Merged DDWFTTW in a “Real” Wind

[Llyricist]

Well like I told Bob, I have time on my hands. And I actually am pretty good at sorting out data.

And yeah, I am aware that there are many runs worth to sort out.

 

[A.T.]

...

Got it. You don't know the difference between speed and acceleration.

Ask him what the acceleration of a ball on the top of it's trajectory is, when it was thrown vertically upwards.

 

[Jack by the hedge]

Not quite. One mass is constant at 1m/s. The other accelerates from 0m/s to 2m/s over 1 second. Both have traveled 1m, and the average velocity is the same, but the final velocity is doubled.

I have highlighted the part which is absolutely, completely and utterly wrong.

If the hand pulls at a constant 1m/s then the reel follows at a constant 2m/s.

If the reel accelerates from 0 to 2m/s in 1 second then it is because the hand accelerated from 0 to 1m/s in the same second.

You are confusing yourself by overcomplicating the problem. Perhaps you should stop worrying about forces and acceleration and simply consider the geometry of the setup.

We can do the experiment and observe that the reel rolls smoothly after the hand without slipping, and the string remains in tension.

So we can assume in our simplified model that friction is sufficiently high that we can disregard slipping effects and the distance between the reel and hand at any moment is simply the remaining length of free string.

Now whatever distance the hand moves forward, the same amount of string is wound onto the reel and the reel rolls twice as far. Can you see that?

D_reel = 2 * D_hand

It follows that

D_reel/Dt = 2 * D_hand/Dt

So

V_reel = 2 * V_hand

And

V_reel/Dt = 2 * V_hand/Dt

So

A_reel = 2 * A_hand


So if the hand is not accelerating (A_hand = 0) then the reel is not accelerating either (A_reel = 0).

Do you see that?

Sorry if the above appears to be belabouring trivial maths, but it really does look as if you don't understand it when you say things like "One mass is constant at 1m/s. The other accelerates from 0m/s to 2m/s". You can't be talking about the same configuration.

 

[GlennB]

Ask him what the acceleration of a ball on the top of it's trajectory is, when it was thrown vertically upwards.

You'd have to double dog dare me, because I fear the answer.

 

[Jack by the hedge]

You'd have to double dog dare me, because I fear the answer.

I bet he can show you some maths, though, and maths never lies.

It's a bit like the Delphic oracle, in that regard; it'll always tell you the truth, but you still come to a sticky end because you either asked it the wrong question or you misunderstood its answer.

 

[ThinAirDesigns]

.Pretty condescending response, I'd say.

Nothing condescending about that particular responsive "no" -- you were just plain wrong.

Since you appear incapable of figuring it out on your own, I'll explain it to you -- I'm merely *spoofing* your own condescending position.

I like folks who go out and do things. I like people who want to build things and figure it out for themselves. We alway encouraged folks to put their own carts together and see for themselves.

Normally good on you -- but this is different since you have made all sorts of stupid and condescending claims about your 'scientific rigor' compared to ours(ROFLAO), etc.

For your own benefit, you're performing very loosely controlled cute little tests of things that have been done for near ever. As others here have pointed out, your getting closer to being able to repeat the explanations that were given early in the thread.

Get over yourself. It's a brainteaser.

JB

 

[ThinAirDesigns]

The 2007 is the first I'm aware of.

If you want to be aware of more, stop telling and start asking. There are plenty of people on this thread who know the history of the device cold.

JB

 

[humber]

No.

JB

Bauer did it first in ( 1965?) in the sense that it was at least recorded. It was always possible before then. Transient above WS performance in a changing wind.

 

[humber]

Pretty soon he'll figure out that a treadmill indoors is an ideal way to test and verify a ddwfttw machine. Then he can tell you how to do these tests and build a proper cart.

Fact: your premise is the linear addition of velocities.

The law of superposition applies to linear systems. So amenable to analysis, that many non-linear systems are approximated as being linear, to make use of the accompanying mathematical tools.
And they can be used to show the cart is not a GT of anything, but a cart balancing on a belt.

But, at an a-b-c level, we can say that the belt cancels out the forward linear motion of the cart, leaving only the angular.
Cartoons show that, where Wily Coyote, tries to run along, say, a series of logs, but they spin as he tries, and he goes nowhere. TM, same thing, but the wheel is like the log. Not in the least proof, but an outcome of trail and error, and nothing more.

 

[jduffy77]

Fact: your premise is the linear addition of velocities.

The law of superposition applies to linear systems. So amenable to analysis, that many non-linear systems are approximated as being linear, to make use of the accompanying mathematical tools.
And they can be used to show the cart is not a GT of anything, but a cart balancing on a belt.

But, at an a-b-c level, we can say that the belt cancels out the forward linear motion of the cart, leaving only the angular.
Cartoons show that, where Wily Coyote, tries to run along, say, a series of logs, but they spin as he tries, and he goes nowhere. TM, same thing, but the wheel is like the log. Not in the least proof, but an outcome of trail and error, and nothing more.

The sheer stupidity of this oft repeated silliness of Humber is truly mind numbing. Notwithstanding the fact that the whole post is gibberish his conclusion is always that the cart will stay in place assisted by its magic, completely frictionless bearings. The wind driven cart will accelerate up the belt. Even if Humber's cart were not imaginary, it still could not travel up the belt.

 

[ThinAirDesigns]

Bauer did it first in ( 1965?) in the sense that it was at least recorded.

Wow -- humber got something just about right.

As far as we know, Bauer was the first to attempt and succeed. He did not come up with the idea independently and the concept he executed goes back at least 20 years before him.

JB

 

[humber]

Ask him what the acceleration of a ball on the top of it's trajectory is, when it was thrown vertically upwards.

Little Johnny can read a highschool text book.
The KE at the top of the arc is zero, and the gravitational potential energy at maximum. Prove that, while assuming that there is a constant acceleration of g on the ball.
You are behind a car that is rolling towards you, so you push on it for sufficient time, such that it moves the other way. Write the questions for the time t0 just before it reverses, and t1 just after it reverses, and then justify "t"

 

[humber]

Wow -- humber got something just about right.

As far as we know, Bauer was the first to attempt and succeed. He did not come up with the idea independently and the concept he executed goes back at least 20 years before him.

JB

That does bring "one man's struggle against the wind" into the correct light.
Bauer achieved 40 seconds above WS from standstill - no pushing - and used a tell tale and estimated the windspeed. He had no instruments. His analysis is nothing like Spork's, ( Smith's) and is not a steady-state solution.

 

[Modified]

Little Johnny can read a highschool text book.
The KE at the top of the arc is zero, and the gravitational potential energy at maximum. Prove that, while assuming that there is a constant acceleration of g on the ball.

What are you saying here, that it's trivial (which it is), or that it's not true? Do you really think acceleration changes throughout the arc?

 

[spork]

Wow -- humber got something just about right.

As far as we know, Bauer was the first to attempt and succeed. He did not come up with the idea independently and the concept he executed goes back at least 20 years before him.

Yes, but I think you and I agree that he very likely did not exceed wind speed with his manned cart. His tell-tale was very low and directly in front of the prop. From his description, it sounds as if it only indicated that he went slightly faster than the wind - which we've learned is almost certainly slower than the wind when you account for wind gradient and the effects of the prop.

There is no doubt however that he would have succeeded if he'd realized this and continued to work on his cart. There's also no doubt that he did succeed with model carts on a homemade treadmill.

Finally, there is no doubt that he learned of the entire concept from a student paper he'd been given.

What are you saying here, that it's trivial (which it is), or that it's not true? Do you really think acceleration changes throughout the arc?

What he's trying NOT to say is that he believes the acceleration is zero at the instant it's at the top of the arc. He's argued that strenuously, but is now in the phase of trying to talk around it. He may eventually get to the phase in which he lectures us on how the acceleration is constant.

 

[I Ratant]

If you want to be aware of more, stop telling and start asking. There are plenty of people on this thread who know the history of the device cold.

JB

.
And must have their asses kissed to "reveal" the secret information.

And then only reluctantly, with snarky comments about the questioners.
Show what you- TAD- have done.

 

[I Ratant]

That does bring "one man's struggle against the wind" into the correct light.
Bauer achieved 40 seconds above WS from standstill - no pushing - and used a tell tale and estimated the windspeed. He had no instruments. His analysis is nothing like Spork's, ( Smith's) and is not a steady-state solution.

.
Didn't have to be.
It was apparently the first.
That's what would count in a record book.
Faster, longer, higher, just takes tossing lots of cash at the thing, as with everything.
The principle has promise, for what it could do.
Who was the next man to top Everest after Hillary and Norkay? Don't goggle.

 

[I Ratant]

Tacking prop?

 

[spork]

.
And must have their asses kissed to "reveal" the secret information.

And then only reluctantly, with snarky comments about the questioners.
Show what you- TAD- have done.

Still wrong. All anyone has to do is ask questions without BEING an ass. You've not yet tried that approach.

.
It was apparently the first.
That's what would count in a record book.

Wrong on both counts. It wasn't the first because it almost certainly didn't exceed wind speed. But what counts in the record books is PROVING that you accomplished the goal under their rules and their supervision. And if by some magic, Bauer's manned runs made it into the record books, our record would still stand. You'd actually have to bother to see what record we set of course.

 

[humber]

What are you saying here, that it's trivial (which it is), or that it's not true? Do you really think acceleration changes throughout the arc?

You tell me how it can't. There's more to the topic than what a simple text book says.
It's not wrong, but incomplete.