Spinning bullets on a frozen lake...

SteamWake · 10-25-10, 09:06 AM

Okay you physics professors splain this one !

http://www.break.com/index/spinning-...n-lake-1936597

(Video of bullets being shot into a frozen lake and the slug ends up spinning like a top).

AngusJS · 10-25-10, 09:32 AM

The bullet is showing the same spin that it would have while in the air (i.e. along the same axis). I guess it bounced off the ice, landed again, and then maybe its heat melted the ice around it, which provided lubrication that let it spin for so long? I'm not a physics prof, though.

I'm just amazed that those guys weren't hit by ricochets - that bullet ended up behind them, just off to the left, after all.

SteamWake · 10-25-10, 09:43 AM

Ever seen that video of a guy firing a 50 cal into a piece of metal, the slug comes rocketing back and nearly takes the guys ear off

Dowly · 10-25-10, 09:48 AM

Quote:

Originally Posted by SteamWake

Ever seen that video of a guy firing a 50 cal into a piece of metal, the slug comes rocketing back and nearly takes the guys ear off

Schroeder · 10-25-10, 10:01 AM

The barrels of guns are designed to force bullets into a spin when they are fired through them. This stabilizes the bullet in flight and makes the weapon more accurate.http://en.wikipedia.org/wiki/Rifling

Jimbuna · 10-25-10, 10:25 AM

Add the fact that there will be next to no friction/resistance to the spinning attitude of the bullet because the ground is actually ice.

SteamWake · 10-25-10, 10:43 AM

You would think that smacking into the ice would take alot of that momentum out of the slug on all axis.

Also I dont understand why the slugs did not flatten upon hitting the ice.

Penguin · 10-25-10, 10:46 AM

I also cannot explain it, so far I regard Angus' explaination as the most reasonable one. Some observations:
- The bullet spin is definitely clockwise. Can any of you gun nuts identify the firearm and confirm that the barrell of this model provides a clockwise spin?
- Each shot makes an impact onto the ice, however the bullet most likely bounces back when it is fired in a certain angle. This angle should be rather flat < 45°, otherwise the projectile would penetrate into the ice.
- I guess the little wall of frozen ice and snow, where the targets are located, has something to do with it. The bullet gets reflected back towards the shoote/camera guy. So there must at least 2 reflections.
- The colder the ice gets, the harder it is. I read somewhere, when the temperature reach -25° C, the hardness of ice would be the same as steel. There are no deformations visible, as I would have expected when a projectile gets reflected by a hard surface. So either it was not that cold, or the energy of the bullet melted the ice on the impact point enough to provide a "smooth" bouncing.

Another good argument for free firearms for all, so we can all recreate this little experiment in the winter!

tater · 10-25-10, 10:57 AM

FMJ from a pistol doesn't deform very much. I shoot into dirt berms and pull out perfect bullets all the time. The video is entirely unsurprising to me.

The bullet was effectively stopped by the ice (minor ricochet). This is a conservation of momentum issue, with the momentum transferred to the ice. The spin is a conservation of angular momentum issue. There isn't much acting on the bullet to stop the spin, so it spins.

Not surprising at all.

gimpy117 · 10-25-10, 02:04 PM

but dirt is loose...Ice is solid...I think it would deform

10-25-10, 09:06 AM	#1
SteamWake Rear Admiral Join Date: Mar 2005 Posts: 13,224 Downloads: 5 Uploads: 0	Spinning bullets on a frozen lake... Okay you physics professors splain this one ! http://www.break.com/index/spinning-...n-lake-1936597 (Video of bullets being shot into a frozen lake and the slug ends up spinning like a top). __________________ Follow the progress of Mr. Mulligan : http://www.subsim.com/radioroom/showthread.php?t=147648

10-25-10, 09:43 AM	#3
SteamWake Rear Admiral Join Date: Mar 2005 Posts: 13,224 Downloads: 5 Uploads: 0	Ever seen that video of a guy firing a 50 cal into a piece of metal, the slug comes rocketing back and nearly takes the guys ear off __________________ Follow the progress of Mr. Mulligan : http://www.subsim.com/radioroom/showthread.php?t=147648

10-25-10, 10:01 AM	#5
Schroeder Navy Seal Join Date: Apr 2008 Location: Banana Republic of Germany Posts: 6,170 Downloads: 62 Uploads: 0	The barrels of guns are designed to force bullets into a spin when they are fired through them. This stabilizes the bullet in flight and makes the weapon more accurate.http://en.wikipedia.org/wiki/Rifling __________________ Putting Germ back into Germany.

10-25-10, 10:25 AM	#6
Jimbuna Chief of the Boat Join Date: Feb 2006 Location: 250 metres below the surface Posts: 190,473 Downloads: 63 Uploads: 13	Add the fact that there will be next to no friction/resistance to the spinning attitude of the bullet because the ground is actually ice. __________________ Wise men speak because they have something to say; Fools because they have to say something. Oh my God, not again!!

10-25-10, 10:43 AM	#7
SteamWake Rear Admiral Join Date: Mar 2005 Posts: 13,224 Downloads: 5 Uploads: 0	You would think that smacking into the ice would take alot of that momentum out of the slug on all axis. Also I dont understand why the slugs did not flatten upon hitting the ice. __________________ Follow the progress of Mr. Mulligan : http://www.subsim.com/radioroom/showthread.php?t=147648

10-25-10, 09:32 AM	#2
AngusJS Seasoned Skipper Join Date: Jan 2002 Posts: 746 Downloads: 62 Uploads: 0	The bullet is showing the same spin that it would have while in the air (i.e. along the same axis). I guess it bounced off the ice, landed again, and then maybe its heat melted the ice around it, which provided lubrication that let it spin for so long? I'm not a physics prof, though. I'm just amazed that those guys weren't hit by ricochets - that bullet ended up behind them, just off to the left, after all.

10-25-10, 10:46 AM	#8
Penguin Ocean Warrior Join Date: Mar 2010 Location: Rheinische Republik Posts: 3,322 Downloads: 92 Uploads: 0	I also cannot explain it, so far I regard Angus' explaination as the most reasonable one. Some observations: - The bullet spin is definitely clockwise. Can any of you gun nuts identify the firearm and confirm that the barrell of this model provides a clockwise spin? - Each shot makes an impact onto the ice, however the bullet most likely bounces back when it is fired in a certain angle. This angle should be rather flat < 45°, otherwise the projectile would penetrate into the ice. - I guess the little wall of frozen ice and snow, where the targets are located, has something to do with it. The bullet gets reflected back towards the shoote/camera guy. So there must at least 2 reflections. - The colder the ice gets, the harder it is. I read somewhere, when the temperature reach -25° C, the hardness of ice would be the same as steel. There are no deformations visible, as I would have expected when a projectile gets reflected by a hard surface. So either it was not that cold, or the energy of the bullet melted the ice on the impact point enough to provide a "smooth" bouncing. Another good argument for free firearms for all, so we can all recreate this little experiment in the winter!

10-25-10, 10:57 AM	#9
tater Navy Seal Join Date: Mar 2007 Location: New Mexico, USA Posts: 9,023 Downloads: 8 Uploads: 2	FMJ from a pistol doesn't deform very much. I shoot into dirt berms and pull out perfect bullets all the time. The video is entirely unsurprising to me. The bullet was effectively stopped by the ice (minor ricochet). This is a conservation of momentum issue, with the momentum transferred to the ice. The spin is a conservation of angular momentum issue. There isn't much acting on the bullet to stop the spin, so it spins. Not surprising at all.

10-25-10, 02:04 PM	#10
gimpy117 Ocean Warrior Join Date: Jul 2007 Location: Kalamazoo, MI Posts: 3,243 Downloads: 108 Uploads: 0	but dirt is loose...Ice is solid...I think it would deform __________________ Member of the Subsim Zombie Army