Why don't knives work underwater?

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

Btfo

knive thoery btfo

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

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

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

this

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.

youtu.be/usZ8MQzbglk

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.

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.

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

lunatic knife theoriests

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

youtube.com/watch?v=7AmLaPD9vwU

Proof that knifes don't work under water.

is a new meme

google it

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

there ya go, yet another proof supporting knife theory

lmgtfy.com/?q=knife+theory

Certainly.

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.

Teeth are for chewing not cutting

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

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

underwater magician

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

because theres not enough oxygen

Why don't brains work on Veeky Forums?

is this a bait thread?

what the fuck

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.

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

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

Because most fish chew their food thoroughly?

They should work better.

Buoyancy.

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

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.

Get out nigger

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.

> 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.

Everything is hypothetical until you apply it to yourself.

nug

some kind of homeopathic knives?

>knives don't cut underwater

added to the stupid dog meme just for you

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

Clearly a pussy.

How do sharks do it then?

Yeah man it was easy.

>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

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.

>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 Veeky Forums, 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?

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

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

>it cuts
>"biased"
wew lad