[Youtube Review][Veritasium] Spinning Disk Trick Solution

(Recommended)Popular Videos : [Veritasium] Spinning Disk Trick Solution

 

This time, I will review the popular YouTube videos.

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(Recommended)Popular Videos : [Veritasium] Spinning Disk Trick Solution

https://www.youtube.com/watch?v=tDr26U49_VA

 

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Playtime Comments : [Veritasium] Spinning Disk Trick Solution

Er********:

0:20 The greatest minds in modern physics and not one of them thought, "If we spin this on a table or work bench, we can see it better, and we won't need to bend over like this."

Th***************:

3:45 here it's because of the Intermediate axis theorem, as well as in the case of low friction

Os*******:

Here's what i think is happening:
As the disc spins it leans to one side and starts rolling, changing the orientation of the cut out hole from top to bottom. If you spin a coin, as it slows down it starts leaning to one side and starts rolling on the spot at a 45 degree (or so) angle, rather than spinning completely upright.
A good example in the video is at 2:28, you can see a predominant lean to one side (the side with the tape) start to develop, this causes the disc to effectively start rolling in a very tight circle and you can see that the point of contact with the ground is moving in a tight circle beneath its center of gravity.
Further evidence in the video, if you look at 2:32 the disc is upright and shows no sign of rotating over. It is only at 2:35 when the disc loses balance and starts leaning to one side that it actually starts rotating; surely if it was flipping due to inertia or centripetal force then it would start rotating immediately after it is let go?

Please share your thoughts as a comment, tell me if I'm wrong, tell me if im right.

Me*******:

1:55 he does looks like science

Sh*******:

0:51 that got me laughing

Ev*******:

3:55 What are thoooose...

 

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Top Comments : [Veritasium] Spinning Disk Trick Solution

Jo*****:

Try it by painting a spot instead of cutting out a spot and see if it still behaves the same way.

An************:

How about some controlled experiment, like mounting that thing in a bearing mounted on an adjustable axis and spin it up with a good blast of air. To go further start in a sealed chamber and then suck the air out.

Ad***********:

In my opinion , i think the air through the hole is playing a major part in the transition , what do you say about it guys ?

Pe********:

I decided to build a tippie top in my shop because of this video. I'm now subscribed to your channel and have thoroughly enjoyed catching up on your videos.

me*****:

found another glitch

Ra***********:

Couldn't it be because of the "intermediate axis theorem" also known as the "tennis racket theorem"?

Sa***:

The best way to deal with problems like this is using lagrangian mechanics to look for stable equilibria. You basically think of the full configuration of the system as a point in space, and look at how the energy will change if you make small movements. Although both the hole at the bottom and top would be equilibrium points, the hole at the top is not a stable one. It's been ages since I was a student and we worked out these spinning top problems, and I don't really have time to do it all again now, but it actually becomes pretty easy to understand these systems when you look at things using generalized coordinates and the principle of least action rather than trying to work things out using forces. Energy-based reasoning turns out to be much easier than summing forces if you want to analyze and understand most rigid-body systems.

He*********:

I don't pretend to be smarter than anyone else, but I just figured this out on my own when watching the video for the 1st time :|

Gr*********:

What would happen in micro gravity?

Ba***********:

there is also the conservation of energy here where it gains potential energy from haveing the heavy side up

DE*********:

He finally solved it in 2019... Watch the video titled something like. 'The bizzare behavior of spinning bodies '

Ho*********:

I have a suggestion
Make this model on 4 different axis to form something like a ball with a hollow ball at some side
That will eliminate 2 axis factor of unbalance and a lot of other factors. If the greater mass tends to go to the top which is expected as in the toy you mentioned I guess that will totally mean inertia is the main factor.
I'm just an architect and I have no idea what I'm saying.

Sl**********:

It has to do with balance. To explain in a "hands on" sense, take a broom and balance it on your hand, counter-intuitively it's easier to balance it with the heavy side up...that's because a heavier object is more difficult to move than a lighter object...but you're controlling it not at the top side, but at the bottom. Same as the spinning disk. The demonstration on the ice removed the focal point so there was no balance due to a lack of friction, So the answer was inertia and centripetal force...and the conservation of energy. Inertia dictated how best to conserve the centripetal force.

Ba********:

Just eat cake, it's easier.

Ke******:

The spinning disk differs from the tippytop, though. The tippytop has a central axis upon which to spin, keeping all of the matter evenly distributed, while the spinning disk has a hole interrupting the central axis, with matter distributed unevenly around it. The disk wobbles more as a result. Regardless of which toy is used, rotational stability matters. With more mass at the base, the center of gravity is lower, but the length of the axis above the center is greater. Axial variation is exaggerated over the longer distance and has a greater effect on rotational stability. With more mass at the top, the center of gravity is higher. The axis above the center of gravity is much smaller and insulated by the greater mass, so axial variation has less distance to be disruptive. Ice causes trouble because it undermines the stability of the axis at the base. Unlike a tippytop where the axis centers around a very small point of contact, the spinning disk has its entire circumference to use as a point of contact.

Ba******************:

Solution: ehhh, not sure.

Am********:

I'm guessing, not completely sure, but I think maybe it has something to do with the alignment and relative positions of Centre of Gravity, Meta Centre and Centre of Buoyancy... An object when immersed into a fluid (which is air here) is under Stable Equilibrium if it's Centre of Buoyancy is below the Centre of Gravity, otherwise it will have Unstable Equilibrium and it will try to attain stable equilibrium while it can (i.e, in this case, while spinning).
Eg: An egg shaped dense object will sink into the water with it's larger side in the bottom. No matter how much you try you will not be able to make it sink down with its smaller side down... (which is quite opposite in this case... I know I'm contradicting my own statement... my physics is bad... forget you even read all this lol :P )

Je**********:

now what about the air that travel through the hole?? it might affect the air friction right ??

Pr**********:

Finally that bloody youtube recommend me this after 8 years

bd*****:

"I'm buggered if I know why." Classic.

Is********:

spin that in a vacuum and you got the answer

Am*******:

Actually It's Not Just Surface Friction !
The Air Has Friction Too And As Its Even More Connected To The Air The Air Force Is More Effective Than The Surface !
But The Ice Hall Is Cold More Air Molecules Are Packed So That Is Puzzling For Me :-(

Tr*********:

A way to perhaps improve on this experiment could be different sized holes, I think.

Sm*******:

Before I hear the answer I’m guessing that it’s because it’s center of mass is at the solid part

ba*******:

an interesting phenomena in space --- google "Dancing T-handle in zero-g, HD" - something similar to your ice experiment I think.

ja***:

Isn't it the same reason that a tennis racket spins over the x-axis when you flip it over the y-axis? I thought either you, Smarter Every Day or Mark Rober made a video about that fenomenon.

Al*********:

i like how he finds out everything, out of curiosity and only through his effort. it's so cool

Ra*********:

For a 13 year old, I have no idea what I'm doing here.

Ma*******:

“Why dont i have any hair in that?”

Se********:

Centrifugal force is non-existent, its just an under educated persons word for inertia when in the presence of a centripetal force

Ma*******:

I'm surprised that nobody speaks of two factors :
first the anti-slipping force on the part that touches the table (the handle of the tippy top)
and second the fact that the centrifugal force pulls the heavier part horizontally. But I don't know what acts to pull that heavy part HIGGER than the horizontal diameter and the remaining part. Probably a force due to the slip on the support plane. But are we sure it slips or does it roll without slipping ?

Sc**********:

I think I understood it :).. It is kind of related to stuff like the gimbal lock phenomenon...

Firstly, the spinning forces a Gimbal Lock situation on the wheel..

Since the 'two circles' (one 'positive' and one 'negative' (a hole)) are on the same plane, they will share the rotation..

But the larger circle is 'unlocked' (you can spin it any way you want), and the smaller circle ('hole') is 'locked' (you can not spin the hole).. The rotation axis will be the same for the two circles, but for the smaller circle, the object is dislocated from its center of rotation (from the rotation axis)..

This axis offset, combined with the gimbal lock will force a Y rotation for each Z rotation angle until it is really 'locked' (the smaller circle on its most lower position).


Well, i think this is it =D...

My********:

Like so Derek sees:

As the disk wobbles, the point on the disk that would be touching the ground if it was straight up and down suddenly isn't touching the floor. So, the forces that collectively have been misnamed centrifugal force pull that part outward until it is at the equivalent of the disk's equator. After this, gravity acting on the disk pulls the point down 90 degrees ahead of where it is at that moment (check out vsauce's spinning video for that explanation) eventually causing the point to be at the top. This explanation explains the ice and midair spinning and after this the entire thing happens in reverse. I hope this helped.

Vi************:

My best guess would be that it has something to do with self-stabilization, like a gyroscope. Rotating any round object with a point, and it will try to remain centred no matter what outside forces affect it, the same would apply here. The problem is that you cannot spin it perfectly upright with your hand, as when you let go, you must imply some inclination on it, setting the centre of the mass off balance, making the disc try to stabilize itself. I imagine that, if you could make this disc rotate fast enough, you would be able to make it flip and it would simply continue to spin like a quarter until it loses enough speed to lose centripetal stability. Who knows, it might be the answer, part of the answer, or the exact opposite, but isn't that the fun in science?

 

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[Veritasium] We gathered comments about popular videos and looked at them in summary, including play time, and order of popularity.

It's a good video or channel, but if you're sad because it's too long, please leave a YouTube channel or video link and I'll post it on this blog.

 

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