# 4 Revolutionary Riddles

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
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
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when my videos come out. So as always,
thanks for watching wait that's, that's
Michael's line.