC car is off. The tailwind is blowing at 10 mph. The anemometer faithfully records that and sends that result via telemetry to a laptop. It says that there is a wind blowing at 10 mph from behind the car. No wheel speed and no power draw.

OK

What is the anemometer telling us? It tells us that when the car was at a standstill on the ground, the air was moving at 10 mph. Since air has mass, the anemometer is also measuring one of the components needed to compute the KE of the air w.r.t the car and the anemometer. For a given volume of air moving by, we can calculate the amount of KE in the air. Let's say that the air volume measured has the same mass as the car. Let's also say for convenience the KE as calculated has a nominal unit of one .

OK. It computes it, but absorbs only a little.

Start the car moving forward until the anemometer reading is zero. The wheel speed is now showing 10 mph and there is a specific amount of electric power being used to move the car at 10 mph.

OK

Now what is the anemometer telling us? It tells us that when the car is moving forward at the same speed as the air, both at 10 mph, the air has zero KE. How can that be? Where did the KE go? Did the anemometer suddenly stop working? The car now has a KE of one. That came from the car moving along the ground, as we can plainly see.

That is not a valid deduction. You infer the KE from anemometer. That does no tell you that there is no KE, but that it is not registered by the anemometer. The KE is now in the car, but that does not come from the wind. There is no causal connection between the anemometer and the car's KE. The anemometer is simply mounted on the car. It's the motor that tells the story.

Did the KE of the air somehow get exchanged for the car's KE? Could that possibly happen under the right circumstances? Maybe we'll get to that later. For now, let's do some more testing.

No, it is not exchanged if the car is motorised. Some energy will be exchanged as the wind pushes the car, but cars are not efficient sails, so most of the work will come from the motor. The energy, from the battery.

Let's pick up the car without changing the power setting (recorded) and take the car inside and place it on a treadmill, carefully adjusting the treadmill belt speed to match the car's wheel speed so that the car stays in place on the treadmill. Once we have successfully achieved that balance, we check the telemetry to make sure that the wheel speed of the car is exactly that same. The anemometer is reading correctly (still zero), showing that the air in the room isn't moving and therefore has no KE. Still no idea as to where the KE of the air went.

Nor the car. It has not been accelerated, so no KE has been absorbed, or exchanged. In this case, the car is only overcoming the friction, to stay where it is.

But now the car isn't moving, so it can't have any KE even though the wheels are still spinning and the power draw is exactly the same as it was outside at 10 mph in a 10 mph tailwind.

It's not moving, but the power is a lot less.

Now we lost the KE of the car too! How could we be so careless! Where did the KE of the car go? Or is this treadmill thing just an elaborate hoax to cleverly hide the KE to trick people?

No KE is present. If it had KE, it would be moving relative to something which can provide a reactive force. The belt "gives" against the drive wheels. It is effectively on a static dyno, with a very small load. It is not likely to be stable, and could go either way.

The low friction of the RC car on the belt? That can't possibly be an issue; the telemetry confirmed that the conditions are exactly the same for the RC car when outside running at 10 mph across the ground in a 10 mph tailwind as when the car is maintaining station on a treadmill running at 10 mph in a room of still air. Yet all the KE disappeared! Did it slide away on the belt somehow?

No. The telemetry will not confirm that. You need to check the motor's consumption. A car in wind will consume more than the car on the belt.
In the wind, you will see the motor consume energy as it accelerates the car's mass (KE) and loses it to the forces of drag. Both will increase as long as the car is accelerating. If you stop accelerating at windspeed, then the load will be drag (all frictional losses) only. This will require a constant demand from the motor in order to keep it at that speed, and will also be at a maximum.

If the car is placed as upon the belt as the cart is, there is no KE because there is no acceleration. The only 'drag' is that of friction of the wheels to the belt, and internal to the machine. The motor will idle to keep the process ticking over, and so keep the car in place on the belt.

Please include video evidence with the appropriate documentation.

I leave videos of the impossible to others.

 

[Subduction Zone]

Oh humber, you gave me so much hope on this last thread, all of the OK's until you blew it. If I find a link on Newtonian transforms will you try to understand it?

 

[humber]

I think you dropped a comma after the word "energy", but in any case I need to clarify that point. The value of the kinetic energy associated with some particular object in one frame is not necessarily the same in another frame (because the velocity may also be measured as being different). However, if we're looking at an isolated system then total energy is conserved. Is that what you meant? Force, mass, and acceleration are identical in two inertial reference frames (and friction also).

Yes, a missing comma. The same KE may be seen differently from each frame because of the relative velocities. The "connections" between each end every frame remain intact, 24/7.

I don't understand why you say the treadmill "fails quite obviously for all intermediate values". I was a bit lax in only talking about a cart on the treadmill while also at rest w.r.t. treadmill body/ground. We can also have the cart moving backwards at the same speed as the belt (as if it was at rest on "real ground" with a tailwind blowing past) and at any other speed also.

That last condition is the only correct case, and only if there is no motion of the cart wrt the belt.

Of course, we might need to have a longer treadmill in that case to ensure we have enough time to observe its behaviour before it possibly runs off one end of the belt or the other. But (hypothetically) we can make that treadmill longer and longer, in fact let's save some time and let it go all the way around the world. (At this point I'll refer you back my post #2744 in the original thread which I understand you are still working on replying to!)

On that last point. I found that example a bit contradictory. I did try to answer it, but came up with so many options, that I thought it more confusing. I have none of the quibbles that you mentioned, but the "holding with the hand" is a problem. That's one of the figurative ideas that I see in the treadmill. If you don't mind, I would rather stick with the treadmill. It saves "transferring" the models. Sometimes I wonder. Motor boats are now the same as passive floating objects...
The length of the belt is not the issue. It makes no difference to my criticisms.

In my not so humber opinion the treadmill with belt moving at say, 10 mph, and with the mass of surrounding air at rest w.r.t to the treadmill body is equivalent to a "real wind" of 10 mph flowing over a patch of ground (let's say also covered with treadmill belt material). You can now add the cart at whatever speed you wish (relative to the belt/ground) and the two systems are still equivalent.

No. That is not right. I will have to let that one go by for now.

I don't understand what you mean by "freeze it at standstill"? Can you elaborate please. Nor do I understand what "dynamic properties" are missing. Of course we do need to have the surface characteristics of the "real ground" and those of "treadmill" to be at least reasonably similar for the two to be more correctly interchangeable, but that also doesn't seem to be a major sticking point (no pun intended!)

In the real world the cart has real velocity w.r.t the ground. To observe it, you would need to physically move alongside it. Yet this scene is "captured" and brought back to a standstill w.r.t the ground. It is impossible to retain the behavior at windspeed in this manner.

When perturbed, a standard means of testing transient response, the treadmill cart has none of the characteristics of a 6oz vehicle traveling at perhaps 10mph. In wind, must be dynamically stable to keep on course. The treadmill cart is languorous and vague. That is because it is just skimming the belt, hovering. That is a critical difference. Not the cause, but an effect.
In combination with the cart itself, friction it is a major unsticking point.

Perhaps you can define "wind" or "real wind" for me so I know what you mean and why you say treadmill wind is not like a real wind. Sorry if I've missed this in some earlier post(s), but I still have no idea what you are getting at by making that distinction. I would have thought "wind" could reasonably well understood as air (usually) moving past the observer or some object (or some frame of reference) in a reasonably smooth and continuous flow? Here I mean "moving" as a relative thing, including the possibility of there being no relative motion (no wind). What makes one wind more "real" than another?

Yes, OK, but the difference is not of that kind.

I look forward to hearing more (although "today" in your preferred frame may be "tomorrow" in mine!)

Maybe for me too. A lot of posts to answer.

 

[humber]

Interesting dichotomy, when a boat is floating downstream it can never reach the speed of the water but when the boat is powered: . The humber universe never ceases to amaze me. humber a boat achieving the speed of the river it is drifting in is equivalent to a boat that is powered slowing down to nothing once the power is turned off.

In still water, a powered boat with its engine turned off, will the come to rest when it loses its KE to drag. A bit like a car under the same circumstances
But on the road. Friction and other losses equal drag. No canoes involved in either case, if that helps you.

If you can confuse one obvious statement of fact with a fantasy of your own, then I imagine that will not be a unique occurrence. Motor boats are not simple floating objects. That is the topic.

 

[humber]

That is equivalent to saying that a boat in still water will never coast to a stop once the power is cut. Again, the reference frame of the earth is not special. Look at the problem from the reference frame in which the water is not moving.

No, it does not imply that, Mender.
The reference frame of the Earth is not involved.
All motions mentioned are w.r.t the water itself. A motor boat can go as fast as engines and technology will allow. The topic is objects submersed or floating in water, driven only by that medium. Such objects will not reach the speed of that medium, in the way most would say "not travel as fast as the river".

 

[ThinAirDesigns]

And I suppose a hot air balloon in a steady breeze travels at some slower speed than the air -- likely because of drag.

JB

 

[humber]

And I suppose a hot air balloon in a steady breeze travels at some slower speed than the air -- likely because of drag.

JB

Hot air seems appropriate. Hot air balloons raise their potential energy in the gravitational field by gaining altitude. This energy can be used to gain velocity, leading some to think that the balloon is traveling faster than the wind.
I should add that boats are not balloons, but that is probably too much information for one sitting.

 

[spork]

I disagree spork, where humber is often unintentionally humorous I find humb to be constantly humorous. He is sort of a humber reductio ad absurdum. He is close enough to humber in style so that he seems to irritate him to no end.

True. I thought "I can't wait for them to split the threads". I never figured I'd spend 5 minutes on the dark side, but I was wrong. I've now become fully sucked into this hillarious sideshow!

I think that you may be right. I think I would have abandoned this thread if not for the comic relief of humb. Humber may be educated, but like you I have serious doubts about this.

1) Humb is in fact friggin' hillarious - but it worries me a bit that he's capable of the sort of "thought process" he's demonstrated. He's like some sort of savant.
2) I suspect humber actually is educated. But I also think it was probably the biggest waste of an education there ever was. He clearly knows some words. He simply can't put them together into sentences that have any objective meaning in a non-humberian universe. True they occassional fall together in such a pattern as to entertain me, but I liken that to a room full of monkeys attempting to type out the full text of Hamlet.

And you are easily distracted. You take a lot of time making derisive comments about other posts instead of addressing the topic.

I have nothing to add. But I fully approve this message!

Prof. Pratt's reply: "It's exactly the same". So there's your academic.

For what it's worth JJ, any one of us could provide humber a wheelbarrow full of academics to counter his silliness. But we don't do so because most of us aren't acquainted with an academic that's pissed us off bad enough to warrant disclosing their identity to humber... I'm just sayin'

I'm really intrigued by your description of what happens when an object is immersed in a moving river. Are you really saying that the water is providing a propulsive force, and simultaneously providing a drag force in the other direction? Which would be truly remarkable, since it would imply that the object is moving in both directions at the same time.

And this strikes you as something that wouldn't happen every day in the humberverse?

Oh humber, you gave me so much hope on this last thread, all of the OK's until you blew it. If I find a link on Newtonian transforms will you try to understand it?

SZ, you're starting to give humb a run for his money as funniest guy on this thread.

 

[mender]

No. The telemetry will not confirm that. You need to check the motor's consumption. A car in wind will consume more than the car on the belt.
In the wind, you will see the motor consume energy as it accelerates the car's mass (KE) and loses it to the forces of drag. Both will increase as long as the car is accelerating. If you stop accelerating at windspeed, then the load will be drag (all frictional losses) only. This will require a constant demand from the motor in order to keep it at that speed, and will also be at a maximum.

But the car did stop accelerating at wind speed in the outside test. It was traveling over the ground at the same speed and in the same direction as the wind; 10 mph in both cases, confirmed by the anemometer reading of zero. The amount of power needed from the motor will be quite small as there is no drag from the air; only the frictional drag. The power needed to maintain the speed will be a small fraction of the amount used to accelerate the car to that speed. It will not be at a maximum.

The car outside on the ground running at 10 mph in the 10 mph tailwind, and the car at 10 mph on the treadmill in still air will consume exactly the same power. How can there be a difference? Same aero drag, same frictional drag, no acceleration. And don't say the KE is different, because the KE is constant in both cases and will not change the power requirement.

The belt "gives" against the drive wheels. It is effectively on a static dyno, with a very small load. It is not likely to be stable, and could go either way.

If the car is placed as upon the belt as the cart is, there is no KE because there is no acceleration. The only 'drag' is that of friction of the wheels to the belt, and internal to the machine. The motor will idle to keep the process ticking over, and so keep the car in place on the belt.

Do you have a powered treadmill? That's what everyone is using for the tests and referring to when discussing the treadmill tests. It doesn't "give" against the drive wheels. It runs at a constant speed (adjustable) and resists changes to that speed. That's how it is able to keep a constant speed with a 200 lb human running or walking on it.

Maybe this is where the disconnect is.

 

[spacediver]

Observer A is on one of the flying masses. B is on the ground. Now you know that all views are equivalent, so they must agree. Yes, both say "relative to me" but they must also agree. How? The KE cannot appear or disappear with the viewer. It's energy, it cannot be destroyed.

So, how? If needed, ground observer B can use that energy to do work. But to do that work, say, to break a window, the object must lose velocity wrt to that observer. Right? It must decelerate to give up its KE.

I think this is a major conceptual sticking for humber.

I think he's worried that we violate the conservation of energy by allowing KE to be completely relative.

So what's wrong with the following analysis?

Let's conceptualize the available energy as a relational property rather than an intrinsic one.

A stick of dynamite has stored chemical energy, therefore it's ok to conceptualize it as intrinsic, or absolute.

But Kinetic energy is a different beast. The kinetic energy exists in a system of objects.

Suppose the universe consisted solely of spheres flying around in three dimensional space. Each of the spheres has its own mass, position, velocity.

So long as these spheres collide in a perfectly elastic manner, and so long as there is absolutely no friction of any kind, the total amount of kinetic energy should remain the same, no matter which frame of reference we analyze from.

Suppose there are three spheres in this universe: A, B, and C, each weighing 2 kg.

Let's say that A is traveling at the same velocity as B, and C is traveling at 10 m/s with respect to A and B.

If we analyze with respect to A's reference, we get:

KE = 0.5*m*v*v

B: KE = 0.5*2*0*0 = 0 Newtons
C: KE = 0.5*2*10*10 = 100 Newtons

Total = 0 + 100 = 100 Newtons

If we analyze with respect to B's reference, we get:

A: KE = 0.5*2*0*0 = 0 Newtons
C: KE = 0.5*2*10*10 = 100 Newtons

Total = 0 + 100 = 100 Newtons

If we analyze with respect to C's reference, we get:

A: KE = 0.5*2*10*10 = 100 Newtons
B: KE = 0.5*2*10*10 = 100 Newtons

Total = 100 + 100 = 200 Newtons

So don't we have a paradox here? Why is there more kinetic energy in the system when we analyze from C's perspective?

I believe this is the question which we need to address in order to convince Humber that KE is a relative value.

Thing is, I don't know how to solve the paradox.

 

[Thabiguy]

I don't normally enter this discussion, but there is something that didn't get said recently:

The force available to drive the object falls as the force against it rises. While the object is accelerating, thos forces are not in balance. One is square law, so it starts off relatively benignly, being lower than the driving force, but then increases rapidly to swamp it. It cannot reach waterspeed. Not even if the driving force is constant with velocity.

Drag is the force that drives the paper boat which had been dropped into a flowing river. What other force do you think is accelerating the boat forward?

The object in the water accelerates. When u is low, the drag is low. As u increases, the drag increases until terminal velocity is reached.

Let me remind you that

u is the velocity of the object relative to the fluid it is immersed in

, which you have acknowledged twice.

When the paper boat is dropped into a flowing river, u is high initially, and decreases as the paper boat accelerates downstream.

 

[sol invictus]

What else?

For a third time, you acknowledge that u is the velocity of the object with respect to the fluid it's immersed in.

You also agreed that F_drag=c(u) u², with c(u)>0, and that F_drag is the only force acting.

Yes, but you said the only solution.

Tell us, humber - what other solution to F = c u²=0 is there other than u=0, given what you just agreed to? Or are you flipflopping yet again?

The one you give is is relative to the boat at waterspeed, but that would mean the drag is zero at waterspeed. That's impossible.

humber, you just agreed that F_drag=c(u) u², with c>0, and that u is the velocity of the object with respect to the fluid it's immersed in. That means at waterspeed, which is u=0, F_drag=0. Even you should be capable of inserting u=0 into that equation.

So please, enlighten us - what have you flipflopped on this time?

I'm not going to bother with the rest of the garbage in your post - this is as clear as it gets.

 

[Clive]

So don't we have a paradox here? Why is there more kinetic energy in the system when we analyze from C's perspective?

Happy New Year (in my frame of reference).

The only paradox comes from someone (incorrectly) expecting the total kinetic energy of some system to be identical across different frames. I probably would have made this same mistake myself not so long ago, but as a result of spending lots of time on this thread and it's parent have learned (or possibly relearned) that way of thinking is wrong.

It's pretty "obvious" when you think about it, but perhaps because of the way most of the material is presented at high school level (as I vaguely recall, often using the ground as the frame of reference, and hardly ever looking at the same system using different frames), it's possibly quite easy to fall into a pattern of thinking where you understand kinetic energy as some kind of intrinsic thing "in" the moving object when in fact it's not really quite like that. All you have to do is look at the formula to see that the value is proportional to the square of the speed (velocity) and that clearly can change (and in a non-linear way) with different frames.

So in your example, if our frame of reference is moving at the same velocity as A or B, then C is the only object with non-zero velocity and therefore also the only thing "with" non-zero kinetic energy. When your frame puts C at rest, then we have both A and B moving at the same speed, meaning twice as much mass and so twice as much kinetic energy (in total). You could have more objects and/or different masses and relative velocities and get values that differed by as much as you liked when you used different frames of reference.

I'm not sure how it's described elsewhere, but I find (now) the best way to think of kinetic energy is simply as an amount of work that a particular "mass" is able to do because of it's motion relative to that frame. It's almost just a bookkeeping type of thing. Start with an object at rest, and we say that has zero kinetic energy. Do some "work" on it so that it now has non-zero velocity, and (assuming no losses) all that "work" must be recorded as kinetic energy.

However, for any isolated system, and one particular inertial frame of reference we will still have conservation of energy, even though the actual total value can vary from frame to frame.

Hopefully I got that more or less right! Don't know how much it really helps clarify things though.

 

[John Freestone]

They do, assuming they are not slowed by friction with the ground, or anything else.

We do, it's called a hot air balloon.

Yea! The trick with googling for information is knowing what stupid words to put in the box. Looking for strict physics links, the idea humber is contesting is so obvious it is seldom written down. But I just put "hot air balloon wind speed travel" in and that's a little more useful. Here's one of the first page full of possible hits, humber: http://www.ashevillehotairballoons.com/FAQ2.htm

"Depending on the wind speed the balloon will travel five miles an hour if the wind speed is at five miles an hour and ten miles an hour if the wind speed is at ten miles an hour."
​

I make that two-nil, not even counting other people's links.

Of course, I was careful to state in my first reply that there are real-world limitations to such a pure physics proposition, and I see that you have already begun to rely on those as the source of your objections. The point was made weeks and weeks ago that theoretically we could say that an object's speed approaches that of the fluid as an inverse exponential curve, never actually reaching it, so if you want to take things to ridiculous extremes of pure mathematics, sure, you'd have a point, but we're talking about real world conditions, and in those we find that the object might get pushed a little faster by another slightly faster current, then return to the main one - so now it would slow towards the fluid's speed again. Even in an absolutely pure system, that exponential curve continues to get closer to its target, so we would still also be right given the no more bizarre requirement that we allow sufficient time to reach steady state (infinite). The fact remains that in a reasonably short time, you would not be able to measure any difference in velocity. You wanted real-world intuitive examples a while back - all you have to do is chuck a piece of paper (maybe one of your diagrams of the cart) off a bridge into a river.

The trouble is that you'll argue one way (pure maths) if that suits some other error, and the other way (real world conditions) if it suits your earlier error; basically all of these arguments are ones you bring up to support earlier errors. Virtually everything you say is wrong.

 

[sol invictus]

Hopefully I got that more or less right! Don't know how much it really helps clarify things though.

That's exactly right. When you change reference frames the values of many things change - velocities, obviously, but also the energies of the individual objects and the total energy. If you also rotate or translate, angles and positions will change too.

There's no problem with velocities changing, because the laws of physics only ever involve relative velocities, and those don't change. There's no problem with the energy changing, because it does so in just the right way to keep all the laws the same. In fact if it didn't change, of if it changed in a different way, there would be a preferred frame.

 

[John Freestone]

When they are equal, no more acceleration is possible. That happens below waterspeed.

Astounding. You're an object travelling in water, propelled only by the water, and you reach some speed different from the water. Now no acceleration is possible because the forces balance. UUUUhhhhhh? If there is a relative velocity between you and the water, there is DRAG - that is the ONLY force there is - which is why it CONTINUES TO ACCELERATE YOU FURTHER!

Forget the piece of paper with the diagram, jump in the river yourself.

ETA: or please tell me what is the opposing force that keeps an object below waterspeed, the force that there must be to balance the drag pushing it further towards waterspeed.

 

[John Freestone]

That is equivalent to saying that a boat in still water will never coast to a stop once the power is cut. Again, the reference frame of the earth is not special. Look at the problem from the reference frame in which the water is not moving.

Interesting dichotomy, when a boat is floating downstream it can never reach the speed of the water but when the boat is powered: . The humber universe never ceases to amaze me. humber a boat achieving the speed of the river it is drifting in is equivalent to a boat that is powered slowing down to nothing once the power is turned off.

Yep, we're back to the same problem with the cart again - the boat in stationary water with the engine cut he can understand as slowing to a stop, because it's KE is lost to the water through drag, but as soon as we're in a moving medium, his synapses seem to overload and there's no way it can reach waterspeed! He seems to feel that the moving object must have some endless inertial force, a kind of absolute drag. To continue to flow with the river, the river has to keep overcoming this mysterious force, so it will balance at less than waterspeed. It's quite amazing that anyone over the age of 6 thinks like this, and he's supposed to have invented kit for oil pipes or something!

This mystery force - it's like that frame dragging thing again. It's like the earth's gravitational force doesn't just act along the line joining bodies, it drags them. They can't move round the surface of a planet in a vacuum at constant speed without using energy. Inertia is never overcome, but is a property of a mass that provides a constant force. I'm getting the hang of humberphysics.

 

[John Freestone]

Hot air seems appropriate. Hot air balloons raise their potential energy in the gravitational field by gaining altitude. This energy can be used to gain velocity, leading some to think that the balloon is traveling faster than the wind.
I should add that boats are not balloons, but that is probably too much information for one sitting.

Something correct in one sitting would be quite a surprise. You don't understand why hot air balloons rise, or why they move laterally, which has nothing to do with using potential energy gained by rising. I have a strong suspicion they don't actually gain potential energy as they rise, but lose it, as they are simply floating in a denser medium, but I'm not sure and all of that is a complete and utter tangent to the issue at hand.

If anyone thinks they move faster than the air they're in, those people have not arrived on this forum and the question is not the same as your apparent assertion that they don't get to windspeed. If you can't see the relevant connection between hot air balloons getting to windspeed and the boat or other object reaching waterspeed, which I think you raised first, saying that they didn't, then you're even humber than I thought. But we're at that strange point again where yet another assertion of yours that is at odds with classical physics has been analysed to the point where we can no longer tell if you're extremely stupid or just lying.

It's happened with relative velocities (yet has just had to be pointed out again on this very page); it's happened with kinetic energy (which you still manage to say may be relative, but that has no practical relevance to anything); now it's happening with the most trivial problem of fluid mechanics that could possibly be constructed, a system in which there is only a single relevant force. It's no wonder you can't understand the equivalence of inertial frames.

 

[Modified]

Something correct in one sitting would be quite a surprise. You don't understand why hot air balloons rise, or why they move laterally, which has nothing to do with using potential energy gained by rising. I have a strong suspicion they don't actually gain potential energy as they rise,

I think humber was talking about gravitational potential energy, which he seems to think will somehow affect lateral movement.

 

[Molinaro]

The earth's gravity will keep the submerged object from moving at the speed of the water. As long as it is in the earth's gravitational field, it will be pulled not only down, but also back from whatever other direction it would go. The vector tilts in the appropriate direction relative to the True Frame in order to support the truths that humber and I know. If it were moving at "riverspeed", there would be no force to create your purported "KE = O". Your assertions otherwise are unsupported. Show me an academic or paper that refutes us. You cannot.

This is easily demonstrated. I could construct an apparatus from popsicle sticks, chewing gum, and tinfoil that would suffice and settle this once and for all. I will not, however, as there is no need, and I cannot spare any tinfoil. I need it all for my hat.

As someone who taught a college course in ship stability I would like to point out that you are talking nonsense.

Seeing Humber act as if KE were a conserved quantity is laughable.
Seeing Humb act as if things can't float locked in with the flow of the water is laughable.