What happens when a bullet hits an 'unbreakable' Prince Rupert's drop?
For those of you who aren't familiar with the Prince Rupert's drop, this weird, scientific enigma is a glass object that's created by dripping molten glass into very cold water.
Is a teardrop-shaped piece of glass that's pretty much unbreakable at its bulbous 'drop' end, but which shatters from the slightest pressure at the elongated tail end. Scientists have been obsessed with them since the 1600s. But what happens if you shoot one with a bullet?
In glorious slow motion, you can watch as the bullet bounces right off the wide end of the drop, sending out shock waves that then rattle the rest of the structure and cause the thin end to break, resulting in the entire thing exploding.
When the Prince Rupert's drop is made, molten glass is poured into extremely cold water, causing the outside of the drop to cool and solidify almost instantly, while the inside remains molten and cools more slowly.
Because of thermal expansion, glass wants to expand while it's hot, and contract while it's cool.
That means that as the molten inside of the glass gradually cools down, it wants to contract and pull the solid outer layer inwards. But because the outer layer is already solidified, this just makes the whole thing tighter, making that bulbous end of the Prince Rupert's drop pretty much indestructible, and, as we now know, bullet-proof.
But because the outside of the glass is in extremely high compressive stress, and the inside is in extremely high tensile stress, if one link is ever broken, then the whole thing explodes, feeding off its stored internal energy.
This is what happens when the fragile thin end at the back of the drop gets broken - it releases all that pent-up energy and causes the whole thing to shatter.
Video source via Smarter Every Day:
https://www.youtube.com/watch?v=24q80ReMyq0
Story via ScienceAlert
http://www.sciencealert.com/watch-what-happens-when-a-bullet-hits-an-unbreakable-prince-rupert-s-drop
What is Prince Rupert's Drop anyway?:
http://www.businessinsider.com/the-physics-of-prince-ruperts-drop-glass-smashing-2015-6
#physics #science #princerupertdrop
Oh that's an easy fix. I know just the right glass blower that can do it.
ReplyDelete#amazing #MindBlown
ReplyDeleteRemarkable!
ReplyDeleteThey're also kind of neat because you can take one and put it on a anvil and whack it with a hammer and hammer dents into the steel anvil without hurting the glass. But as I learned when I was a kid, it's a waste of time to make a bunch and keep them in a box so you can show them to friends, because three months later when you open the box it's just full of tiny glass shards: they aren't long-term stable.
ReplyDeleteHow is this PRD unbreakable?
ReplyDeleteThe video links to another video that explains it.
ReplyDeleteThe problems with the Prince Rupert's drop is that it has that tail. If one could make a near perfect sphere, it would be nearly unbreakable. How would you make a perfect sphere? Make it in Space!
ReplyDeleteBuild a radiation oven in the vacuum of space, with a blob of glass floating in it, with no relative velocity. The oven melts the glass, which relaxes into a sphere. The oven is turned off, the door is opened and the oven moves rapidly away from the sphere. The sphere emits radiation, cooling the surface more rapidly than the interior, and the glass is tempered, resulting in a ....
Prince Rupert's Space Drop!
Or hit it from several angles with cold gas, Captain Jack, and make bearing balls with unparalleled sphericity and fabulous wear resistance cheaply (if you don't count the cost of getting the equipment up there.)
ReplyDelete