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

[mender]

I did read the entire page that you linked. This is at the bottom of the page:

"A force is not required to keep a moving book in motion; and a force is not required to keep a moving sled in motion; and a force is not required to keep any object horizontally moving object in motion."

However I didn't go to any of the other pages. Is the part that you want me to read on one of those?

Here's an excerpt from Lesson Two (I've scored 100% on all the exercises so far by the way):

"Forces only exist as a result of an interaction."

Yes, I have a powered treadmill and it goes all the way to 14 mph (well, the belt does, the treadmill just sits there). I've been refining my testing to give consistent results. Here's my first report:

"I received my cart yesterday and assembled it last night - good way to bring in the New Year!

I ordered a variety of parts with my cart to do some extended testing - extra wheels and props to check various advance ratios and such.

In the following list, the break-even speed is followed by the prop diameter and pitch. Here are the initial results:

6.2 mph with 15x7.5
6.8 mph with 12x8
7.2 mph with 12x6
8.8 mph with 12x3.8
9.3 mph with 10x8 with 4 blades

My cart is still breaking in as it runs, so hopefully with a little tuning and some more running time the cart will get more efficient."

I do have a fan and have mounted a propeller on an electric drill for some of my own testing. I don't have a way of posting videos, but I promise to tell you exactly what my results are no matter what happens.

 

[humber]

To try and make some progress (and attempt to stop the building level of insults being bounced back and forth), I'm going to start something different. For each apparent error we can create a single post with a title that describes the error and in the body quote the part of the post that includes the error followed by definitions and links to help resolve the error. Please try to provide links and the text of what the link provides.​

Good idea Dan_O, thanks.

While velocity is indeed a vector and velocity can vary over time, the statement appears to say that a vector is a time variant quantity. A better choice of wording and structure may have avoided the confusion.

A problem is that almost everything is open to interpretation, including Wikki and meteorological balloons. Perhaps there should also be a list of claims that are withheld or denied, and those which are trivial and should be ignored. I have several times stated that the flywheel applied only to Ynot's setup, and that the wheels spinning is neither here no there. Sometimes it may, sometimes not, but it is unimportant.

The vector matter is not easily cleared up by defining a vector. The translation from windpseed is made solely on one value, (Beltspeed) yet the intermediary values, all the way to say to zero speed, are assumed to be correct. They are not. The claim where it holds at all, it is not for windspeed, but going back with the belt. Windspeed is based upon one singular invalid case. How do you Wikki that, or get agreement when so many other errors in this thread support the contrary conclusion?

 

[humber]

I did read the entire page that you linked. This is at the bottom of the page:

"A force is not required to keep a moving book in motion; and a force is not required to keep a moving sled in motion; and a force is not required to keep any object horizontally moving object in motion."

Kinematically yes. Not in reality. And the freefall example, where the forces of drag and gravity are opposing? Not only opposing but dependent on each other?
If you remove gravity, won't the drag stop? This is an interdependent situation. So does a force that opposes itself, end up not being a force, just when split equally into gravity and drag? Gravity does work to make the drag.
The book on your table does not move, yet the force from the table opposes the force of gravity, so as to be zero. Force or no force?

However I didn't go to any of the other pages. Is the part that you want me to read on one of those?

Here's an excerpt from Lesson Two (I've scored 100% on all the exercises so far by the way):

"Forces only exist as a result of an interaction."

Yes, which is why zero KE is a meaningless solution.

Yes, I have a powered treadmill and it goes all the way to 14 mph (well, the belt does, the treadmill just sits there). I've been refining my testing to give consistent results. Here's my first report:

"I received my cart yesterday and assembled it last night - good way to bring in the New Year!

I ordered a variety of parts with my cart to do some extended testing - extra wheels and props to check various advance ratios and such.

In the following list, the break-even speed is followed by the prop diameter and pitch. Here are the initial results:

6.2 mph with 15x7.5
6.8 mph with 12x8
7.2 mph with 12x6
8.8 mph with 12x3.8
9.3 mph with 10x8 with 4 blades

My cart is still breaking in as it runs, so hopefully with a little tuning and some more running time the cart will get more efficient."

I do have a fan and have mounted a propeller on an electric drill for some of my own testing. I don't have a way of posting videos, but I promise to tell you exactly what my results are no matter what happens.

Good, thanks.

 

[mender]

Humber, your claims about the cart and the treadmill have wandered down so many side roads, maybe it is time to restate clearly, in point form, what you object to with regards to the DDWFTTW cart and the treadmill test results.

 

[spacediver]

Yes, that is zero net force, zero differential force. The forces are still there. When a body is dragged through a fluid by an external force, say a sphere through oil, the drag opposing that motion rises with velocity.

Correct.

When those opposing forces are equal, acceleration stops, and that velocity is the maximum that is available for that applied force.

Yes, because the air resistance is equal in magnitude to the downwind force.

Drag and applied forces are not independent forces, but drag is the reaction to the applied force. So, that applied force is there, sustaining the velocity, acceleration or not.

The air resistance (I'm using this term instead of drag since I think drag has a more complex meaning), is a reaction to the object colliding with air particles. At terminal velocity, the air resistance is at a maximum. I think we agree here.

That is what I know you think, and why, but it is wrong.
As the velocity rises, the drag increases, not linearly, but at least the square of that velocity.

Air resistance increases as the velocity of the object increases. Whether its linear or not is not is beyond my level of understanding.

Now you can see that if applied force is truly constant, ( it is not itself dependent upon velocity) then the object's velocity will rise until the drag equals and opposes that fixed (constant) force.

No. The applied force is not constant. The applied force is a function of the relative velocities of the object and the downwind particles. The applied force reaches a minimum at terminal velocity, since the velocity of the object has almost caught up to the speed of the wind. This is where you keep getting hung up.

Remember, force is not a property inherent in an object, it is a measure of an interaction between two objects.

Imagine a glass sphere is flying through space at 10 m/s relative to a stationary observer. Then someone throws a hard rock from behind the sphere, aimed at the sphere. The rock is thrown at 100 m/s.

The difference in velocities is 90 m/s.

Now suppose we rewound time, but now the glass sphere is moving at 80 m/s and the rock is thrown at 100 m/s.

The difference now is 20 m/s.

In which scenario is the glass sphere more likely to be cracked, when the rock catches up to the sphere?

The answer is the first scenario, even though the rock had the same velocity relative to the stationary observer.

So in the object accelerating due to wind, the highest applied force will be right at the start, when the object begins to accelerate.

 

[mender]

Kinematically yes. Not in reality. And the freefall example, where the forces of drag and gravity are opposing? Not only opposing but dependent on each other?
If you remove gravity, won't the drag stop? This is an interdependent situation.

No, not interdependent. If you remove the drag does the gravity disappear?

If you remove gravity, won't the drag stop? This is an interdependent situation.

The drag doesn't disappear until the difference in velocity between the object and the air is zero. The drag is dependent on that difference, not gravity.

When the force of gravity is balanced by the force of the drag, the object ceases to accelerate. When one is removed (drag or gravity), the object accelerates again until the forces acting on the object are balanced again.

The book on your table does not move, yet the force from the table opposes the force of gravity, so as to be zero. Force or no force?

Once again, the forces are balanced, so there is no acceleration. It acts exactly the same way as an object with no forces acting on, and also the same as one with a million times more force.

How did you score on your link?

 

[humber]

Humber, your claims about the cart and the treadmill have wandered down so many side roads, maybe it is time to restate clearly, in point form, what you object to with regards to the DDWFTTW cart and the treadmill test results.

Well Mender, I have done that. The side roads are not of my making. Sometimes I will use a different approach to try and restate what I think is already made.
It is difficult to get agreement if one side is willing to believe that say, the laws of physics can be broken, nor accept that lack of evidence, or flawed evidence as in the case of windspeed object, is a serious blow to the claim that there are such objects. I cannot think of one argument of mine against the treadmill, that has been denied. Ignored or recanted, certainly, but never accepted as being correct.

The equal forces at terminal velocity is interesting. I do not see the world in the way you do, as velocites. For a number of reasons, I look where the energy goes, where the information is. What informs what?

I think that you will agree that an object in gravitational free fall in a vacuum, will accelerate? You see its velocity increasing. "Ah, F=ma, so there must be force", perhaps?

What difference does air make? The object no longer accelerates a terminal velocity, so from the previous reasoning, no force.
But what if you used an infra-red camera? Friction heats the body and raises its temperature. That means work is being done, and you see that, and conclude that there must be force.
The lack of friction in a vacuum would lead you to conclude that there was no force.
Sometimes you do see the cause, and other times, only the effect.

 

[CORed]

Keep digging. Simple one for you. Name a body the travels at a fixed veloicty w.r.t the ground that does not have force upon it. You failed to do that for the KE question.

A hot air balloon, drifting with the wind.

 

[mender]

What difference does air make? The object no longer accelerates a terminal velocity, so from the previous reasoning, no force.

No, no, no! I already said, the forces involved can be zero or a million times as much but they are balanced, which is the same as saying no unbalanced force. There can also be a million different forces that cancel each other out and the result is still zero acceleration, because there is no unbalanced force acting on the object.

There is a huge difference, and you have to stop exchanging the phrase "no force" for "no unbalanced force". You can't do that and expect to understand what is going on.

Measuring an increase in temperature of an object would tell me that it is absorbing energy. It tells me nothing about any forces, balanced or otherwise.

 

[Modified]

Same drag, same density. It's hypothetical. The point being why should you make a distinction between this and an canoe or other object? If the water has force driving it at waterspeed, why not upon a real object?

A force is only necessary to accelerate it to that speed. Once at that speed, if the boundary (air and riverbed) were perfectly friction-free, and the river perfectly uniform and level, then no force would be needed to maintain that speed.

In a real river, something unpowered that is not in contact with the banks or surface (or is in contact with the surface if the air is at the same speed as the water) and is not at water speed will reach water speed. It will do that, in the end, by changing the speed of a huge volume of water by a negligible amount.

 

[69dodge]

Yes, the wind continues to exert a force at terminal velocity, but this is balanced by the force due to air resistance. So the forces cancel out, resulting in zero net force on the object, which is why it remains at a constant velocity.

Are you talking about something like a balloon that's floating along in a wind, at the same speed as the wind?

In that case, I don't think the balloon experiences any forces from the wind or from air resistance, not even balanced forces (well, besides the usual atmospheric pressure, anyway). The wind behind the balloon doesn't need to push it through the air in front of it, because the air in front of it is also moving forward as part of the wind.

A pair of balanced forces is the same as no force, insofar as both result in no acceleration. But they aren't the same in all respects. For example, the balloon would get squashed a bit if opposing forces were applied to opposite sides of it, but not if no forces at all were applied to it.

 

[spacediver]

Are you talking about something like a balloon that's floating along in a wind, at the same speed as the wind?

In that case, I don't think the balloon experiences any forces from the wind or from air resistance, not even balanced forces (well, besides the usual atmospheric pressure, anyway). The wind behind the balloon doesn't need to push it through the air in front of it, because the air in front of it is also moving forward as part of the wind.

ah didn't think about this, although you could argue that there will be a tiny bit of air resistance since the balloon itself will be blocking a tiny volume of space ahead of it from wind influence.

 

[Brian-M]

I'm almost certain this is humber posting under another name. I refuse to believe anyone else is capable of this .... whatever this is.

No... there's a clear difference. Humber's nonsense is scarily earnest, while Humb's nonsense is idiotically facetious.

 

[Dan O.]

Re: humber#1: terminology - is it "vector" or "variable"

The vector matter is not easily cleared up by defining a vector.

I'm really trying to help you humber. But you completely failed to address the issue. What did you mean by "Velocity is a vector. A time-variant quantity." ?!

Are you saying that you believe vector means a time-variant quantity or was that just a poorly structured statement??

 

[ynot]

Air (winds) and water (rivers) are not solid objects that travel at a single speed.

 

[Brian-M]

Hot air balloons have an engine. A heat engine. Shut up.

A heater, not a heat-engine. The heater is to lower the density of the air inside the balloon so that it's average density is less than the colder air outside it.

I suppose, if you made a hot air balloon asymetrical, you could use ascending/descending motion of the balloon (caused by heating the internal air and allowing it to cool a little) to push the air its displacing with a greater force in one direction, adding slightly to the balloon's velocity.

That's about the only practical way I can think of that it's potential energy could be used to increase the velocity of a hot-air balloon, but as hot air balloons are generally symmetrical, its a moot point.

 

[Modified]

ah didn't think about this, although you could argue that there will be a tiny bit of air resistance since the balloon itself will be blocking a tiny volume of space ahead of it from wind influence.

Once at wind speed, the balloon is just part of the wind (assuming a uniform wind from top to bottom).

 

[Modified]

Air (winds) and water (rivers) are not solid objects that travel at a single speed.

Nobody said they were.

 

[Brian-M]

Tracking balloons are used to follow the wind, to have short enough acceleration times to follow the changes. They travel at the mean speed of the wind, not the peak (maximum) speed of the wind.
It's even in the text.

Ummm... Mean wind speed is "wind speed"... but you're arguing that balloons don't travel at wind speed because they only travel at mean wind speed? You're not making any sense.

Wind is a moving mass, and when at windspeed, the balloon becomes essentially part of it. How do you get to windspeed in this manner?

If the baloon has become part of the moving mass of the wind because it is travelling at windspeed, then it is already at wind speed, and there is no need for it to do anything to get to windspeed, because it's already there. Do you even think about what you're typing?

Be more like the air, like a balloon, but even they can't quite do it. The drag is never quite zero, so 100% windspeed is not possible.

The drag is accelerating the balloon, pulling it in the same direction as the wind. The only point at which drag is zero is at windspeed. A free-floating balloon that won't achieve 100% windspeed is not possible.


Possibly the fluid nature of wind/water is confusing you, so let's use a more solid example.

Think of a river (or the wind) as a treadmill. Placing a floating object on a river (on in the wind) is similar to placing an object on a treadmill.

If you place a ball on a treadmill the friction (ie. "drag) of the treadmill will accelerate the ball. It will take time for the "drag" of the belt to get the ball up to belt-speed, but if the treadmill is long enough, it will eventually get there.

Claiming that unpowered boats cannot reach river-speed, or balloons cannot reach wind-speed, is pretty much the same thing as saying that objects placed on a treadmill can never reach the same speed as the belt. It just makes you look like an idiot.

 

[spork]

I'm thinking we need one of these Star Trek geek types to chart the full humberverse and humberian physics. Then they can write "humber for dummies" and it'll give us a fighting chance of unraveling this mystery. But "humber for dummies" is just a guide-book so to speak. It's not the full manual and teachings that would keep you safe in the humberverse. Without developing the zen-like ability to change your mind even faster than you type you wouldn't stand a chance on your own in the humberverse. Even "humber for dummies" would never be a printable book. It would have to be posted on a dedicated website so that it can be continuously updated even as we read it.

I strongly discourage anyone from entering the humberverse without a spotter that has at least one foot in the real universe at all times.

I've got the most unsettling feeling that in the humberverse extra socks appear in the dryer without explanation. I guess I'll just wait for the book.