Why do big ships float? [Buoyancy and flotation explained]

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Do you look at enormous ships out at sea and wonder how it is possible that they can float?
This video explains how big ships float, giving an introduction to both buoyancy and flotation.
The basic concept is quite simple. Ships need to displace enough water to counter their own weight. If they weigh more than they displace, they will sink. If they displace the same as they weigh, they will float.
Image of Plimsol Marks - Les Chatfield - CC-BY - creativecommon...
Music from Jukedeck - create your own at jukedeck.com
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[@PeazChess]

I'm still lost but hey, whatever floats ur boat

[@syntheovaldy5173]

😂😂😂

[@KillberZomL4D42494]

You looks like Louis from Left 4 Dead.

[@imm8rtal]

you float my boat bruh

[@gvue4396]

Same, still don't get it

[@ashritsai3744]

Wow superb explanation, thanks a lot, it cleared many of my doubts

[@CasualNavigation]

Thanks Ashrit. Glad it helped

[@antonman1234]

@@CasualNavigation great work

[@Antesdelfinadmin]

You should have been my math, physics or geometry teacher! You'd have made my life so much easier! 👍

[@Therongunner]

I have only ever been on a catamaran for 4 hours as a tourist but, your videos got me interested in shipping. Thank you very much.

[@grondhero]

If I'd known then what I knew now, I would have gone to a maritime college/academy and taken that route. I would love to be an officer on a cargo ship or cruise line. There's a maritime college in New York that's like $18,000, but you can turn around and pay that off within a few years. I wish I'd done that instead of go into the military. ha ha!

[@ayoubtriaa1772]

it's always interesting with you, your presentation is fun to follow and it is so good, please keep up the good work. if i may suggest, make us a video about the "free ballast ship concept" , cheers

[@CasualNavigation]

Thanks ayoub. I am pleased you find them interesting and fun to follow

[@suSnayC]

@@CasualNavigation 🇵🇭🇵🇭🇵🇭🇵🇭🇵🇭❤🇵🇭🇵🇭🇵🇭🇵🇭🇵🇭😉🇵🇭

[@SondreIO]

Aaaand I'm never using the imperial system ever again. What the hell.

[@ninjaswordtothehead]

I already knew everything in this video but was still entertained. The skill and creativity of independent creators never fails to amaze.

[@quantomic1106]

You should make videos more often. They are very informative.

[@cpt.pejelagarto6932]

I’ve always sucked hard at math and just assumed that ships floated because of the air inside the hull... This clip was awesome! Even I understood it right away.

[@lyuboslavslavkov8881]

Well, you were kind of right. Ships do float because of the air in the hull bellow the waterline

[@TheOtherNeutrino]

It kinda does. The air being in the hull instead of something denser like water makes it float. The ships are heavy but the water they displace is heavier. It really is a testament to how heavy water really is.

[@Layarion]

i'd say you're right. because if you replace that air with cargo, sink the ship does

[@Exist64]

I can't believe nobody here is upset over him describing 1kg as a force and not a weight. Multiply that weight by 9,81m/s^2 to make it a force.

[@ericblaire6732]

Multiply that mass* by 9.81 to make it a weight*

[@hareecionelson5875]

A weight is a force. You mean mass

[@temporarychannelname8620]

1 kg can be a force or a mass. 1 kg mass = 1 kg force. Its just a convenient force to use in simple explanation like this, on Earth

[@VercilJuan]

1 kgf (kilogram of force) is 9.81 N, a derivative metric unit. its much more convenient working on forces on Earth's gravity, rather than multiplying everything to 9.8

[@JeromeProductions]

Weight is force though. It’s the force that keeps you (pull you to) on the surface of Earth.

[@iceslayer777]

Such a solid but underrated video. Surprised it doesn’t have more views but I learned a lot more than expected here!

[@guillaumeromain6694]

Your work really stands out. Content is great, delivery is pleasing and relaxing. Excellent work! Thank you 😊👍

[@ericblaire6732]

"Upwards force of 1 kilo:" Physicists: REEEEEEEEEEEEEEEEE

[@thesist8739]

That's what i am thinking after completing honers in physics i came to know this

[@aesir4134]

What?

[@restrictedaria7314]

Newton

[@neoxenoz3262]

The coin is heavier than a ship, because it sinks, a classic joke

[@shishupalsinghbhadouria7718]

Not heavier but it is more dense!

[@matt309]

@@shishupalsinghbhadouria7718 just like ur mum

[@latviantrainy968]

@@matt309 oooooooohhhhhhhhhhh......

[@zer0751]

@@matt309 ffs 😂

[@blairmarshall544]

A joke? More like a crap fact

[@ralphmontanez9716]

Such an informative clip mate.. you have explained a 1 semester class into 4min video clip 😂

[@8oh8Jungle]

I was genuinely wondering how metal floats but now it makes sense thanks

[@preetiprasad3933]

1:43, it’s mass not weight.

[@stephenshoihet2590]

@@Oussama-sabouh they can call it whatever they want, but kg are mass... weight is in newtons and kg force is not a proper unit. This is probably due to the incorrect way that someone decided to label metric scales in kg and the improper conversion that everyone does of kglb. This is a case where the imperial system is correct, as pounds are a unit of force and slugs are the imperial unit for mass.

[@glypnir]

Well, I've now binge watched through every video on the channel. Pretty good, although this one was the one that pretty much taught me nothing. But I think you've overall done a good job of keeping things simple enough for wide comprehension, but also interesting and informative for boat nerds with engineering degrees like me.

[@patakotisrinivas1918]

Really amazing...superb explaination...thanks a lot for throwing enough light of knowledge on us....

[@deaneprox]

Watched the vid, concluded it's magic. Science solved.

[@adrln1818]

Can u please do more videos on calculation on ships trim and stability and basic math on navigation. Thanks 😊

[@Ayo_itsme_Alanaaa]

Thank you for this. Me and my friends were arguing on how a ship floats…. 😂 We were all kind of right in a way.

[@MottyGlix]

Kilograms are units of mass, not weight. Weight is a *force* that is measured in newtons. Here on Earth, one kilogram weighs 9.81 newtons.

[@MichaelHales]

Thanks for showing us i liked and subscribed

[@chris_sndw]

TL;DW Ship is lighter than the water it displaces -> it floats

[@memerightsactivist7972]

Needed this so my From the Depths builds won’t absolutely suck in combat

[@poughkeepsieblue]

If it weighs as much as a duck, it floats And therefore, it's a witch!

[@3hutp]

So in short: whether it floats or not depends on whether it's lighter or heavier than water.

[@KonradTheWizzard]

Essentially yes. Slight correction though: more or less dense than water. How heavy it is does not matter, it is the relation between weight and volume. Something can be as heavy as a ton and float if it has a volume greater than 1m³, it can be light as 1 gram and sink if it displaces less than 1cm³. It has to be less dense than 1kg per liter (or 1 ton per cubic meter). Neat - right?

[@jordanforbes2557]

I know the difference in density between freshwater and saltwater is minimal but just wondering since cruise liners tend to be designed for saltwater, would they float on freshwater. That might sound like a ridiculous question, but in engineering the calculations are extremely precise, or perhaps the bottom of the hull might sink a bit lower in relation to the water line. Anyone know? Edit: nevermind I finished watching the video and my question was answered. Brilliant video.

[@fukkitful]

Ballast tanks...

[@Raptorfilmz]

Awesome, thanks! Would have been perfect if you'd described forces in newtons rather than kg though :)

[@EdinBasic12]

I have a little ship on one lake in Bosnia and I must say its fun to be able to get there an cool yourself off on summer. We are planning on getting internet smart tv and bunch of other things In it! I started to love ships, those things that float in the water by some laws (This was poetical)

[@ashby7m]

Answered every question I had!

[@LearnwithAGC8755]

Crystal Clear brother ❤

I went from ‘Is it possible to make a magnetic shield’ to ‘Could people theoretically walk on water’

[@camronpotter8547]

Lmao i am on the boat in the thumbnail right now😂

[@jamnchips]

I know it's 11 months late but did you have a good time?

[@hamzab3659]

@@jamnchips i know it’s 6 monts late but do you think he will ever reply ?

[@psykey]

@@hamzab3659 i know its 6 days late, but why did you ask?

[@mohgt6955]

@@psykey i know its 1 month late but stfu

[@fukkitful]

@@hamzab3659 Still waiting on that reply I see....

[@LKDesign]

So if the brick would fall onto a scale on the bottom of the tank, the scale would show the mass of the brick minus 1 kg?

[@pikolovesolivia3693]

Your channel is always interesting because I love boats, and always dreamt of sailing the world in a luxurious cruiser. 🛳🌅🏖🏝🌴💎🍸🌊 Thanks for sharing this vid. 😊 I wonder... is it possible for a catamaran to become as big as a cruiser like the Symphony of the Seas? 😯 Or should it only be one hull for the largest of ships? 😅 Just curious, if one anywhere near as large as that cruiser is ever built. 🛳 Anyway, I'm just asking because I love catamarans the most for these boats look the most beautiful to me. ⛵

[@CasualNavigation]

Thanks Piko. Glad you enjoy the content. I see no reason why a cat can't get that big. Strictly speaking, just adding a platform between two hulls that size would make a cat. Controlling and manoeuvring it may be tricky though

[@pikolovesolivia3693]

Much appreciated for the reply. 🛳⛵

[@suSnayC]

@@CasualNavigation okay!🇵🇭😉

[@smurface549]

Check out the "Pioneering Spirit". She's a cat made of two hulls the size of a VLCC.

[@vhhawk]

And today I finally understand how the Plimsouls got their band name.

[@5313030]

Brilliant explanation.

[@IamKudos]

Weight isnt quite the product of density and volume

[@mrs2832]

Thank you. Superb explanation.

[@amunyelamarius3405]

Thanks alot, I now have a clue on why ships floats

[@barryvideos4472]

Thank you for clearing this up????

[@lordcommander5015]

At 3:09 you used "tons" instead of the metric "tonnes." While roughly equal a metric ton is 1.1 times an short ton, or 1.01 times an imperial ton.

[@theoneandonlyhooda]

isn't it supposed to be in kg

[@cyclops9750]

Learning about Ships is very interesting

[@thesist8739]

Mass= volume * density Weight is a force its unit is Newton not kilogram(kg) Weight = mass * g(acceleration due to gravity)

[@nagyandras8857]

kgf, is kilogramm force, the force 1 kilogram has. kinda oddball unit but still is in use.

[@DaveSCameron]

Ohms Law is a key equation here, never lose sight of the fact that Scouser are #MilesAhead

[@damianjob53]

1kg is mass not weight

[@gerardanthony1450]

best explanation out there

[@Samiharoun]

that was the easiest to understand video about buoyancy i have sean. get it, i said sea. instead of see.

[@lks5878]

Everybody be talkin about comic sans but nobody noticed how this video is 4:20 long?

[@antonman1234]

NO ONE CARES

[@lks5878]

@@antonman1234 bruh no one asked for your opinion

[@grondhero]

@@lks5878 Yet, you _did_ ask for his opinion by asking a question to everyone. ;)

[@lks5878]

@@grondhero well I asked if anyone noticed it, not if they cared

[@alexandermadu3801]

I finally understand it, thank you so much, tho to make it easier for a lot of people, in the example of the ship, when it displaces 180,000m3 of water, you jumped into talking about the weight of water displaced being 180,000 tons, you didn’t explain that by tons you mean 180,000,000kg of water Which you got by multiplying 180,000m3 by 1000kg/m3. I feel like it’s gonna help a lot of people grasp what your explanation. Thank you so much.

[@vimalramachandran]

Well explained!

[@RichJord0331]

Mechanical engineer here, the nerd in me just really wants to know the math behind the width/depth of the haul relative to the amount of water it displaces. There has to be a specific number they stay between that’s sort of the “golden” number for floatation.

[@debonair6183]

Great explanation except that Kilo is a unit of mass. You still need to multiply it with acceleration due gravity in order to be represented as weight/force.

[@jackvac1918]

It's weight is still the same in kilos as the layman uses it (technically it's the kilogram-force). Multiplying kilos by gravitational acceleration only converts it into newtons (a unit definitely not used by the layman).

[@jamesmorrissette741]

TL; DW the more area that the boats hull has, the easier it will float

[@howardjohnson2138]

Thank you.

[@bablisoni6401]

Nice

[@CARRJ142]

Another great video.

[@TSotP]

Without watching any more of the video (12s in). You have to work out what the average density of the volume below the surface is. And if it is less than that of the water, it will float. Imagine a lead balloon. The skin might be lead and way more dense than water, but most of it's volume is air, which is way less than water. When you take the mass of Air and add the mass of lead then divide by volume, you get the average density. Which is probably less than water, so the whole thing floats. Boats are the same. As long as the average density doesn't change (by more dense water pouring in and replacing less dense air) it'll keep floating. This was less of an issue in the past because most boats/ships were made of wood, which in general is already less dense than water.

[@ahmedfaseeh9158]

More deep but simple explanation please.

[@erikgood732]

Because they’re painted with water repellent paint,that’s why they don’t paint the anchor.

[@Nileshmadhav95]

Yes, you are right, water repellent paint let a ship float, this video is telling us lies.

[@Kay-dt5gn]

I tried that home , my item still sunk ! I just don’t get! Too brilliant and complicated 😊 I will keep on trying… lol 😊

[@kailasnath6930]

Excellent

[@bandanakumari5186]

Thank you so much

[@srr1887]

Those royal caribbean ships is like millions TONS or something and it still floats ! Damn , engineering is just mind boggling if u are thinking how every stuff "happened" and "possible"

[@whoathatsalotofdamage3718]

What i got from this is bascially: Big ships float because long is a good way to increase displacement for ships

[@josephnyakundi7593]

Great principles in physics.

[@abysswalker2403]

the brick confuses me, 20x5x10 would be 1000 yes? which means 1000 cm^3, but he comes out with 0.001m,^3 which is just 1 cm^3, but the math is correct because decimals make it smaller, so you just arent supposed to make it meters in that instance?

[@nishantintouch]

Good explanation. Tx

[@adilnawaz6559]

Kilo is the mass not weight.... For weight you have to convert it into newtons.

[@PennyGraham]

thx now my lego boat will float

[@PennyGraham]

@james braselton ?????

[@OhFishyFish]

The number of people here who haven't learned this in school is terrifying, and they can vote.

[@XPLAlN]

the greatest argument against democracy used to be 5 minutes talking to a man in the street. It is now 2 minutes reading the comments on YT.

[@petefluffy7420]

Because, if it did not float it would not be called a ship, rather, it would be called an artificial reef.

[@ingvarhallstrom2306]

What is counter intuitive is the thought that small boats would be "better" at floating than large ships.

[@anormalcommentor9452]

the opposite as expected

[@DajesOfficial]

The smaller an object the easier to get it to float due to easier construction (small boats don't require advanced materials to stay intact under its own weight and water pressure) and surface tension (you could try dropping some powder on water and see that even without tricky design most powder particles float easily).

[@JohnJohn-mk7nc]

So did noah use this principal with the ark…..? Or did he just guess it?

[@mikey10006]

What about the increasing buoyancy at various depths

[@cpotisch]

Shemsy Boats don’t sit low enough for that to really matter.

[@saimanish7879]

Bro...Its not the Weight but it is Mass=Density*Volume...Weight's unit is Newton and Mass unit is Kilogram...please correct it if u can...I got confused for sometime though i well know this units before.

[@Nadia..J]

Great voice!

[@epiendless1128]

Even though I know mass isn't a force, and would often be pedantic enought to point it out, I managed to watch and understand the whole video without noticing the mistake/simplification. :-) Side note, while mass isn't a force, you CAN have pounds of force, since pounds of force (lbf) and pounds of mass (lbm) are both formally declared units. In modern definition 1lbf = 4.45Newton, regardless of local gravity, so 1 pound of mass weighs approx 1 pound of force on Earth and 1/6 pound of force on the Moon. I looked this up after witnessing a blazing row between two clever people who should have known better. They both knew their physics, but both said "pounds" when one meant lbf and one meant lbm. If we'd avoided the metric system, the video would have been correct. But there would likely still have been an argument. :-)

[@Tyneo4231]

Nice

[@JeffreyEpsteinJr.]

Does this same principle apply on other planets with different levels of gravity?

[@antonvisbystergaard8413]

Yes. Gravity will effect the fluid and the floating object the same.

[@DlcEnergy]

On my small planet, the ocean has learned to float with us. It was a cold dark night of sailing beneath the fish bubbles... But little did we all know those weren't just any fish... Those were pirate fish. They were comin from the bubbles! There was nowhere to run. We had to play them at their own game. It was all out fish warfare. We had the battle of our lives that night... But unfortunately not all of us could make it. Sometimes when i'm sailing, i look up and think... They're riding those bubbles up there now... And maybe some day we'll meet again.

[@zachbaker723]

Come to Brazil!!!!!

[@maecarpenter69]

Here I am, loving the content, but yelling at my screen... 'Newtons' 'Mass not Weight' Other than that, great, thank you

[@TheMetropolisKid1]

thank you! Now I can win an argument!!

[@mitesh2k3]

Did u win?

[@Mahmil]

but the thoughtful question is if we put a cylinder inside a bigger cylinder and change the volume of the inner cylinder which effectively does not change the volume of the outer cylinder. would it affect the buoyancy of the outer cylinder?

[@Malorn0]

...No, it would not. It might change the weight, but the buoyancy itself would be unaffected.

[@spyrmac]

New topic: new bow designs? I mean make a video about that.

[@davidmg1925]

2:01 misleading: abrick weighing 1kg would float? no other wise excellent

[@ToddyBeer69]

Do Vessels cause sea level rise?

[@GalenMarekOfficial]

Yes, but one vessel only makes it rise by like 0,000000000000000000000000000001% or something...so technically yes but not really measureable. Its like the fact that touching a table makes it hotter since your touch transfers energy...but you can never feel it because its also just a tiny percentage.

[@ToddyBeer69]

@@GalenMarekOfficial so there is a rise 👋🏼😎 Thanx

[@framurofficial]

Why do boats and ships float? Because there is air inside so that they cant sink or in short they are hollow

[@shayaandanish5831]

wieght is measured in Kilos?

[@hallo0hoi]

Yes, that is the International System of Units...

[@anhondacivic6541]

Weight is measured in newtons because it's a force, mass is measured in kilos

[@CaesarCassius]

What?

[@shawnm.1540]

Same way small ships float.

[@booksandstuff3983]

I tried so hard to keep up with this but its SO CONFUSING 😭 Fifth grade is hard :(

[@tyler1450]

It’s hard,but necessary sadly

[@Amr51002]

Awesome

[@Toma-621]

now i know why timothy’s mother doesn’t wear a life jacket

[@JimMonsanto]

Could you explain why longer ships move faster than shorter ships?

[@jazznjayy]

how does a ship displace water when its docked

[@charliebrett7510]

What do you mean by displaces. Does that just mean the water rises like you showed in the video? I’m sorry I still don’t get it. Surely the volume of the object=volume of water that moves up/is displaced. why does the volume of the object submerged = the WEIGHT of the water displaced and not the volume of water displaced?? Thanks so much

[@Malorn0]

An object will submerge until it has displaced exactly the volume of water equal to it's weight. It's tidy that way.

[@Velktron]

Well, I knew of people who still don't understand/believe how airplanes fly, even though the basic airfoil principle is (,or at least was) explained in elementary school texts. But needing to explain buoyancy.... it's literally ancient history. Eureka and all.

[@tapiwachitemerere5730]

So the shape of the object has nothing to do with floating?

[@CasualNavigation]

Correct. It is only down to the amount of fluid displaced.