Axxman300
Philosopher
Cars do float for a while. And all vessels will sink when they capsize.
The sinking of MS Estonia: Case Reopened Part VII
- Thread starter Jack by the hedge
- Start date
-
- Tags
- ms estonia
Andy_Ross
Penultimate Amazing
- Joined
- Jun 2, 2010
- Messages
- 67,722
Maybe Mick or Keith.
P.J. Denyer
Penultimate Amazing
Well it does depend on what planet you're on...
wollery
Protected by Samurai Hedgehogs!
- Joined
- Feb 27, 2003
- Messages
- 11,308
Technically speaking, yes, but certainly not in the way Vixen meant it.
JayUtah
Penultimate Amazing
Yes, you're on the right track. I'm engaged in a Socratic exercise with @Vixen for as long as she will cooperate. And I promise we'll get to all the applicable factors as they become significant. But for now I'm trying to excise away all of Vixen's irrelevancies and misconceptions to get at the core physics. And while I appreciate the group effort, topics like impact with water just muddy up, well, the water.
The important takeaway at this point is exactly what you say above: An object of mass m traveling underwater at velocity v will collide with barrier with exactly the same energy as an object of the same mass moving through a vacuum at velocity v and striking the same barrier. You can be traveling through molasses at velocity v and the collision mechanics will be the same. If I tell you the mass of the vehicle and the velocity at impact, it doesn't matter how that velocity was achieved.
theprestige
Penultimate Amazing
We all know you're wrong and flailing whenever you resort to dialect.
Axxman300
Philosopher
I wonder if he knew Dick Cheney?
Axxman300
Philosopher
Why is the paint ONLY scraped off around the rupture? Why is the paint scraped off at all? I ask because the only places the paint in scraped off on the wreck in here. It this was on land there would be paint scrapings on the rocks too.
And why are there no breaches where the ship landed on the mud? Why just the rocks?
You're awesome with numbers, what are the odds that the whole breach, allegedly made on the surface, would perfectly align with the rocks on the sea floor when it sank?
Axxman300
Philosopher
I just don't see a submarine captain saying, "Don't worry about hitting anything at this depth". And all the sea charts in history evolved out of NOT hitting anything. Not hitting anything is the second component of navigation (I think).
junkshop
Otto's Favourite
Please just stop this silliness. It is obvious that at some point you confused 'kemosabe' and 'savvy'. That you refuse to acknowledge that is sad. What makes it worse is that 'savvy', the slang term whose meaning you insist on attributing to 'kemosabe', isn't even cockney rhyming slang: it entered English from French and/or Spanish via West Indian pidgin.
Last edited:
P.J. Denyer
Penultimate Amazing
Unwin was born in Pretoria, so a little outside the catchment area....
Or my nephew Paul.
JayUtah
Penultimate Amazing
It's not something that requires her notion of consideration in the collision mechanics. This is where lay people commonly run afoul of basic physics because it's a counterintuitive principle. Gravity does participate in the problem in the vertical case: it's the "how" for velocity—that's all. Just like a jet engine, a diesel motor, or a donkey might be the "how" in the horizontal case—we don't change the collision mechanics from donkey to rocket. It's irrelevant "how" we got to v. If we know the value of v, we don't care how we got there. Consequently we don't think differently when gravity is the "how."
Congruently, it doesn't matter what hardships the object may have endured while getting to v at the instant of collision. It could be breezing along in air, zipping through a vacuum, or wading through molasses. If the balance of physical effects—both motive and resistive—arrive at a velocity of v, that's all we need to know or care about.
If I hoist a car of mass m by its rear until its front bumper is 5.1 meters above a concrete slab, a property of gravitational potential energy now pertains to the car. Gravitational potential energy PEg is determined by the mass of the car, the height above some reference point (the concrete slab), and the strength of gravity on the planet in question. We'll confine our discussion to Earth, hence:
where g is Earth's value of 9.81 m/s2. For the mass of the car, just let m be m for now. In order to reason about collision mechanics, we have to know kinetic energy, KE. That value matters oodles more than anything you could know or imagine about a collision. It's the elephant-in-the-room in all the parameters that might follow.
Newtonian physics describes a process whereby gravitational potential energy is converted to kinetic energy. The technical term for it is "falling." Because energy must be preserved in such a system, the kinetic energy that results after a fall of h meters must be equivalent to the gravitational potential energy at that same height h. The general formulation of kinetic energy is
Since energy is preserved,
Mass cancels, which is why we let m be m all along.
We pause to give thanks to Galileo for that flash of insight, and because he also had to endure simpletons and smug busybodies. Solving for v gives
and with the appropriate substitutions,
But all this simply proves that a nominal object (of any mass) dropped in air from 5.1 meters will strike the ground at 10 m/s. Hardly remarkable. But we use the energy formulation on purpose, even though shorter methods exist for determining velocity at the end of a fall. A car of mass m starts with a gravitational potential energy
and arrives at the concrete slab with an equivalent resulting kinetic energy of
The units are noncanonical because we do not resolve mass. This is the same answer as our horizontal examples—but here we have looked more closely at the "how." To save Vixen from any further floundering, this is how gravity is accounted for in the vertical case. It blesses us by converting gravitational potential energy to kinetic energy—the thing that's dispositive in collision mechanics—and thus expended ceases to be of any significant influence. It doesn't linger on as some magical property that makes vertical collisions different from horizontal collisions.
Last edited:
Steve
Penultimate Amazing
Unless Pretoria has their very own Bow Bells.
JayUtah
Penultimate Amazing
It's very important for ship captains not to hit anything. Shell plating is surprisingly fragile. You mentioned a speed of 70 mph in the context of an object striking the surface of the water. You're not wrong about what happens in that case, but it's not very relevant to understanding the kinds of collision we're dealing with here.
SS Park Victory struck the rocks near Finland at an unknown speed. However, the reports indicate she was dragging her anchor in a strong gale at the time. This will naturally limit her speed. Further, the more extensive reports indicate she was battered repeatedly against the rocks by wind and waves. That's not quite the same scenario as a single strike.
Similarly, MS Costa Concordia struck the rocks near Gigli, Italy at 16 knots. That was enough to puncture her hull. And of course she was moving through the water at the time, dealing with water resistance at least as it affected the underwater portion of the hull.
16 kts is on the order of 8 m/s. The reference speed in our car example comes out to about 20 kts. Intuitively we can quite easily say that a ship that hits a rock while going 20 kts won't suprise anyone by suffering a hull breach. @Andy_Ross has posted a number of photographs of ships that suffered fractures in hull plating under normal operating speeds and water conditions.
Now that we have shown that vertical and horizontal collisions result in the same kinetic energy (although arrived at by different means) we can equate horizontal collisions between ships and rocks with vertical collisions between ships and rocks. All we need to know is the kinetic energy at the point of collision in order to continue our reasoning. The next exciting chapter will be whether a vertical velocity of 8 m/s makes sense for a sinking ship.
W.D.Clinger
Philosopher
@Vixen told us the image was produced by the University of Edinburgh, which is false.
As @JesseCuster says, the underlying image came from the University of Strathclyde, but someone else added the text and arrows to obtain the image displayed at Björkman's site and copied (bit for bit) by @Vixen.
@Vixen fails to understand that the University of Edinburgh is not the same as the University of Strathclyde. Adding to that failure, she introduces the topic of intellectual property, getting that topic completely wrong as well.
Yep. The image @Vixen copied into her post at ISF came from Björkman's web site. She lied about that.
Seeking to distract from her multiple failures, @Vixen continues to pretend the topic is her astounding ignorance of IP law.
Dishonest or truly abysmal reading comprehension? No one can rule those out, but I'm guessing it's a Simonton gap.
Yes, the underlying image was clearly credited to Strathclyde University, which explains why a certain variety of triple niner (99.9% of the world would never make such mistakes) would attribute it to the University of Edinburgh, while completely ignoring the fact that the text and arrows were added by Björkman, as part of @Vixen's pathetic attempt to deny the fact that she copied the image (bit for bit) from Björkman's web site.
Next thing you know, @Vixen will be telling us Ipswich is a palindrome for Bolton. I agree with Praline: "This is getting too silly." If Graham Chapman were still alive, he'd order a stop to this comedy sketch.
Last edited:
Vixen
Penultimate Amazing
Being dropped from a height.
Vixen
Penultimate Amazing
East end cockneys didn't stay put in the East End. Half my City work colleagues commuting in from Essex and Kent were true cockneys.
Mojo
Mostly harmless
Can I politely urge you to listen? You claim that the JAIC said that the Estonia floated on a 90° list. You have been asked to cite and quote, and if possible link to, the JAIC saying this. For some reason you are unable to do this, and keep citing things other than the JAIC in an attempt to support your claim.
You claim that the video is "based on the JAIC report". Please cite and quote the section or sections of the JAIC report that support the claim about the Estonia floating on a 90° list is based on.
You have claimed that the JAIC said that the Estonia floated on a 90° list in a "technical report and press release (94/95)". You have also cited a "press release given out by Meister, Lehtola and Forssberg after the Oct 17th meeting in 1994", but the passage you quoted from it doesn't support the claim, it says that "after the vessel had turned over to almost 90° starboard list" it started to sink.
Please provide accurate citations for the report and press release so they can be identified, and quote the passages that support your claim. If possible please provide links to them.
This really shouldn't be difficult. Unless, of course, your claims are untrue.
Last edited:
Mojo
Mostly harmless
Then how do you "know it was drawn by Edinburgh Uni", as you have claimed?