Water as unyielding as concrete

So are you contending that a bullet is incompressable?

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Oh well done. Strawman.
Not what I said.

Although it's beside the point:
Now explain the difference between compressing and breaking up.
You do know there's difference right?
You do realise that compressing the bullet will absorb energy and mitigate the impact?

And again:

Think about this also: how soon after the nose hits the water will the rest of the bullet enter? How much time will there be for friction to take effect?
Given that, on a streamlined object in a fluid medium, it's going to be a relatively minor consideration compared to the all the other forces in play.

 

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Nice uniform compression would do just that: absorb energy.

But uniform compression is not what happens. The bullet is not 100% uniform in construction. Stresses develop where there are microdifferences, contaminations, etc, and portions shear off in differing directions: the beginning of a splat. If the compression even started off being uniform, it soon is not and the breaking up occurs.

 

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I think this is an interesting question.

What's your "Personell Qualifications & Evaluations" credential?

And how will my answer affect the Physics?

 

I just thought of another factor.

For an object penetrating the water there's the object-water friction, then the water-water friction, and now I want to include the lead-lead friction that occurs in a splatting bullet, mid-splat.


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It's easy to do some simple experiments with friction to see that it increases with the square of the velocity. Heck! I thought EVERYONE knew that!


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For some people who can’t stand it, this would be the wrong suggestion, but Wikipedia is getting better...

If you Google “friction square velocity” you’ll see plenty of highly credentialed sources explaining it. Wikipedia is one of them.

 

Correct.

Error alert!
"Uniform compression" is not synonymous with "compression of a uniformly-constructed object".

And you're still hand-waving vigorously....

When a bullet is fired you do know (I'm assuming here) that it starts at zero velocity and is accelerated down the barrel? And that it encounters the lands of the barrel after it exits the cartridge? How much friction do you think those lands impose on the bullet? More? or less? than travelling through water? Does it break up in the barrel?

I note that three times now you ignored my question about your engineering experience. Am I to take that you have none? That you're wildly guessing here because it's an answer you like?

Why bother repeating something that's already been addressed (and something that you have contradicted and ignored questions on)?

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So interesting that you've ignored it 3 times?

WTF is a "Personnel Qualifications and Evaluation credential"?

You can't think how it would affect the physics?
Engineering is studied so that one knows where, when and how to apply physics to a problem -

Heck! I thought EVERYONE knew that!

 

Well....

...could we try soaking the bullet in WD-40 and see if it doesn't break up?

 

Uh, yes. And your point here would be... what, exactly?
I have already been through this - post #73 - re-read the final comment in that post.

 

Please allow me to try another approach, reversing the order.
Let’s start with friction and work towards the unyielding surface of water.


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Have you ever noticed while walking on a soft-sand beach how it can be pretty difficult? Waring shoes on soft sand masks this a bit, like using snowshoes in the cold stuff. But barefoot you tend to sink in a bit, so it makes walking pretty sloggy.

But what happens if you start running? The vertical velocity of foot to sand increases. Let’s see how this affects things.

For low velocities (walking) one foot sinks deep into the sand there’s a lot of friction. The friction going down prevents you from “pushing off” efficiently for the other foot’s next step and some effort is wasted in this friction. Then the friction going up takes additional effort.

But when you run that friction going down is MUCH higher and you don’t sink as much.

Summing it up:

It takes much less energy to run than to walk.
You don’t sink as deep in the sand running.
When you run the soft sand FEELS harder.

The sand feels more like an unyielding surface when you run.

Try it.

 

So let's see...

We got water.

We got sand.

All we need now is limestone and we got concrete.

 

Um, false.
The extra effort is required to lift your foot out of the depression, or to move aside the sand as you kick through the depression.

You don't sink as much because you're not giving the sand time to collapse under your foot before moving on.

Really? I think you need some basic science courses.

Already explained.

And in fact, since your foot is moving faster when running (and impacting faster) by your "logic" you should be encountering more friction from the sand.

Logic. It's a bitch, huh?

 

Does that mean you don't need to do the experiment and try running on soft sand?

 

A) what makes you think I haven't?
B) what makes you think your interpretation of the "experiment" is correct? (Did you actually take measurements or are you just guessing wildly about what happens and why?)
C) regardless of the result your claim about sand directly contradicts your claim about bullets in water - one of them (or both) has to be wrong.

 

The fact that it wasn’t you who brought up the soft-sand running as another example of an unyielding surface that’s velocity sensitive.

If you had done this experiment you’d have remembered it. The results are dramatic.

One time I was very fatigued and had to walk a long distance on the sand. Since the square of the velocity being a major player in friction was SO FUNDAMENTAL to my background, it occured to me during this tiring trek that maybe it would be easier if I ran. It was.

I think you missed the fact that I was only talking about the vertical component of foot velocity, not the horizontal velocity. The horizontal friction (mostly due to air) is extremely low and negligible here.

But if horizontal friction was not so low, then you would be somewhat correct and I would have to include that in the mix. But the POINT was the unyielding surface to vertical motion, so I ignored horizontal friction.

 

So bringing up (or not bringing up) one single example is evidence that I haven't actually done it?
Wow.
Where did you learn to reason? (If you actually did so).

Bearing in mind that I live (and have lived all my life) about 40 miles from the coast and every single year our holiday while children was at the seaside would you like to take another guess?

And, one more time. If you're running your foot is moving faster than if you're walking. Therefore, (again by your own argument) a running foot will suffer more friction than walking one.
So, this "square of velocity being fundamental to your background" would you care to tell me how? And why (and how) you got it wrong in an earlier post? And why you persist in misapplying it? All you've done so far is hand-wave and make erroneous claims and comparisons.

Running tends to lift the higher than walking. And since you cover ground faster then the vertical velocity is greater than when walking. Keep trying (or rather, don't keep trying: go away, get an education and then try).

And once again you are misapplying physics. You've assumed too many things, ignored reality and hand-waved. Again.

 

Water is a somewhat unyielding surface to an athlete performing the most astonishing feat of barefoot water skiiing.

When I was in high school I went water skiing hundreds of times, and saw the effects of velocity on the unforgiving nature of water. When shooting from one far side of the wake to the other the one skiing is going quite a bit faster that the boat. The boat is traveling straight ahead, but the one water skiing like this is traveling along a diagonal and covering a lot more distance. Falling at this high speed is like falling off a skateboard on asphalt, minus the blood. The water feels hard.

But for all the water skiiing I did, barefoot skiing was beyond my athletic ability, WAY beyond it. I’ve been told that you need to go 55 mph to barefoot ski. That’s very fast on water. They have to lean way back to form an upward pointing planing surface at the soles of their feet. It’s a big deal not only for balance but also for strength.

I’d love to hear from a Physics oriented person who has done barefoot water skiing. I wonder what it feels like to do it? And what is it like to fall at 55 mph on the water?

 

Irrelevant to topic and containing false information.
Take your own advice and try Wiki.

 

We make a good team.

I do the Physics and you do the ad hominem to make it more entertaining.

 

And another two errors.
1) you haven't done any physics. At least not in this thread.
2) I haven't done any ad homs.

But well done anyway.

 

Maybe we could make a U-Tube video.

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