Water as unyielding as concrete

Er, would they be pistol bullets? I.e. subsonic/ transonic?

http://kwc.org/mythbusters/2005/07/mythbusters_bulletproof_water.html

It does, of course, depend on which bullet and what velocity (and possibly tip shape/ bullet form).

 

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In the interim, it seems as though that involve after the projectile enters the water. It is my understanding you meant hitting the surface with op. also, the difference between speed and force speed

 

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In the interim, it seems as though that involve after the projectile enters the water. It is my understanding you meant hitting the surface with op. also, the difference between speed and force speed comes into play after impact.

 

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So bad you posted twice?

Could you please translate this into English?

WTF is "force speed"?

 

Pistol

Next time I'm trying to out swim bullets I'll hope they are rifles firing at me, at least until I need to come up for air.

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I would agree with Dyw... and then add that it’s friction (sensitive to velocity squared) that makes it hard for water to “move out of the way.”

 

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I had no concept before this of bullets having vastly different speeds. Now I realize the answer was already there in Asguard' s post.

This has been a very enlightening thread. Thank you to all who contributed!
Special thanks for bringing up the existence of the 'bulk modulus' and the 'shear modulus' Dyw. although I will prob never use them it gives me some kind of autistic pleasure just knowing they are there

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i like to thank whateverthefuckhisnameis for that gem
absolutely brilliant!

 

I just saw the Myth Busters episode about running on water.

In almost every instance where velocity was mentioned, it was horizontal velocity components and not vertical. All increases in velocity were in the horizontal action. And, the vertical velocities were roughly the same for all the setups.

At one point only do they allude to the vertical components of velocity regarding the slapping actions of the lizard that does successfully run on water. Looking close, a whip-like action seems to be involved.

 

I suspect the surface tension aspect of water comes into play here and probably some math could determine how much horizontal speed is needed to keep any given weight of an animal from sinking before the next step could be taken.

It would probably show that for anything bigger than the lizard the horizontal speed needed would become unmanageable.

 

I can't help but think that there's some confusion that could be avoided if the different levels involved here were sorted out.

The bottom level approach would look at atom clusters hitting atom clusters, and then the clusters would be extrapolated to a macroscopic object (airplane) and liquid surface (ocean). Lots of bookkeeping to do here.

Surface tension and friction are higher level approaches that greatly simplify the bookkeeping at the expense of microscopic exactness. It’s the neat correspondence of such an abbreviation to bottom level reality that allows us to use it.

Surface tension is useful for reducing the complexity of a 3 dimensional liquid to a 2 dimensional stretchy surface, like a trampoline. By stretchy, I mean it exhibits a Hooke's Law linear force.

But all that abbreviation’s correspondence to bottom level reality breaks down when the "surface" is penetrated and destroyed. The linear stretchiness only works within a certain window. Trampoline actions don't work well if a huge rock is placed a few inches below it.

Surface tension may work well for the extremely early moments of impact, but it soon must yield to some other high level abbreviation (hint: friction) or a retreat to the bottom level of atomic collisions is required.

 

From your post, I'd bet the farm you haven't read much of this thread. You really should, it's very interesting.

 

Well look at it this way: Ever see bugs walk on water or small animals walk on water? They are obviously walking on something and that something is enough to hold their weight...it is solid.

 

Its not a good example to use. A better example is dropping an egg from two inches above water and dropping an egg from a few hundred feet. One will definitely break. The egg is free falling without any external forces, the bullet is being forced, same as if you simply dropped the bullet instead if firing it.

 

Surface tension. It's not "solid". Try to learn something before posting.

 

Utter nonsense. The greater the height the higher the velocity: therefore it's comparable.
A bullet isn't "forced".
And I'm still waiting for you to explain what you think "force speed" is; post #123.

 

Oh...man listen to this child.

If i drop an small round ball of steel shot onto glass it may or may not break the glass. Depends on the thickness of the glass. So i drop the shot on the glass from six feet away and it does not break or....i shoot the shot out of a canon from six feet away. Now will it break the glass? Which one has the greater chance of breaking the glass? Should be obvious.

 

What is your point here?
That it's dependant on the impact velocity?
Oh, wait, just what I've been pointing out all along...

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Not to long ago the science channels Bug Wars series talked about water skates and water spiders. The hairs on their feet helps spread the very slight weight of the bugs over a greater area which allows the surface tension of the water to keep them from sinking. However surface tension is not the reason why water sometimes acts as though it's very hard. Please see earlier postings.

 

But the part of their bodies, whatever that turns out to be, is still making contact with something. Look at a piece of wood floating on water and compare that to trying to float the wood on air and then thick air from smog or smoke. And i never made the claim that water is as unyielding as concrete because that is not true. Even if the cement is still wet it is more dense than water.

Getting back to the wood, it will float on a foot of water, a few inches of water or a few hundred feet, makes no difference.