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This is an Euler's Disk

Khufu says...

in space? I think gravity is the primary instigator here, so in space you'd need to do this under intense acceleration or in a centrifuge to get similar results. it's just taking a really long awkward way to fall:)

BSR said:

I would be interested to see what would happen just before the disk stopped and suddenly there was no gravity. Even though it sounds like it's spinning faster I'm sure it's just because the edge of the disk is just closer to the mirror.

Suddenly without gravity would the energy cause the disk to rotate making it look like a ball floating in space or would it wobble and take off in one direction?

Could this even be done in space?

Are there any mathematicians in the audience tonight?

Are four questions in a row too much?

We Still Don’t Know How Bicycles Work

newtboy says...

I must disagree.

First, it's precession, not procession, paired with the "caster effect" and static friction. It's a self correcting system that only works when in forward motion.
This nonsense with counter rotating wheels countering the gyroscopic effect ignores the fact that only the forward rotating wheels are using friction to direct the path of the bicycle based on their angles. It's not JUST the gyroscopic effect, that only determines the resistance to angular change, it's friction directed by gyroscopic precession and the self correcting caster effect. Come on.

Nobody knows how we ride bikes?! (A different claim from we don't know why they can remain upright when ghost ridden) Nonsense, it's balance plain and simple. If you don't keep the center of gravity exactly above the contact points with the ground, you tilt. When the centrifugal force exceeds static friction of the tires you slide out or when gravity exceeds the opposing centrifugal force caused by turning, you fall. Try turning your bike but staying exactly upright, no lean. Now, when you heal, try leaning without turning, lock the wheel straight, you'll fall again. It's multiple forces in concert.

I think a decent physics teacher would wipe the floor with this. It ignores so much to make these "we just don't know" claims.

Spinning Swing Challenge

oritteropo says...

The yt info is:

Le projet le plus fou de l'été !
Le premier tourniquet tracté par des bœufs en plein milieu d'un lac. Les règles du jeu sont simples sur ce drôle de manège : qui tiendra le plus longtemps !?
Grâce à un système de déclenchement fait avec 2 mousquetons de largage, dès qu'une personne lâche, la corde glisse et l'autre est automatiquement larguée. Au final, la force centrifuge était telle que personne n'a réussi à tenir au delà des 30/35 km/h !


Or, in English:
The craziest project of the summer!
The first ever roundabout (literally turnstile, means something like the rotating swings in children's playgrounds) towed by oxen in the middle of a lake. The rules are simple on this amusing ride: Who will hold on for the longest!?
Thanks to a trigger system made with 2 release carabiners, as soon as a person lets go the other is automatically released.
In the end, the centrifugal force was such that nobody managed to hold on beyond 30/35km/h (approx 20mph in U.S. measures).

moonsammy said:

Tried to watch it closely, but couldn't figure out how they had it rigged to release the 2nd person once the 1st drops off. Impressive!

Mordhaus (Member Profile)

How to save 51B lives for 68 cents with simple Engineering

Nobody's Exactly Sure How Much A Kilogram Is Right Now

MonkeySpank says...

This only applies to the metric system. For the empirical system, it gets even more confusing. Here's a simple quote from NASA's Pre-Jesus era website:

The effective acceleration of gravity at the poles is 980.665 cm/sec/sec while at the equator it is 3.39 cm/sec/sec less due to the centrifugal force. If you weighed 100 pounds at the north pole on a spring scale, at the equator you would weigh 99.65 pounds, or 5.5 ounces less.

Whenever we talk about weight in pounds, we need to define where with respect to the center of our little bluey.

Chinese Street Food - Cookie Tosser

dannym3141 says...

I was completely baffled by how he manages to make all the cookies move away from each other. I had a moment where I was completely confused and thinking it was impossible or CGI.

Then the gears started turning again and I realised he could be spinning the wooden platter with the axis at the centre of all the cookies and using the centrifugal force - which I thought was interesting.

Neodymium Magnets Reaching Terminal Velocity

MilkmanDan says...

Ahh, but the magnets don't actually *disintegrate*... Maybe "centrifugal separation".

Still, I like the cut of your jib.

Payback said:

It's the thin edge of the wedge. Inaccuracy in online video titles mean the terrorists win!

All because the OP couldn't think of "centrifugal disintegration".

Neodymium Magnets Reaching Terminal Velocity

Payback says...

It's the thin edge of the wedge. Inaccuracy in online video titles mean the terrorists win!

All because the OP couldn't think of "centrifugal disintegration".

MilkmanDan said:

...perhaps an online video about magnets spinning apart can be at least partially excused for opting for brevity over accuracy...

Neodymium Magnets Reaching Terminal Velocity

MilkmanDan says...

@Payback -- The Youtube comments area is not to be considered a potential source of rational discussion.

Assume that one concedes to your point about "terminal velocity" being the wrong phrase to use here. What would be better? And I'll note that there are many potential metrics for "better" -- conveying the correct idea precisely, doing so in a concise manner, etc.

"Neodymium Magnets Reaching a Velocity at Which the Centrifugal Force Upon Them Exceeds the Magnetic Force Holding Them Together" makes for a more accurate title, but might lose brevity points. The "Terminal Velocity" title conveys maybe only 75% of the accuracy of the more precise title, but with a greater than 25% savings in length (5 words vs 19). Although I'm sure a more optimally brief AND accurate title exists.

Not trying to be snarky, and I 100% agree that there are situations where saying something with complete accuracy and careful precision is extremely important. But perhaps an online video about magnets spinning apart can be at least partially excused for opting for brevity over accuracy, especially in something as trivial as the title. Especially when the inaccuracy can be noted and explained in the comments section by well meaning viewers.

Neodymium Magnets Reaching Terminal Velocity

MilkmanDan says...

True, but "terminal velocity" conveys decently close to the right idea and there isn't any specific word that means the speed at which magnetic force is overcome by centrifugal force. As far as I know, anyway.

Escape velocity ("the lowest velocity that a body must have in order to escape the gravitational attraction of a particular planet or other object") might be arguably closer to the mark, but gravity is not the same as magnetism.

Payback said:

Terminal velocity does not mean what you think it means.

It's the speed that a falling mass achieves equilibrium between the force of gravity and the force of fluidic drag and stops accelerating. It's not the speed required to "terminate" a thing.

Coach Makes Nice Save

Payback says...

Part reaction, mostly experience. He obviously knew she was getting into a high-centrifugal-force point and her hands might slip as he moved forward ahead of time. The tumble to keep from squashing her was an excellent touch.

Going to the fair in China!!

Going to the fair in China!!

Going to the fair in China!!



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