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Veritasium wrong about faster than wind direct down wind.

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sleemanj:

electrodacus:

--- Quote from: sleemanj on December 10, 2021, 11:57:30 pm ---

--- End quote ---

Yes I saw that video.

Steve is smart enough not so say anything about direct down wind.

PlainName:

--- Quote ---Big difference is that desk fan is not powered by that wind it creates.
--- End quote ---

You're skipping ahead. Clearly, the prop turns. Is it powered by the wind or wheels? Leave that for the moment and just consider that it's turning.

That is simple refutation that the air molecules are moving at the same speed as the prop. They are not. Once you realise that (actually, accept that because even after having pointed this out a few times it seems you still haven't), we can consider what causes the prop to turn.

Regarding the desk fan and taxiing airplane, we are talking vastly different leverage. In both of those the propeller is turning at massive speed, producing (or using) a lot of wind. With the FTTW vehicle it is orders of magnitude less. But that's not important, is it? The effect is either there or it is not - the scale of the effect is only meaningful when we consider what it can do, but before that we just want to agree that it exists.

electrodacus:

--- Quote from: dunkemhigh on December 11, 2021, 12:10:15 am ---
--- Quote ---Big difference is that desk fan is not powered by that wind it creates.
--- End quote ---

You're skipping ahead. Clearly, the prop turns. Is it powered by the wind or wheels? Leave that for the moment and just consider that it's turning.

That is simple refutation that the air molecules are moving at the same speed as the prop. They are not. Once you realise that (actually, accept that because even after having pointed this out a few times it seems you still haven't), we can consider what causes the prop to turn.

Regarding the desk fan and taxiing airplane, we are talking vastly different leverage. In both of those the propeller is turning at massive speed, producing (or using) a lot of wind. With the FTTW vehicle it is orders of magnitude less. But that's not important, is it? The effect is either there or it is not - the scale of the effect is only meaningful when we consider what it can do, but before that we just want to agree that it exists.

--- End quote ---

There is a stored pressure differential that powers the blackbird even before exceeding wind speed. That pressure differential is created by the propeller using wind energy while vehicle speed is well below wind speed.
The vehicle will continue to accelerate past wind speed as long as there is enough stored energy and will start to slow down when that is all used up.

Alex Eisenhut:

--- Quote from: electrodacus on December 10, 2021, 11:53:35 pm ---
--- Quote from: Alex Eisenhut on December 10, 2021, 11:50:27 pm ---
I was about to ask how a desk fan can make wind since the propeller is not moving relative to the desk?

Or for that matter, why does it take less time flying to Germany from Canada than the other way?

Or if you build a Veritasium vehicle but reverse the gearing so the prop blows forward.

Will it run slower than the wind or not?

--- End quote ---

Big difference is that desk fan is not powered by that wind it creates.  It has an external energy source.

--- End quote ---

Then what does the relative movement have to do with anything? The power source, as you state yourself, is the stored energy of the moving vehicle using some energy to spin the prop.

How fast would the vehicle move if the prop blew forward?

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