Under the ruler faster than the ruler

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Another model demonstrating the principle of the cart that moves down wind faster than the wind. Inspired by some ideas posted on the discussion at forums.randi.org, I made a simple cart that is propelled underneath a moving surface, faster than that surface. The large wheel, turning against the direction of movement of the ruler, is very similar to the propeller of the wind-powered cart, turning against the wind. The next episode is here: http://www.youtube.com/watch?v=9Yt4zxYuPzI PS. Several people have asked where Louise comes from. She was made in Sri Lanka for Barefoot: http://www.barefootusa.com/NewFiles/toys2.html If you want to read more about downwind faster than the wind: http://peswiki.com/index.php/Directory:Directly_Downwind_Faster_than_the_Wind http://dwfttw.blogspot.com/2008/12/comments-questions-disagreements.html http://en.wikipedia.org/wiki/Sailing_faster_than_the_wind#Sailing_dead_downwind_faster_than_the_wind

Comments from Youtube

Matthew Maciej : I didn't hear the animals say anything,my sound must be broken.

TMAH : You have a remarkably calming voice. 

Robert Warren Gilmore : Coolaun! Where did you go? I would love to see more videos.

Amplitude Maximum : well that was a creepy demonstration

Bryson : I found this video when YouTube was barely starting to get popular and before ASMR was popularized. I remember I fell asleep to this video but lost it and never found it for at least 10 years. I can not believe I found this video again my mind is blown

jasminamuffin : thank u tichy this vid is 10/10

Fred Kellermann : dude knows how to divide by zero

Blopartyhut : This is sorcery. Burn this man and his demonic contraptions at once I say!

kittenesque : every so often I come across this video, and, having forgotten the results from the last viewing, get it wrong. it's still interesting, and gave myself and my roommate an interesting conversation because I still remember how it works

Mercenary Tao : no way it moves that way unless u hold the ruler under an angle.

prosthesis_ : Explanation?

Sidney Law : Best name for a machine, ever.

enndubful : Draw the free body diagram people. It's obvious it will move in the direction of the ruler. Then you look at the gear ratio and see how much faster it goes.

MagicalKarriya : Terry! ya chump!

Joey Vigil : Wow, l lets me just explain this because all other explanations having to do with friction and forces are wrong. A simple diagram of this effect would be a stationary rack gear (teeth in a straight line), connected to a spur gear 1(circle gear), connected to a spur gear 2, connected to a rack gear that is fixed to be parallel to the first. Now imagine that that the two spur gears are the same size. What happens in the situation? as you turn spur gear 1, spur gear 2 spins at the same "speed" and the rack stays in the same position. now imagine that spur gear 1 has more teeth than spur gear 2. As spur gear 1 turns clockwise, spur gear 2 spins counterclockwise at a higher "speed" and and the rack ends up going the opposite direction as the two gears. Now finally the third situation is the one in the video. Spur gear 1 is smaller than spur gear 2 and the gears go the same direction as the rack.

silky gold : I'd let you read me a bedtime story.

Ag3ntW1nd3x : kush

TD : Soon this will be on Brain Games @ nat geo. ~_~"

Wigwam : Dat asmr tho

Thomas Åhlén : This video rules!

Baxter Stockman : Counter-clockwise.

UDT116 : Lateralus.

dirty norris : The animals giving different answers is super cute

NightwingASMR : Very interesting! Funny how physics work.

Xelt4 : terry is a smug little shit

yellowfolder : dumbass

ajpal : Say the small wheels couldn't spin. Moving the ruler to the right would just drag the contraption to the right at the same speed because of the friction between the ruler and rubber wheel. But the wheels CAN spin, so it gets dragged to the right at the same speed, which spins the small wheels clockwise, which spins the big wheel counter-clockwise moving it even further to the right.

KCToon the man : The cart has little carts.

TeckyTim : What happens if you take the rubber off the big wheel?

Robert Patterson : what a voice

Anakie : bitch ass terry knows all

Xaphan6669 : god damnit stumbleupon! now i need to understand why this does what it does.

piratewoodleg : The cart in your link is upside down compared to this one. The big upper blue wheel here, corresponds to the small bottom red wheels in your link. Their size doesn't matter. What matters is the size ratio of the wheels that have 2 radii (reels here and black/green wheel in your link)

jpdemer5 : Wrong. See video at h++p://sifter.org/~simon/journal/20101107.h.html

jpdemer5 : Mathematically, there's no limit to how fast the cart can go. In the real world, there's a limit to how big the big wheel can be, and there's a limit on how much horizontal force you can apply to the big wheel. There's a nice animation, where the "ruler" has teeth that engage the big wheel, at h++p : // sifter.org / ~simon / journal/ 20101107. h. html

Horhay Fernandez : My brain just exploded

UFO_Robert : You sound kind of like Tyrion Lannister from Game of Thrones in certain parts of this video.

Frabjous : You sir, are so captivating, and yet you could snap your finger and I would fall asleep. Your voice is perfect.

Juana Tinkabowdit : it is not easy for over 70% of the viewers and commenters to see the lower side of the ruler is having a small bit of pressure put onto it, pushing the mechanism forward, visually he is also moving the ruler whilst carrying the pushing process, out.

solitaryman098 : I'm out, you guys win.

The Robot : Why'd you have to spoil the answer with the title?

mazhas08 : explain that atheists. atheists: 0 jesus :1

DOitTOtheCROWD : I CANNOT INTO BRAIN. I HAVE THE DUMB

PuggleKid : SORCERY!

GOLDshred : Fuck i'm dumb -.-

AlephNeil : For anyone who is both (i) confused and (ii) knows high school algebra, let's break this down like a textbook exercise: 1. Suppose the inner radius of the lower wheel, at the point where the big wheel touches it, is r, and the outer radius of the lower wheel, where it touches the ground, is R. Show that, unless the wheels are slipping, (the speed of the cart relative to the ruler) = (r/R) * (the speed of the cart relative to the table) 2. Define F(x, y) to be the rightward speed of the cart if the ruler is moving right at speed x and the table is moving right at speed y, and the wheels are not slipping. Using the previous exericse, show that for all v, F(rv, Rv) = 0.   (Remark: We can interpret v as the angular velocity of the small wheels.) 3. Given the result of the previous exercise, explain why it must be true that F(rv + k, Rv + k) = k for all v and k. (Hint: Imagine that the entire room and everything in it are moving right at constant speed k.) 4. Suppose that the ruler is moving right at speed 1 and the table is not moving. Solve the simultaneous equations rv + k = 1; Rv + k = 0 for v and k. Deduce that the cart must be moving right at speed R / (R - r), which is > 1 (therefore 'faster than the ruler').

Rezileen : Everything here is real folks. It's just a result of some nice physics. For those confused, notice how the big wheel is touching the smaller wheels. It's not actually touching the outside rim of the small wheels is it? It's touching the "insides" of the wheels if you get my drift.

Karkenou : Your voice is so soothing! You would make an excellent educator!

Justin Hampel : Look at his other video, "Under the Ruler 3: Tilting the Ruler." He shows in the video that tilting the ruler does not determine which way the cart will move.