Archimedes principle and buoyant force | Fluids | Physics | Khan Academy

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  • Опубліковано 18 кві 2008
  • Introduction to Archimedes' principle and buoyant force. Created by Sal Khan.
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    Physics on Khan Academy: Physics is the study of the basic principles that govern the physical world around us. We'll start by looking at motion itself. Then, we'll learn about forces, momentum, energy, and other concepts in lots of different physical situations. To get the most out of physics, you'll need a solid understanding of algebra and a basic understanding of trigonometry.
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КОМЕНТАРІ • 119

  • @arnoldchristian9501
    @arnoldchristian9501 6 років тому +121

    Bro how do you know every single thing in the world? lmao

  • @ModernWoodShop
    @ModernWoodShop 6 років тому +75

    "If you can't explain it simply, you don't understand it well enough." -Albert Einstein

    • @the_unconscious_mindthe_le3344
      @the_unconscious_mindthe_le3344 6 років тому +2

      Maxwell Gunter 😂😂😂😆😃

    • @Ndfull
      @Ndfull Рік тому

      @@the_unconscious_mindthe_le3344 1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqquq

    • @Ndfull
      @Ndfull Рік тому

      @@the_unconscious_mindthe_le3344 0000000

  • @laputahayom
    @laputahayom 15 років тому +19

    wow you just made so MUCH SENSE
    you have a gift for teaching.
    that never made sense to me before.
    thank you so much

  • @artakisthebest
    @artakisthebest 12 років тому +24

    hehe, I actually only made it halfway through his trigonometry playlist the day before my trig exam havving never looked at my other teachers notes, and got 84 percent in my trig exam! And that was a college level test :D

  • @joeymama648
    @joeymama648 10 років тому +11

    his voice is SOOOOO relaxing

  • @sehmio
    @sehmio 7 років тому +13

    This was fantastic! Background in why its F=pvg!

  • @MandaNovokmet
    @MandaNovokmet 6 років тому +1

    This is a beautiful video!! Really made the concept clear, thank you! God bless

  • @kanaeroseweld2237
    @kanaeroseweld2237 Рік тому +1

    Thanks bro. I have been trying to undertsand this principle for hours. You saved me days of trying to think. Thanks

  • @anber4129
    @anber4129 5 років тому

    Beautifully done. Very easy to follow. Very flowing.

  • @Chelsea-gs7qj
    @Chelsea-gs7qj 7 років тому +53

    I usually love these videos but I'm literally lost

    • @keamorshedsoccer1382
      @keamorshedsoccer1382 7 років тому +3

      Chelsea Osuji Khan made this video wayyyyyy to mathematic🙏🏽😬

  • @TACZero1
    @TACZero1 12 років тому +2

    My teacher for some reason made us learn fluids by ourselves, which i think is the hardest thing we've done so far. so thank you for your videos because i have been so lost

  • @ArchmageMokokong
    @ArchmageMokokong 6 років тому

    his voice is sooo relaxing and his video is so wonderful teacher to me.

  • @NilanjanaLodh
    @NilanjanaLodh 13 років тому +1

    really wonderful!!no other video on the net is as good as urs!u jus rock

  • @htavli
    @htavli 2 роки тому +1

    This video was very helpful. Thank you!

  • @nenoo1536
    @nenoo1536 Рік тому +2

    this is actually really helpful!! bless you :)

  • @abdosamr4639
    @abdosamr4639 2 роки тому +1

    Pressure acts in perpendicular directions, not in all directions.

  • @ParadiXe311
    @ParadiXe311 3 роки тому +2

    This video was so educational, I just jumped out of the bathtub, running down the street naked, yelling "Eureka!"

  • @niconikko
    @niconikko 12 років тому +3

    Mr. Sal, you're not just a great teacher, but you're also a great magician. You helped us in showing the formula for buoyant force like magic. THANKS!!!

  • @artakisthebest
    @artakisthebest 12 років тому

    Wow that was a very intuitive example my friend! Did you read that somewhere or you thought of it, I think thats beautiful, really complements the mathematical proof of archimedes principle well.

  • @josemolina5423
    @josemolina5423 6 років тому +7

    Water molecule as a sphere?
    J. Dalton likes this

  • @sureshchandrapal2320
    @sureshchandrapal2320 2 роки тому +1

    Thank u so much....I was extremely confused in it but now it is crystal clear ....thank u million times
    Hare krishna

  • @sergiomuniz350
    @sergiomuniz350 6 років тому

    great video. in the book they have f= gamma times the volume in which you have d cubed times rho times gravity and rho times gravity makes gamma so that explains a lot.

  • @dst7ssa
    @dst7ssa 14 років тому +4

    Funny I have a fluids exam tomorrow and am gaining confidence as I watch your videos. I cant believe I didn't see this before my first exams. Now I feel like I understand enough to actually teach someone. Captain Sal explain things so simply like you do . thanks

    • @Smokie_bear9896
      @Smokie_bear9896 6 років тому +1

      woah you’re from the past

    • @ottavari746
      @ottavari746 6 років тому

      Smokie Bear lol

    • @Aaliyah_Matyevna
      @Aaliyah_Matyevna 2 роки тому +1

      Were you in college at that time?You have grown up so much now then.

    • @amirabbas0
      @amirabbas0 Рік тому

      @@Smokie_bear9896 now you're from the past

    • @Smokie_bear9896
      @Smokie_bear9896 Рік тому

      @@amirabbas0 now i'm from the present

  • @flimsyfox
    @flimsyfox 4 роки тому

    I just had a "mind-blown" moment.

  • @SwayamKrishnaartsandcrafts
    @SwayamKrishnaartsandcrafts 6 місяців тому

    It has been 15 yrs but still this video helps

  • @bubbybumble616
    @bubbybumble616 3 роки тому +1

    bro how does this video from 2008 perfectly explain one of the harder concepts for me to grasp. how did I not understand this before?

  • @unitelanka
    @unitelanka 8 років тому +10

    the explanation that finally ties it all to weight is really really neat.

  • @artakisthebest
    @artakisthebest 12 років тому +7

    respect man, figuring things out for yourself will really make sure it sticks in your brain! I aspire to be an engineer, and I could never just 'trust' in all the formulas I use, Id like to prove them myself. I hope I can say the same when im in the last year of my degree where things are bound to be not as intuitive. At the moment im having trouble grapsing the concept of Enthalpy. Do you think you could explain enthalpy for me :P

    • @soumyashreebiswal14
      @soumyashreebiswal14 Рік тому +1

      Absolutely agree with you, man! Same aim here, and I too always try to prove stuff myself. Not a bad habit to have, is it? (Jeez when you commented this, I was like 8 years old haha)

  • @slmUSA
    @slmUSA 13 років тому +1

    Thank you!

  • @psbbiaku640
    @psbbiaku640 7 років тому +1

    hey sal I am ur no.1 fan

  • @megaelliott
    @megaelliott 15 років тому +2

    Look up rho(greek alphabet) on google and you will see that the capital version looks slightly different. I advise that you use that as rho in your own work as it is less confusing

  • @hemantvaish5658
    @hemantvaish5658 6 років тому

    good vidd
    sir plz aaap practically videos banayq karo
    jaise aaap specific gravity ki bnayai hh
    vry nyc vidd
    plzz

  • @firaolmulugeta9928
    @firaolmulugeta9928 3 роки тому +1

    wow very nice i uderstand every thing what he says

  • @MellowCruisin
    @MellowCruisin 13 років тому +1

    I have a question for you. If an object is at the very bottom of a jar of water with no room for water between the object and bottom of jar, how does the object still buoy up if there isn't water below it?

  • @MitchelChabu-yl2xp
    @MitchelChabu-yl2xp 10 місяців тому

    You make me want to say I love physics

  • @specialparadise
    @specialparadise 6 років тому +7

    Anyone else had a Eureka moment?

  • @willpaisley7828
    @willpaisley7828 6 років тому +3

    Does this assume the mass of the cube is negligible

  • @Perrihan
    @Perrihan 4 роки тому

    Thank you so much!

  • @stephenkong3155
    @stephenkong3155 7 років тому +1

    May I ask why does the net force equals to the buoyant force? Like what's the reason they equal?

  • @BettyNalugo-et9sp
    @BettyNalugo-et9sp 9 місяців тому

    so wonderful 💖

  • @CcanCcaglar
    @CcanCcaglar 13 років тому +3

    omg khan when im rich im guna give you so much money

  • @vinayseth1114
    @vinayseth1114 8 років тому +3

    But shouldn't the net force be 0, otherwise the cube would keep jutting upwards and then get pushed out of the water?

    • @amrshehab7019
      @amrshehab7019 5 років тому +2

      It is another thing he is just calculating the net force due to the pressure difference which is called buyonce force but there is also another force which is the gravity so when we apply neowton’s second law on this body we will say that the net force = mg (gravity[downwards]) - B (buyonce force[upwards])
      And if they are equal it will be submerged in the fluid if the gravity is greater it will sink if buyonce force is greater it will float untill some of it get out of the fluid that the dicplaced fluid is less so the buyonce force is less to be in equilibrium with the force of gravity

  • @reesejpuc
    @reesejpuc 14 років тому +1

    sal, 100 years from now, you will have your own unit of measurement named after you. The sal or the kahn.

  • @kanikachaudhary6089
    @kanikachaudhary6089 3 роки тому +1

    ONE QUESTION HOW PRESSURE ACTING IN ALL DIRECTION IT SHOULD ACT DOWNWARD ONLY HOW LEFT AND RIGHT

  • @nolwazihlophe580
    @nolwazihlophe580 5 років тому +1

    thank you

  • @SAISRIKAR2002
    @SAISRIKAR2002 5 років тому +3

    What happened to the wEight of the cube while calculating the net force?

    • @Jay-jk7jv
      @Jay-jk7jv 2 роки тому

      The net force calculated here is the force acting on the cube due to pressure. The weight of the cube is acting downwards while the net force due to pressure is acting upwards. That means the net force due to pressure will work against the weight of the cube. This is what makes the cube feel lighter when it’s in the liquid.
      I'm 2 years late, but I just learned this concept from this video and thought I should answer. You know, just to see if I can explain it:)

  • @ANUPAMAMATHEWPHD
    @ANUPAMAMATHEWPHD 5 років тому

    Is the box in static equilibrium or is it moving up??

  • @himanshusharma9981
    @himanshusharma9981 5 років тому

    nice derivation, but what if we take the example of a human being and try to derive Archimedes principle .how will u take out the volume of a human.

  • @rotflmaopmpqxyz
    @rotflmaopmpqxyz 13 років тому +1

    So P stands for pressure, and p is also units for momentum AND density? these confuse me. Also Mass and meters confuse me too

  • @maxtan4471
    @maxtan4471 3 роки тому

    Why the force act on the top and bottom of the cube are not the same, since it is in static form?

  • @spatel6230
    @spatel6230 3 роки тому +1

    when Sal cancelled out those two phg's, I may have been more aroused than I've ever been in my life

  • @mousaalsaeed9410
    @mousaalsaeed9410 7 років тому +1

    what happened for weight of object ??

  • @KavangWase
    @KavangWase 5 місяців тому

    I'm confuse. Fnet=(d•p•g)d^2 if you are going to expand that, why does both density (p) and gravitational acceleration (g) are not multipled by d^2 and only d is multipled by d^2 giving d^3?

  • @dravinashiyer936
    @dravinashiyer936 5 років тому

    With the hydrostatic eqn derive bouyant force of submerged body.. Put answer of this question please

  • @fufuisgood
    @fufuisgood 6 років тому

    I did not quite understand "volume of the water displaced" I'm from Denmark and your videos are very helpful, but there's one thing that I did not quite catch..

    • @Arafat-my6fe
      @Arafat-my6fe 4 роки тому +1

      when u stick an object into the water, and exactly where u stick it into the water, the water of that very place has to move out to make room for the object u r sticking or putting there. And the volume or amount of water was moved(displaced) is called the volume of the water displaced. Hope, that helps. 😀

    • @fufuisgood
      @fufuisgood 4 роки тому +1

      @@Arafat-my6fe thankyou!! I totally forgot about it since it was 2 years ago ahahah

  • @DbzFighter02
    @DbzFighter02 12 років тому +1

    2 years later, I'm in the exact same position. LOLLLL!

  • @eslamnoaman3802
    @eslamnoaman3802 5 років тому +4

    why we don't say that pressure at the top is equal to (roh+g+h+p atm)?

    • @ahsansafeer5246
      @ahsansafeer5246 3 роки тому

      It's a vacuum I guess

    • @benricosimamora3429
      @benricosimamora3429 3 роки тому

      (in case someone is still confuse about this). the pressure that was mentioned must be gage pressure (not absolute pressure) which is relative to atmospheric pressure, so we dont need to add p atm.

    • @predatorgaming895
      @predatorgaming895 3 роки тому

      @@ahsansafeer5246 no gauge

  • @Ichneumonidae2
    @Ichneumonidae2 12 років тому

    great video, thanks!

  • @anotherdoseyt
    @anotherdoseyt 7 років тому

    So straight to a cup of water... no good morning 😂

  • @fablihakhan9265
    @fablihakhan9265 6 років тому +2

    Why am i not taking the height from the very bottom of the cup to determine the pressure at the bottom of the cube?

    • @fablihakhan9265
      @fablihakhan9265 6 років тому

      Since the water from below the cube is also exerting some pressure on the cube

    • @36sufchan
      @36sufchan 6 років тому

      If you consider height from the bottom; then it would make pressure higher at more distant points from the Earth (slightly less acceleration due to gravity); but since it doesn't work for columns infinitely long, it is not acceptable.

  • @amrshehab7019
    @amrshehab7019 5 років тому

    But this prove is for regular body how could we apply archemedis principle for spheres and irregular bodies ?

  • @SkyOnUrSide
    @SkyOnUrSide Рік тому +2

    ITS FREAKING 2022 it was 2008 dayum

  • @drdkvetbiotech
    @drdkvetbiotech 7 років тому +4

    why didn't we multiply d^2 with g and rho?

    • @rjk368
      @rjk368 6 років тому +3

      I believe it was (dpg)*d^2. However, (dpg) means (d*p*g), not (d+p+g). So, it is (d*p*g)*d^2. Now, multiplication is commutative (can be done in any order) and associative (grouping doesn't matter if all operations are multiplication). Since all of the operations are multiplication, it is: d* p * g * d^2 = d * d^2 * p * g = d^3 * p * g. The reason you don't distribute is because you only distribute the coefficient when the operation inside the parentheses is addition (for example, 2(4+6) = 2 * 4 + 2 * 6 = 8 + 12 = 20).

    • @91755103
      @91755103 6 років тому

      It's just to show that the buoyant force is the product of the volume displaced by the submerged object, and the liquid's specific weight.

  • @illiums410
    @illiums410 7 років тому +6

    Hotel?

  • @adas2922
    @adas2922 10 років тому

    thanks

  • @23Foxford
    @23Foxford 10 років тому +4

    Love his videos, but his idea of fun with friends can result in pretty awkward situation

    • @brightface5005
      @brightface5005 8 років тому +2

      i wonder if you would reply to this

    • @yiumyoumsan6997
      @yiumyoumsan6997 4 роки тому

      @@brightface5005 I wonder if you would reply to this.

  • @arfaouiarij8938
    @arfaouiarij8938 6 років тому

    I'm confused why you never spoke about the force of gravity ?

  • @usersersandrenfcgami
    @usersersandrenfcgami 4 роки тому

    why did he ignored the weight of the cube when calculating the net force ?

  • @Henryy97
    @Henryy97 9 років тому +5

    i love you.

  • @taymrafid9139
    @taymrafid9139 3 роки тому +1

    My guy made the video before I was born lmao

  • @gretawilliams8799
    @gretawilliams8799 6 років тому

    That's through physics perspective but...
    The answer of why upthrust is created, is purely philosophical...
    Does pure water produce upthrust?? I think, upthrust effect is due to the repulsion between same charged ions....
    How do you put it(philosophy) into science ...
    The tendency of any body to remain undisturbed or in their natural state, upthrust is due to them resisting disturbance,.
    That's basically all upward directed forces: Normal contact force, Upthrust, ....

  • @sheme110
    @sheme110 4 роки тому

    Isn't pB also acting downward not upward?

  • @arulselvan4067
    @arulselvan4067 4 роки тому

    Buoyant force is the same as upthrust right? Sorry my English isn't that good

  • @LNasterio
    @LNasterio 12 років тому

    Imagine a cup of water as a box of solid balls.
    when you sink into middle of that box of solid balls.
    the balls on top will apply a force acting you downwards right?
    and the balls at the bottom of you will apply a "reaction force" acting on you upwards, And this reaction force is equal to weight of the object within the water plus the "balls"
    on top
    hope it make sense?

  • @midnightsilverpuppy
    @midnightsilverpuppy 7 років тому

    That's interesting

  • @Makedonche
    @Makedonche 13 років тому

    @reesejpuc I'd go for the sal.

  • @erikm9768
    @erikm9768 8 років тому +24

    Jesus what a mess. Also, i was hoping to understand how pressure actually affects archimedes

  • @eniamrahc73
    @eniamrahc73 6 років тому

    I love you so much.

  • @rachellepangilinan5201
    @rachellepangilinan5201 Рік тому +1

    We have a kid typing

  • @yashilakra5474
    @yashilakra5474 6 років тому

    The

  • @yashilakra5474
    @yashilakra5474 6 років тому

    The voice is very slow

  • @sheu_her
    @sheu_her 6 років тому

    Thats is not a P, please

  • @kenneffy1
    @kenneffy1 13 років тому

    woah. lol

  • @samiyahshua
    @samiyahshua 6 років тому

    #flatearthproof

  • @jaggitsingh9892
    @jaggitsingh9892 3 роки тому

    i just dont understand....i am in 6th grade and my mother makes me learn these things....... lol

  • @samiyahshua
    @samiyahshua 6 років тому

    #flatearhclues #flatearthproof

  • @Somali_omega
    @Somali_omega 10 років тому

    not what i was looking for mate. Salman can do better