Is this what makes clear plastic card sleeves stick together? I always figured it was static electricity but maybe it's this?
Wringing
61–70 of 78 posts
Re: Wringing
#62This got me wondering, (and I know it's probably not a physics question). If I scrape two fingers and press them together for a week. How do the skin cells know which other cells to attach to when healing? Or will I have one super finger?
They can grow together but will take longer than a week. There's a man the had his hand degloved and they sewed it into his stomach to heal, after which they cut his hand back out and used his stomach skin to wrap around and reshape some resemblance of a hand.
Example 1: https://www.thesun.co.uk/news/4303135/surgeons-save-hand-sew...
Example 2: https://www.menshealth.com/health/a19517212/carlos-mariotti-...
Re: Wringing
#63Earlier quoted context omitted.
You can use them in concert with a Sine bar to create precise angles https://en.wikipedia.org/wiki/Sine_bar
Sine bar in action: https://www.youtube.com/watch?v=PO-Ab7YfBzY
Check out this alternative version of a sine bar https://observablehq.com/@jrus/sinebar
Also includes some nice youtube videos inline for context.
Re: Wringing
#64This got me wondering, (and I know it's probably not a physics question). If I scrape two fingers and press them together for a week. How do the skin cells know which other cells to attach to when healing? Or will I have one super finger?
This is the origin of the concept of a skin graft, surely.
That's how it works basically yes.
https://www.royalfree.nhs.uk/services/services-a-z/plastic-s...
Re: Wringing
#65Isn’t this the same effect as the screen protectors we all have on our phones?
Re: Wringing
#66This got me wondering, (and I know it's probably not a physics question). If I scrape two fingers and press them together for a week. How do the skin cells know which other cells to attach to when healing? Or will I have one super finger?
They can grow together but will take longer than a week. There's a man the had his hand degloved and they sewed it into his stomach to heal, after which they cut his hand back out and used his stomach skin to wrap around and reshape some resemblance of a hand. Example 1: https://www.thesun.co.uk/news/4303135/surgeons-save-hand-sew... Example 2: https://www.menshealth.com/health/a19517212/carlos-mariotti-...
Wow. Can you imagine how that would feel, to have your hand inside of you? I'd worry about accidentally breaking something inside me. Amazing though.
Re: Wringing
#67Earlier quoted context omitted.
There's something at play that causes precision ground surfaces to stick together. Oil certainly plays a part, but there's a point that when two surfaces are flat enough, they'll stick hard in place, and there's a "crack" moment when twisting them apart. Around a decade ago, I worked in a machine shop. Mill table surfaces are ground flat. Not precision surface flat, but good enough to be a reference for cutting tools…
> Mill vise clamping surfaces are ground flat. It's normal for an object that's at least cut (not even ground) flat on one side to get hydraulically suctioned via cutting oil to either of these. It's usually easy to slide the part off to the edge of the surface. Like you say, this is a hydraulic/air pressure effect- it's related to why you can float things on a reference plane: https://www.youtube.com/watch?v=Kj6jmQx…
> Indeed they do: https://youtu.be/_YVWdxr0E_g?t=155
What a fine example of the white labcoat as an authority prop!
Re: Wringing
#68Great stuff. We need more of these types of science tidbits on HN. And good links by the commenters too. I love Feynman's classic style of "explaining to a 5 year old" on Cold Welding. The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and grea…
Note that this is a big oversimplification- it doesn't apply to gage blocks. Cold welding and similar phenomenon can only truly happen with metallic bonds and very large grain sizes. Non-metallic bonds are structured and require precise orientations and conditions to reform. Metals are still structured -metals have crystal grains- and the microscale structure needs to line up in order to reform. In cold welding, you…
Well yes, wringing and cold welding are distinct phenomena. Breaking a cold weld will make the surface ugly, but getting two wrung gage blocks apart will not.
You are talking about wringing, Feynman was talking about cold welding.
Re: Wringing
#69Great stuff. We need more of these types of science tidbits on HN. And good links by the commenters too. I love Feynman's classic style of "explaining to a 5 year old" on Cold Welding. The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and grea…
Note that this is a big oversimplification- it doesn't apply to gage blocks. Cold welding and similar phenomenon can only truly happen with metallic bonds and very large grain sizes. Non-metallic bonds are structured and require precise orientations and conditions to reform. Metals are still structured -metals have crystal grains- and the microscale structure needs to line up in order to reform. In cold welding, you…
Wouldn’t it be fairly easy to eliminate water/oil and air from an experiment to see how it affects wringing? Air: try to wring the blocks in a vacuum or at high altitude to see if it is weaker/stronger than at sea level. Water/oil: clean the surfaces and do the experiment in a really dry environment.
Does wringing work with glass blocks? If so, could we then examine the interface with some type of instrument? Could we X-ray the ceramic blocks interface?
Re: Wringing
#70Earlier quoted context omitted.
Yep, admit I was a little taken aback after the drilled holes explanation. This seems correct, as no practically priced cymbal could be so precisely made.
I don't think they need to be precise; any reduction in the natural vibration can be detrimental to the sound. They never get "stuck" together, however, imnsho.
Yeah, I was saying that getting the surfaces to adhere sans vacuum seems unlikely for such an imprecise object