[HN Gopher] Does glass break faster than a bullet? [video]
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Does glass break faster than a bullet? [video]
Author : mfrw
Score : 50 points
Date : 2022-12-14 16:44 UTC (2 days ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| jkingsman wrote:
| Awesome video -- pretty low on fluff compared to how bad YT can
| get these days, which is a pleasant surprise.
|
| I totally understand the physics and reality of sound/light/etc.
| traveling different speeds in different mediums, but it's always
| such a wild thought to me. It tickles my brain in such a
| delightful way.
| version_five wrote:
| For anyone who doesn't want to watch an 8 minute video, the
| glass / bullet race is at 2:40.
|
| Maybe it's low fluff relative to other YouTube videos, for me
| it could have been a 5 second GIF without any real loss.
| permo-w wrote:
| given that (in physics) sound is vibration, I think a clearer
| way of phrasing it is that glass cracks at the speed at which a
| vibration can travel through it. glass is much denser than air,
| so the particles can knock into each other more easily, meaning
| that the speed of sound (or vibration) in glass is a lot faster
|
| (this isn't aimed at explaining it to you, just to write out my
| thoughts, as I found their explanation a little odd)
| satvikpendem wrote:
| Related, hitting a Prince Rupert's drop with a bullet:
| https://youtu.be/F3FkAUbetWU?t=104
|
| TLDW: The bullet shatters and the drop stays intact.
| mwilliaams wrote:
| So we should make body armor out of Prince Rupert drops?
| walrus01 wrote:
| I wonder what the results would be if done with a steel core/AP
| type rifle round , the bullet in the video appears to be
| jacketed plain lead at pistol velocities.
| sophacles wrote:
| The same channel did a follow-up with rifles here:
| https://www.youtube.com/watch?v=k5MORochIDw
| walrus01 wrote:
| For sure some very different results but it looks like
| they're using low cost jacketed plain soft lead. I wonder
| what the results would be with an M855A1 (available to
| civilians) or real armor penetrating designed round.
|
| https://smallarmssolutions.com/home/the-m855a1
| permo-w wrote:
| I'm surprised the fragments didn't cause the whole thing to
| shatter when they came into contact with the tail
| __MatrixMan__ wrote:
| I wonder how the speed of glass crack travel compares to the
| speed of sound in that particular kind of glass, and if the
| deficit can be accounted for by the fact that the cracks are not
| traveling in a straight line.
| nibbleshifter wrote:
| The shockwave (which travels ahead of the cracks) travels at
| the speed of sound of the material.
|
| I'd hazard a guess the shockwave propagates about twice as fast
| as the cracks.
| walrus01 wrote:
| Handgun rounds are really quite slow - now do it with a 5.56 NATO
| 55 grain FMJ from a 20" barrel at 3000+ feet per second.
|
| Basic rifle chronographs are under $200 and high enough Hz
| precision to measure feet-per-second of different rounds
| accurately. You still can't see it and differences are
| imperceptible to human senses, but chronographs/chronometers are
| a heck of a lot cheaper than a super-slow-motion camera.
|
| Commonly used for people testing out different combinations of
| things for long range precision target shooting.
|
| https://www.snipercountry.com/best-shooting-chronograph-revi...
| AustinDev wrote:
| They clocked the glass at ~3,000 mph so it'd be a lot closer
| with 5.56 being ~2,000 mph. The fastest production bullet I
| believe is .270 Swift which is over 4,000 fps depending on
| barrel and conditions.
| vidanay wrote:
| Pick consistent units!
| walrus01 wrote:
| Getting Americans to not use measurements like grains (for
| powder loads or bullet weights), feet per second, yards,
| MOA, cartridge dimensions and chamber dimensions and barrel
| sizes in inch-based measurements and other non-metric
| measurements for anything rifle related is unlikely to
| happen anytime soon. Unfortunately.
|
| Even things which happen in supposedly entirely metric
| countries in Europe/NATO land use USA-spec things. Such as:
| Oh, you want to replace a barrel on your M4 rifle used by a
| European military? Time to get out your _half inch_ square-
| drive socket torque wrench and torque that barrel to a
| certain value in _foot-pounds_... And after you 're done
| you get to mess around with your SAE spec hex key set to
| reinstall the hand guard and associated stuff. I'm not
| kidding.
| bell-cot wrote:
| Vs. those darn limeys, where you just have to know that a
| QF 17-pounder is a WW _II_ anti-tank gun, but a QF
| 18-pounder is a WW _I_ field artillery piece...
| permo-w wrote:
| > like grains (for powder loads or bullet weights)
|
| or heroin
| vidanay wrote:
| I was referring to the use of MPH (which is probably
| wrong) and FPS mixed together.
|
| I don't care about bullet caliber being mixed mm and inch
| - I consider them to just be "a size" and not a
| measurement.
| LarryMullins wrote:
| > _I consider them to just be "a size" and not a
| measurement._
|
| You're right to consider it that way. In many cases,
| bullets aren't actually the size the name would suggest.
| For instance, .380 ACP is actually .355 inches (9mm) in
| diameter. 5.56x45mm is actually 5.7mm.
| rootusrootus wrote:
| Isn't it just a straight 1:1 calculation in either case?
| 1 mph === 1.46667 fps
| kmonsen wrote:
| 4000 fps ~= 2800 mph
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(page generated 2022-12-16 23:00 UTC)