Under the ruler faster than the ruler

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thatguywiththeegg : You're a witch.

Amplitude Maximum : well that was a creepy demonstration

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

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').

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

Bo Huggabee : the ruler is straight so it creates an illusion, and you forget to imagine the ruler as a gear turning. if you take the two points between which the wheel travels then curve that line, it become part of a gear and it's easier to imagine whats happening. . having two gears with one in between will result in the outer gears spinning the same direction. the trick to making it speed up is the different radius of the bobbins. clever trick.

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

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

NightwingASMR : Very interesting! Funny how physics work.

ACG : Guys its the angle of the ruler, He`s gently applying pressure to one side.

Horhay Fernandez : My brain just exploded

Gamakun : He is pushing down while moving to the right creating the opposite direction you expect it to move.

TMAH : You have a remarkably calming voice. 

jasminamuffin : thank u tichy this vid is 10/10

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

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.

Francis : This is all about friction. The friction between the little wheels and the paper is higher than between the big wheel and the ruler. If the friction between the big wheel and the ruler were higher than the little wheels and the paper, the cart would move to the opposite direction of the ruler.

Ag3ntW1nd3x : kush

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

Danny Stevenson : The animals giving different answers is super cute

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.

Yes I am sure I entered my name correctly. : For an educational children's video, this is rather intriguing.

Mark Telfer : Let's see him use the ruler to put pressure on the blue wheel, stick a pencil in the hub of the blue wheel and then try to move the pencil either right or left...and when mainline pressure becomes greater than governor pressure the spool valve shifts and the 1st/reverse clutch is released...nevermind, none of you want to become mechanics anyway. Go administrate and mistake it for managing.

Tiger Bauer : It's because there's enough weight from the ruler pressing on the top to move the whole unit since nothing is resisting the lower wheels. If you did the same thing but with only enough weight to affect the rotation of the large wheel the result would be what you'd expect.

Brian Deiss : Hi professor!

Nicolaf : Maybe your experiment would make sense if you did what you said you were going to do. You are moving the ruler in the opposite way. For example, moving the ruler to the right would make the center of the big wheel go to the left. Though at 2:10 when you say you are moving the ruler to the right, the center of the wheel, according to the ruler, goes to the right when it should go to the left, meaning you are actually moving the ruler to the left. The only reason the ruler SEEMS to be going to the right at this point is because of the difference between the diameter of the big and small wheels, making the kart go twice as fast on paper than on the ruler. This explanation is even easier to see when you are doing the ''tilting the ruler changes nothing'' experiment.

trekgeek1 : Here's a great way to visualize it. Imagine your computer screen is rotated 90 degrees. Now it appears the table is a wall. The ruler is another wall. The cart is stuck between the two walls and under the force of gravity, falls downward. When you visualize it as such, this is the only function that makes sense. In this configuration, the behavior is intuitive.

alasdair niven : Did nobody here ever take their bikes to bits as kids Google principles of epicyclic gearbox

Christopher Palmiero : Hey Prof Tichy

brian rees : There is a trick.  In order to begin the car's movement, the moderator must first move the ruler the opposite direction and then move the intended direction.  Assuming 100% perfect friction, to begin the car's movement to the right, he must first turn the big wheel.  Then as the car moves to the right faster than the ruler, relative to the wheel the ruler is moving left, but relative to the floor, because the car is moving faster than the ruler, the ruler is moving right ("to keep pace with the car") That is also why you run out of ruler.  they could not stay in contact forever at these different rates.

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

Antonio DS : George, Terry and Louise think that people who call it "anti-clockwise" should be violently dragged behind a dirty shed and shot in the mouth with a bazooka. I agree.

Fred Kellermann : dude knows how to divide by zero

prosthesis_ : Explanation?

Sidney Law : Best name for a machine, ever.

Zakk Hartwig : This could have some interesting applications!

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

Thomas Åhlén : This video rules!

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

Wigwam : Dat asmr tho

San Fierro : are you peter dinklage?

misterkel : How does this work with an iceboat?

Mindchime Official : optical illusion.  the cart moves the exact same distance as the ruler moves. 

MagicalKarriya : Terry! ya chump!

Baxter Stockman : Counter-clockwise.

Don Corman : This is fun, until one realizes that the ruler is not, in fact, moving in the same direction relative to the apparatus as it is to the observer. Once you realize that, the illusion is broken.

IMB2U : Terry please explain. Terry!

UDT116 : Lateralus.

rcmanization : could someone explain why the big wheel moves opposite to how you think it should move?

AcanLord : clever contraption. has this principle been used in any technology?