Why does my class ring flip up when I spin it?

In summary, the ring flips up so the face is no longer in contact with the desk, but is facing skyward, and continues spinning, barely losing any momentum at all.
  • #1
ElijahRockers
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Just curious. Not sure if this has been discussed already, and I'm not sure what the phenomenon is called, but here's a description:

I have a heavy gold class ring that I got from my alma mater. I put the ring face down on the desk, flat, and it can rest like that because the face of the ring is flush with the desk. The ring face is a flat oval-shaped face about 1cm in diameter.

Now I can 'spin' the ring, like you would do with a coin or a top. Very quickly, the ring, while spinning rapidly, somehow flips up so the face is no longer in contact with the desk, but is facing skyward, and continues spinning, barely losing any momentum at all. I have tried to watch the transition carefully, at some point the ring MUST be completely sideways right before it flips up, which is just seems kinda crazy to me.

Why? Probably something basic, but as an EE I don't do a lot of mechanics, and this has been a question rattling around in my head for a long time.
 
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  • #2
Clearly the heavy side down is some kind of unstable state, which falls into the stable state of the heavy side being 'up' while spinning... it just seems counter intuitive that the center of mass should be at the top of the system. Or am I thinking about this incorrectly?
 
  • #3
Answer A: You went to the wrong school. My ring doesn't do that:

0706_brassrat_copy2.jpg


Answer B: This is a variant of the "Tippy Top". The full solution is complex, but here is an outline. If you perturb the top (I will call the ring a top, because it's clearer) the point of contact with the ground will not be the same as the rotational axis. This applies a torque to the top, which if large enough will flip it. This raises the center of mass, and the energy has to come from somewhere. The only source is the rotational kinetic energy of the top, so the top slows down. In the process, it loses angular momentum (ultimately, to the ground). Now it can't reverse the process - energetically it's allowed, but the top no longer has enough angular momentum to spin in its original orientation. So it continues to spin heavy-side up.
 
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  • #4
Vanadium 50 said:
You went to the wrong school.

I beg to differ!
cc993226495a750da95f78475cad19ae.jpg

Vanadium 50 said:
My ring doesn't do that

Are you sure you're spinning it hard enough? What does it do instead, just keep spinning on it's face?

Vanadium 50 said:
This applies a torque to the top, which if large enough will flip it.
But surely that doesn't happen in one fell swoop, I can clearly see the ring does almost a slow transition from face down to face up. It must be some kind of periodic, recursive function, I assume
 
  • #5
ElijahRockers said:
, at some point the ring MUST be completely sideways right before it flips up, which is just seems kinda crazy to me.

If that bothers you, don't think about the direction the ring or top is spinning in. That will really mess you up.
 
  • #6
Vanadium 50 said:
If that bothers you, don't think about the direction the ring or top is spinning in. That will really mess you up.

Oh god.
 
  • #7
My ring is very difficult to spin because of the flat face. And the motion of a top (even a non-tippy top) is quite complicated, with precession, nutation, polhodes, herpolhodes and invariable planes. I described the beginning and the end. The middle is complicated.
 
  • #8
Vanadium 50 said:
My ring is very difficult to spin because of the flat face.

So is it just the fact that it's a square face, as opposed to a elliptical face? Because my ring also has a flat face.

It's times like these that I wish I had a slow motion camera.
 
  • #9
Through the power of Google-Fu


BoB
 
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  • #10
God bless you, and happy new year. /thread
 

FAQ: Why does my class ring flip up when I spin it?

1. Why does my class ring flip up when I spin it?

This is due to the ring's center of mass being positioned above the point of rotation. When spun, the ring's weight causes it to flip up and over the point of rotation, resulting in the flipping motion.

2. Can I prevent my class ring from flipping up when I spin it?

Yes, you can adjust the ring's center of mass by adding or removing weight from different areas of the ring. This can be done by resizing the ring or adding gemstones to one side.

3. Why do some class rings not flip up when spun?

This is likely due to the ring's center of mass being evenly distributed around the point of rotation. Rings with symmetrical designs and weight distribution are less likely to flip up when spun.

4. Is the flipping motion of my class ring harmful to the ring?

No, the flipping motion of the ring is not harmful as long as the ring is made of durable materials. However, excessive spinning may cause wear and tear over time.

5. Does the size of my class ring affect its flipping motion?

Yes, the larger the ring, the more likely it is to flip up when spun. This is because larger rings have a higher center of mass and more weight, making them more difficult to balance on a single point of rotation.

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