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Physicists Called this Impossible


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  • Administrator
Salty Dog

If you want more detail on the explanation here it is:
1. The car is powered only by the wind. There is no motor or batteries of any kind.
2. The propeller does NOT spin like a windmill. The wind does NOT push it and make it turn.
3. Instead the wheels are geared to the propeller to turn it the opposite way, like a fan, so it pushes air backwards.
4. To start the vehicle the wind simply pushes on the whole vehicle (like a block of styrofoam) and gets it moving.
5. The wheels are turning so they turn the propeller in the opposite direction to how the wind is pushing it.
6. The prop is pushing air back so air pushes the prop forwards, accelerating the car.
7. Once you get up to wind speed there is no apparent wind on the vehicle. If the prop were spun like a windmill this would mean no more thrust. But, since the prop is operating like a fan, it still accelerates air backwards, generating thrust.
8. You can go faster than wind speed continuously because even when going faster than the wind, the prop can still accelerate air backwards (in the car's frame of reference) generating thrust. In a stationary frame of reference you would see that the wind behind the propellor is slower than the surrounding air. So it's clear that the energy is coming from the wind.

FAQ: If power is coming from the wheels to turn the prop, why doesn't that slow down the wheels more than it gets the prop to push back?
A: Because the wheels are moving over the ground much faster than the prop is moving through the air (because there's a tailwind).

Example: 
Let's say the car is going 12m/s in a 10m/s tailwind, so faster than the wind (note the prop will be moving through an apparent headwind of 2m/s).

Power = Force x Velocity

Let's say the chain applies a drag force of 100N on the wheels to drive the prop. This means we're taking power from the wheels = FxV = 100N x 12m/s = 1200W

If we apply this power to the fan, it can create a force of F = P/V = 1200W / 2m/s = 600N

Admittedly I've assumed no losses, but even if we waste half the power, we'd still get 300N of thrust which is more than the 100N of drag the prop adds to the wheels. The key is that we're harvesting power at higher speed, lower force, and deploying it at lower speed, higher force (which is only possible because we have a tailwind - in still air this wouldn't work because the relative velocity of the wheels over the ground would be exactly the same as the relative velocity of the prop through the air).

 

Even some physics professors say this craft breaks the laws of physics. This video is sponsored by Kiwico, For 50% off your first month of any subscription crate from KiwiCo (available in 40 countries!) head to https://www.kiwico.com/Veritasium50

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A HUGE thanks to Rick and Neil for letting me drive Blackbird. Check out Rick's YouTube Channel for more in depth videos and explanations on going faster than the wind downwind -- https://ve42.co/Rick

Gene Nagata made the shoot possible. If you’re a video nerd like me, check out his channel, Potato Jet: https://www.youtube.com/c/PotatoJet/f....

Xyla Foxlin for made the model cart used in this video. Xyla builds amazing things like rockets and canoes, check it out! https://www.youtube.com/c/xylafoxlin/

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References
Jack Goodman's YouTube video -- https://ve42.co/Goodman
Rick's treadmill footage -- https://ve42.co/Treadmill
Rick's multiple explanations of how Blackbird works -- https://ve42.co/DDWFTTW
Forum discussions -- https://ve42.co/forum Blog -- https://ve42.co/blog1 and retraction https://ve42.co/BlogRetraction

Gaunaa, M., Øye, S., & Mikkelsen, R. F. (2009). Theory and design of flow driven vehicles using rotors for energy conversion. In EWEC 2009 Proceedings online EWEC  

Md. Sadak Ali Khan, Syed Ali Sufiyan, Jibu Thomas George, Md. Nizamuddin Ahmed. Analysis of Down-Wind Propeller Vehicle. International Journal of Scientific and Research Publications, 3, 4. (April 2013) ISSN 2250-3153. (www.ijsrp.org)

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Special thanks to Patreon supporters: Bill Linder, Paul Peijzel, Crated Comments, Anna, Mac Malkawi, Michael Schneider, Oleksii Leonov, Jim Osmun, Tyson McDowell, Ludovic Robillard, Jim buckmaster, fanime96, Juan Benet, Ruslan Khroma, Robert Blum, Richard Sundvall, Lee Redden, Vincent, Marinus Kuivenhoven, Alfred Wallace, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Pindex, Michael Krugman, Cy 'kkm' K'Nelson, Sam Lutfi, Ron Neal

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Thanks to James Lincoln for building the initial prototypes for a model blackbird.

Written by Derek Muller, James Lincoln, and Petr Lebedev
Animation by Mike Radjabov and Iván Tello
Filmed by Gene Nagata, Derek Muller, Trenton Oliver, AJ Fillo and Emily Zhang
Edited by Trenton Oliver 
Music from Epidemic Sound https://epidemicsound.com
Additional video supplied by Getty Images 
Produced by AJ Fillo

 

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  • Administrator
Salty Dog

 

A UCLA Physics Professor bet me $10,000 that my video about going downwind faster than the wind was wrong. This video is sponsored by Brilliant. The first 200 people to sign up via https://brilliant.org/veritasium get 20% off a yearly subscription. 

For more information about the Veritasium Science Communication Contest check out -- https://ve42.co/contest

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The wager agreement: https://ve42.co/wager

Prof. Kusenko's slides: https://ve42.co/Kusenko

My rebuttal: https://ve42.co/rebuttal
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Huge thanks to Xyla Foxlin for building the model cart, and making the instructions so accessible to the public. Check out Xyla's video -- https://youtu.be/VUgajGv4Aok

A massive thanks to Bill Nye, Neil DeGrasse Tyson, and Sean Carroll for witnessing the signing of the wager.

A huge thanks to Prof. Alexander Kusenko for being a man of honour -- it's a difficult thing to change your mind, especially in a public forum.

A huge thanks to Prof. Mark Drela for the interview and help making sure we got the physics right.

A massive thanks to Rick Cavallaro for making Blackbird, all your insights, analysis, data, and general help with these videos -- it was so fun to work with you on this crazy project -- check out Rick's channel https://ve42.co/Rick

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References
M. Drela. Dead-Downwind Faster Than The Wind (DDWFTTW)
Analysis (Jan 2009) -- https://ve42.co/Drela

2013 AAPT United States Physics Olympiad Semifinal Exam -- https://ve42.co/AAPT2013

Rick's treadmill footage -- https://ve42.co/Treadmill

Rick's multiple explanations of how Blackbird works -- https://ve42.co/DDWFTTW

Blackford, B. L. (1978). The physics of a push‐me pull‐you boat. American Journal of Physics, 46(10), 1004-1006. — https://ve42.co/Blackford1979

Ruina corrects errors in the above paper: http://ruina.tam.cornell.edu/research...

Forum discussions -- https://ve42.co/forum Blog -- https://ve42.co/blog1 and retraction https://ve42.co/BlogRetraction

Bauer, A. B. (1969, April). Faster than the Wind. In First AIAA Symposium on Sailing. -- https://ve42.co/Bauer1969

Bauer's Obituary -- https://ve42.co/BauerObituary

Gaunaa, M., Øye, S., & Mikkelsen, R. F. (2009). Theory and design of flow driven vehicles using rotors for energy conversion. In EWEC 2009 Proceedings online EWEC  

Md. Sadak Ali Khan, Syed Ali Sufiyan, Jibu Thomas George, Md. Nizamuddin Ahmed. Analysis of Down-Wind Propeller Vehicle. International Journal of Scientific and Research Publications, 3, 4. (April 2013) ISSN 2250-3153.


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Special thanks to Patreon supporters: Mike Tung, Evgeny Skvortsov, Meekay, Ismail Öncü Usta, Bill Linder, Paul Peijzel, Crated Comments, Anna, Mac Malkawi, Michael Schneider, Oleksii Leonov, Jim Osmun, Tyson McDowell, Ludovic Robillard, Jim Buckmaster, fanime96, Juan Benet, Ruslan Khroma, Robert Blum, Richard Sundvall, Lee Redden, Vincent, Marinus Kuivenhoven, Alfred Wallace, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Pindex, Michael Krugman, Cy 'kkm' K'Nelson, Sam Lutfi, Ron Neal

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Written and Edited by Derek Muller
Animation by Mike Radjabov
Manim equations by Jonny Hyman
Filmed by Emily Zhang and Raquel Nuno
Music from Epidemic Sound https://epidemicsound.com and by Jonny Hyman
Additional video supplied by Getty Images
Produced by Emily Zhang, Petr Lebedev and Derek Muller
 

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  • Administrator
Salty Dog

 

Check out KiwiCo and get 50% off your first month of ANY crate at https://www.kiwico.com/xylafoxlin

💸 Support me on Patreon: 
https://patreon.com/xylafoxlin

Derek's First Video on Blackbird: https://youtu.be/jyQwgBAaBag
Derek's Second Video: https://youtu.be/yCsgoLc_fzI

A HUGE thank you to my friend Shane for stepping in and helping me with overnight CAD while I was overwhelmed and struggling and seriously needed to just sleep. Y'all should give him a follow, he is a very cool rocket kid! https://twitter.com/Shanepc14

Follow me on social media:
📸 Instagram: https://www.instagram.com/xylafoxlin/
🐦 Twitter: https://twitter.com/xylafoxlin
📘 https://www.facebook.com/xylareifoxlin

💌SEND ME THINGS📦:
Xyla Foxlin
10866 Washington Blvd. # 610
Culver City, CA 90232 

Build your own Impossible Wind Cart: 
------------------------------------------------------------
**I HIGHLY recommend ordering ordering extra parts, especially ball bearings and plastic gears. The listed quantities are what is on the cart in it's final form.**

CAD Files: https://www.thingiverse.com/thing:489...

My 3D Printer (Creality CR-200B): https://www.creality3dofficial.com/pr...

Bill of Materials from McMaster-Carr:
https://www.mcmaster.com/
1x 12205T79 Natural Rubber Bands Size 73, 3/8" Wide x 3" Long
6x 60355K42 Ball Bearing Shielded, Trade No. R3-2Z, for 3/16" Shaft Diameter
2x 7297K12 Plastic Miter Gear 48 Pitch, 24 Teeth
2x 1263K55 Rotary Shaft 316 Stainless Steel, 3/16" Diameter, 24" Long
2x 8978K113 Rigid Aluminum Tubing 3/16" OD, 0.022" Wall Thickness, 490 PSI Maximum Pressure, 3' Long
2x 6432K19 Set Screw Shaft Collar for 3/16" Diameter, Zinc-Plated 1215 Carbon Steel

The Propeller: https://www.apcprop.com/product/14x4-...
(affiliate link, not the prop I used: https://amzn.to/3y58jz0)

Pretty Purple Filament: https://amzn.to/3A8cXOJ ;)

Alternatively, a good friend of mine wanted to build this and shaved $14 off the BOM still ordering from McMaster. I can't vouch since it's not what I built specifically but I'm fairly certain it'll be exactly the same:
1    1    Pack of 360    12205T79    Natural Rubber Bands Size 73, 3/8" Wide x 3" Long
2    2    Each    7297K12    Plastic Miter Gear 48 Pitch, 24 Teeth
3    2    Each    8978K113    Rigid Aluminum Tubing 3/16" OD, 0.022" Wall Thickness, 490 PSI Maximum Pressure, 3' Long
4    2    Each    6432K19    Set Screw Shaft Collar for 3/16" Diameter, Zinc-Plated 1215 Carbon Steel
5    6    Each    57155K374    Stainless Steel Ball Bearing Precision, Shielded, NO. R3-2Z, 50000 rpm Maximum Speed
6    2    Each    1257K55    Rotary Shaft 303 Stainless Steel, 3/16" Diameter, 24" Long

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