Why don't knives work underwater?

Density.

the density of the water mass is too great

>>8935554
they do

>>8935580
no they dont, find one video of a knive cutting underwater. the water is too dense (especialy at higher depths) and the knive wont cut

>>8935582
>find one video of a knive cutting underwater
really?

>>8935596
im waiting

[spoiler]test[/spoiler]

>>8935602
https://www.youtube.com/watch?v=y8PuEBVk1wI

>>8935606
fake and gay

idk but i've been making a killing selling dive knives to these morons who think otherwise

>>8935606
Btfo

>>8935606
knive thoery btfo

>>8935606
this is a biased video because its from a company trying to sell the knive. of course they want you to believe knives can cut underwater

>>8935554
This guy doesn't know what the hell he's doing. You're supposed to stretch the rope taut when you're trying to cut it.

That's a very good question.

Because the density of water is about 1000 times the density of dry air you need to exert 1000 times the force to move the knife.

Also, because of the no slip condition you will always be cutting a fluid with zero velocity, zero as in not moving. You physically cannot cut a rope underwater

>>8935606
This is clearly evidence that knives cant cut through water, hes just ripping the rope through force alone, not cutting it. Nice job disproving yourself

You can't cut the rope underwater when you take the bait.

You're just along for the ride

>>8935620
this

>>8935620
By that logic, then fir wood, with a density about half that of water, takes about half the force to move a knife through compared to water. Even so, whittling really isn't that hard, strength-wise. Prepubescent kids are expected to be able to do it.

https://youtu.be/usZ8MQzbglk

>>8935609
This. Diving companies really try hard selling that shit to people even though they know it doesn't work. Its simple physics but they try to cover it up.

>>8935630
yes you can cut wood above water because your only displacing the air around you which is very light.

Knife theory however, simply states that under the pressure of large masses of water (such as the ocean) the knife will not cut because you need to displace the water around you, which in turn requires moving the millions of gallons of water in the ocean.

>>8935631 only works because the amount of water being displaced is very small

>>8935630
lunatic knife theoriests

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>>8935636
>Knife theory however, simply states that
I would like to read this knife theory. Can you give any sources?

https://www.youtube.com/watch?v=7AmLaPD9vwU

Proof that knifes don't work under water.

is a new meme

>>8935641
google it

>>8935554
Well, I guess that explains the lack of sharp teeth in aquatic predators.

>>8935667
there ya go, yet another proof supporting knife theory

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>>8935665
lmgtfy.com/?q=knife+theory

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>>8935668
Certainly.

>>8935606
Why do people have so much trouble cutting rope? Even on land I see people act like god damn retards when trying to cut rope. Just pull the rope really tight and slide the knife edge across it.

>>8935679
Teeth are for chewing not cutting

>>8935679
why are people so afraid of sharks?
the worst they can do is bite your limb (you probably wouldn't pay much attention to pain because of the adrenaline rush)
and while it's latched on, you can just beat the shit out of her

>>8935735
Because rope is designed to be strong and by extension, not cut easily

>>8935606
underwater magician

at 2:41 you can clearly see a second rope up his sleeve (pre cut on land)

>>8935554
because theres not enough oxygen

Why don't brains work on 4chan?

is this a bait thread?

what the fuck

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>>8935554
Only under salt water. The salt dulls the knife almost upon contact. It also react with the rope to strengthen it. And you have to reply to this post or your mother will die in her sleep tonight.

>>8935775
But, it is cut very easily. Just add tension.

I know they don't work underwater but what about high altitude?

>>8935763
Because most fish chew their food thoroughly?

>>8935895
They should work better.

>>8935554
Buoyancy.

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>>8935606
Damn anon, why do you have to just go and ruin the fun like that...

>>8935773
Adult bull sharks can bite with a maximum force equivalent to 6,000N. That's more than enough to snap a persons leg clean off.

>>8935887
Get out nigger

>>8935554
So you can't saw through shit due to increased density but is there anything preventing you from puncturing straight through materials as a way to sever it

Like, I don't understand how underwater predators like sharks are perfectly capable of using their teeth to kill prey but somehow a knife won't cut a rope underwater.

>>8935554
> picture shows a knife doing it's thing underwater

he looks relatively confident that knives work underwater

>all these undergrads ITT who havent done Knife Tomography III yet

Look at them desperately clinging onto their newtonian understandings, I bet they all just assume from pictures that knifes work underwater and have never tried themselves.

>>8936270
Everything is hypothetical until you apply it to yourself.

>>8935887
nug

>>8935609
some kind of homeopathic knives?

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>>8935554
>knives don't cut underwater

added to the stupid dog meme just for you

>>8935773
Have you ever fought off a shark before? You don't sound like someone who has.

>>8937293

Clearly a pussy.

>>8935582
How do sharks do it then?

>>8937293
Yeah man it was easy.

>>8935773
>why are you scared of sharks it's only going to rip off your limbs and then shrug off any hits you try to do to it because its weight is in the quadruple digits and also you're underwater so you can't hit your hardest anyway

>>8935955
That's what you would think, but knife theory has proven that, somewhat counterintuitively cutting at higher altitudes creates a waves of micro-gravitational vacum systems. That's is why knifes are useless at high altitudes with mountaineers opting for high power turpentine cutting torches. Try taking a knife on a real mountain and you'll get laughed off base camp.

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>>8935636
>the knife will not cut because you need to displace the water around you, which in turn requires moving the millions of gallons of water in the ocean.

I don't frequent /sci/, so coming in and seeing all the esoteric board trolling is fun.

So if I try to shoot myself with a gun underwater, will I die?

>>8937507
Not if you start with smaller caliber bullets and build up an immunity first

>>8935998
It's the fourth Google result for (knife cutting underwater), somebody was going to post it eventually.

>>8935614
>it cuts
>"biased"
wew lad