Little* Things that Puzzle the Hell Out of You (*or big)

[chrLz]

How about a thread on things that, despite there being accepted explanations, still just don't seem right or possible...

Here's mine.

Boat wakes...



Now some of you may know I have a bit of a marine background, but it *isn't* in fluid dynamics.. so my knowledge of just how the wake concept works is a bit.. shallow. (Geddit!?)

But I always wonder in awe, as I watch a little boat putter by in a calm marina, and then watch the multiple wavefronts spread out behind it, for hundreds (if not thousands) of metres, and also watch those same waves gently but firmly lift up huge pontoons, seemingly expending enormous amounts of energy as they get moved up and down... And all that power/energy came from a tiny chunk of aluminium, powered by a 5 horse Evinrude..???? Nah, not possible.

Actually, I do sorta understand the mechanics of it all, but it just looks *wrong*!!! Does anyone know how to explain it all, but in a way that my subconscious, rather than my conscious, will finally accept?

Oh, and for those who need a picture, scroll down to the bottom of this page....
http://www.egamiimage.ca/home.html
As it's a cool shot imo, I hope no-one minds me giving his website a free plug..!



Oh, and I also have a big problem with the much loved concept of infinity, but I shall leave that for another day...
∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞

[m0r1arty]

I'll have a go, an educated go, but a go nonetheless.

When your boat cuts through the water it separates an equilibrium that was resting against itself (albeit the whole thing is constantly moving). The water your push to the left and right (port and starboard for the Yar-Yars) now rests upon other water, which was resting on it beforehand. This causes that water to push down upon the water that it was resting upon and so on and so forth. This causes a snowball effect which goes on (in essence forever) until the original segment cut by your haul 'heals' and lets water rest in equilibrium again pulling back in all additional forces which causes the wake to subside.

How's that for a go at it?

-m0r

[chrLz]

I'll have a go, an educated go, but a go nonetheless.

When your boat cuts through the water it separates an equilibrium that was resting against itself (albeit the whole thing is constantly moving). The water your push to the left and right (port and starboard for the Yar-Yars) now rests upon other water, which was resting on it beforehand. This causes that water to push down upon the water that it was resting upon and so on and so forth. This causes a snowball effect which goes on (in essence forever) until the original segment cut by your haul 'heals' and lets water rest in equilibrium again pulling back in all additional forces which causes the wake to subside.

How's that for a go at it?

-m0r

Nice... but.. my brain hurts!!!

[RICH-ENGLAND]

its not a real lot different to the movement of air and the shockwave that builds at the nose of a plane and the vortex's at the rear.

hence why nasa uses some liquid tanks for aerodynamic testing as its much like a wind tunnel but you can see the flow in streams of dye.

thanks

rich

[Access Denied]

And all that power/energy came from a tiny chunk of aluminium, powered by a 5 horse Evinrude..???? Nah, not possible.

Well, just picture 5 actual horses pulling it.

Actually, I do sorta understand the mechanics of it all, but it just looks *wrong*!!! Does anyone know how to explain it all, but in a way that my subconscious, rather than my conscious, will finally accept?

I take it this isn’t working for you…

http://en.wikipedia.org/wiki/Wake

In incompressible fluids (liquids) such as water, a bow wake is created when a watercraft moves through the medium; as the medium cannot be compressed, it must be displaced instead, resulting in a wave. As with all wave forms, it spreads outward from the source until its energy is overcome or lost, usually by friction or dispersion.

How about Newton’s laws then? You know, for every action there is an equal but opposite reaction and the first law, every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it? Picture the domino effect with water molecules as the dominos…

http://en.wikipedia.org/wiki/Domino_effect

No?

Anyway, that was a cool shot. I like this one too from the wiki page above…

[chrLz]

And all that power/energy came from a tiny chunk of aluminium, powered by a 5 horse Evinrude..???? Nah, not possible.

Well, just picture 5 actual horses pulling it. ...

Ah, now we're onto something.. DRAUGHT horses.. Yes....

Like I said, it just doesn't seem to add up in my head. A little boat goes past, and then i can watch a pontoon weighing possibly a ton, being lifted, then dropped, lifted then dropped, several times as the wake passes beneath. If it was *me* doing that lifting, I couldn't even lift it once. But I could easily toss that little boat onto a roof rack, and probably lift the guy piloting it as well. So, there's just no way for my head to believe it is possible. Ergo, it's obvious - free energy is being created.

Hey... I feel a Youtube video coming on, and I can sell the plans, and ...

[Slippery Jim]

Black holes and the Big Bang.

If black holes are formed when a star reaches a critical mass, how come when all the mass in the universe was concentrated in a tiny point at the moment of the Big Bang, did the entire universe simply not collapse in on itself into a super-massive black hole?

I really, really can't get my head around this.

Someone please enlighten me!

[Access Denied]

A little boat goes past, and then i can watch a pontoon weighing possibly a ton, being lifted, then dropped, lifted then dropped, several times as the wake passes beneath.

Ah, the plot thickens. I see what you mean, that does seem counterintuitive. Speaking of, I got all three of these wrong…

Buoyancy Brainteasers
http://www.pbs.org/wgbh/nova/lasalle/buoyancy.html

Ever notice how relatively easy it is to push a relatively large boat away from a dock?

Important Safety Tip: Be careful when pulling a relatively large boat toward a dock.

[don’t ask]

I think that may have something to do with it…


A hot air balloon when it has neutral buoyancy has no weight for the men to support but still retains its great mass and inertia.

http://en.wikipedia.org/wiki/Mass_versu ... and_weight

The effects of buoyancy doesn’t just affect balloons; both liquids and gases are fluids in the physical sciences, and when all macro‑size objects larger than dust particles are immersed in fluids on Earth, they have some degree of buoyancy. In the case of either a swimmer floating in a pool or a balloon floating in air, buoyancy can fully counter the gravitational weight of the of the object being weighed.

The mass of weightless (neutrally buoyant) balloons can be better appreciated with much larger, hot air balloons. Although no effort is required to counter their weight when they are hovering over the ground (when they can often be within one hundred newtons of zero weight), the inertia associated with their appreciable mass of several hundred kilograms or more can knock fully grown men off their feet when the balloon’s basket is moving horizontally over the ground.

Buoyancy and the resultant reduction in the downward force of objects being weighed underlies Archimedes' principle.

So there you go, some dude that lived some 2,200 years ago explains why I'm much more cautious around boats now... although in my defense I wasn't a "fully grown man" when I independently discovered this principle.

Ergo, it's obvious - free energy is being created.

Obviously…

http://en.wikipedia.org/wiki/Wave_power

Hey... I feel a Youtube video coming on, and I can sell the plans, and ...

Too late…

Someone please enlighten me!

Is there an echo in here? Or was my attempt just that bad…

[and if that wasn’t bad enough ask in that thread what caused it]

[chrLz]

A little boat goes past, and then i can watch a pontoon weighing possibly a ton, being lifted, then dropped, lifted then dropped, several times as the wake passes beneath.

Ah, the plot thickens. I see what you mean, that does seem counterintuitive. Speaking of, I got all three of these wrong…

Buoyancy Brainteasers
http://www.pbs.org/wgbh/nova/lasalle/buoyancy.html

That second one got me! But I was annoyed with myself, because as I read the answer I realised I just hadn't spent long enough thinking about it... **Spoiler** follows in tiny text.. **Relative density is the key - of course - it's obvious!!!**

Ever notice how relatively easy it is to push a relatively large boat away from a dock?

Heheh. While I've only personally owned smallish craft, one of the very best parts of the very best job I ever had involved looking after a research boat. It was really just a *very* large open speedboat with lots of cool marine-biology-related sciency/sampling gear all over it, and every two weeks or so I would take it out for a run, if it had been idle. I discovered that with great care, I could in fact trailer it down to the local ramp and launch and retrieve it all by myself. If it had been a metre longer, I don't think I would have made it.. But anyway, when you are handling a fairly large boat, in varying conditions, and all you have is.. yourself.. Yep, you learn very quickly, especially about inertia, and the power of relatively small waves/swells as they come into shallow water, especially when combined with interesting side topics like resonances... Thankfully, despite some awkward moments, the boat, the various wharves and ramps I frequented, the trailer and the 4WD all survived my piloting with nothing but a few minor scratches and a bruise or two..

Anyway, I think there is a lot to the topic, and perhaps there is some latent energy being 'stolen' as that little boat pushes and shoves huge pontoons. One day maybe I'll look more deeply into it, although perhaps it is good if there are a few things that my mind cannot grasp...

[Slippery Jim]

Is there an echo in here? Or was my attempt just that bad…

[and if that wasn’t bad enough ask in that thread what caused it]

Doh! I've asked the same question on a few forums and totally forgot I'd asked it here.

It seems mother's Alzheimers is hereditary after all.

I'll go and read the replies now.

[Access Denied]

That second one got me! But I was annoyed with myself, because as I read the answer I realised I just hadn't spent long enough thinking about it...

That’s what I chalked up my 0 for 3 performance to… if I was being graded on it I would have been more careful.

While I've only personally owned smallish craft, one of the very best parts of the very best job I ever had involved looking after a research boat. It was really just a *very* large open speedboat with lots of cool marine-biology-related sciency/sampling gear all over it, and every two weeks or so I would take it out for a run, if it had been idle.

[looks at all the dials and switches and drools]

One day maybe I'll look more deeply into it, although perhaps it is good if there are a few things that my mind cannot grasp...

Especially if it’s going to involve solving some differential equations…