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  • At the Palace of discovery in Paris, they

  • have this huge turntable where you can

  • sit, and perform experiments. Like in the

  • middle of the turntable you can put some

  • water and then add liquid nitrogen, and

  • this creates a kind of fog these tiny

  • water droplets that spread out from the

  • middle, but because the actual linear

  • speed of this turntable is increasing

  • the further out you go well, the vapor

  • falls further and further behind

  • creating a swirl, that looks a little bit

  • like a Hurricane. And that analogy is not

  • by accident, the Earth is after all one

  • giant turntable, and the weather patterns

  • we get are a result of that. When you

  • study Physics in rotating frames of

  • reference, or even just rotating bodies.

  • You find some pretty mysterious and

  • counterintuitive phenomena, which is why

  • I'm dedicating this video to four

  • revolutionary riddles. Number one here I

  • have a ramp, or an inclined plane and

  • just to show you i'm not doing anything

  • funny with it, if I just let a roll of

  • tape go it will accelerate down the ramp.

  • But! Here I have a mystery cylinder, and

  • I'm going to place that on the ramp, and

  • we will see that it rolls, and then it

  • stops, and then rolls, and then stops. So my

  • question to you is. What is In the

  • mystery cylinder? What is this object?

  • Number two, take a bicycle and have

  • someone support it, so it doesn't fall

  • over or lean it up against something, and

  • then take a bit of string and tie it to

  • the bottom pedal. Now what I'm going to

  • do is pull backwards horizontally on

  • this string, and I want you to predict

  • what the bike will do. Will it go

  • backwards? Forwards? Or will it just stay

  • there and not move. My intuition would

  • tell me that it would go forward? I think it

  • might not move if you're going to be

  • pulling backwards from a stationary

  • point on the pedal, you're going to be

  • pulling it backwards just as the pedals are tying to

  • spin the wheels forward, so maybe

  • it might not move. Things gonna go

  • forward, I'll go forward. Sure? Yeah, I'm

  • sure. all right three, two, one.

  • Number three. I want you to think about running two laps of

  • this track now the first lap you can go

  • as slowly as you like, let's call that

  • speed V1. But on your second lap, I want

  • you to run faster. Such that the total

  • average speed for both laps combined is

  • twice V1, twice the speed of your first

  • lap so the question for you is. How fast

  • do you have to run that second lap, so that

  • your total average speed, is two V1?

  • Number four, any time a train is moving, either

  • slowly or very fast. There is a part of

  • the train which is actually moving

  • backwards with respect to the ground,

  • that is not backwards with respect to

  • the train, and it doesn't have to be

  • going so slowly that if you ran

  • backwards you would be going backwards

  • with respect to the ground. It is at any

  • speed, any normal train will have a part

  • of it, which is moving backwards with

  • respect to the ground. My question to you

  • is. Which part is it? now with these four

  • riddles, you can make me a video response

  • if you like to tell me about your

  • solutions to them. Or you can simply

  • leave your answers in the comments below

  • and number them 1 2 3 4 so we know which

  • ones you're talking about, and I will

  • post all of the answers up and next week

  • at the same time same place.

  • All of my videos are made possible by my Patrons

  • on Patreon, so if you are one of those

  • people. Thank you so much for your

  • ongoing support, and if you're not. Maybe

  • now is a good time to consider becoming

  • one, if you go to Patreon.com/Veritasium

  • you can support me there.

  • Otherwise, if you're interested in more

  • riddle-y puzzling things, you can check out

  • my Spinning tube trick, my 5 fun physics

  • phenomena, and say the spinning district

  • and if you haven't subscribed Veritasium

  • already I highly recommend you do that.

  • And since i'll be posting the answers

  • next week I would like for you to ring

  • the bell down below, and that will make

  • sure that you're notified

  • when my videos come out. So as always,

  • thanks for watching wait that's, that's

  • Michael's line.

At the Palace of discovery in Paris, they

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