Finding height of fluid in a barometer | Fluids | Physics | Khan Academy

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  • Опубликовано: 15 окт 2024
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    Using our understanding of fluid pressure to figure out the height of a column of mercury. Created by Sal Khan.
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Комментарии • 76

  • @piacorujo4161
    @piacorujo4161 4 года назад +14

    this dude is the reason i'm going to do well on the mcat

  • @aksh_x_
    @aksh_x_ 3 года назад +3

    It's hard to believe that I'm getting all this for free! Thanks a lot Sal, and I will sure donate once I start earning.

  • @IdoAloni123
    @IdoAloni123 8 лет назад +11

    N is not M*m^2/sec^2, it is J
    You just wrote N/m^3 instead N/m^2 (pressure)
    The mistake is in the last equation

  • @alig5904
    @alig5904 10 лет назад +24

    1 atm = 101.3 kpa ?

    • @Fin2001
      @Fin2001 5 лет назад +2

      Ali G 101325 Pa

  • @calebcar
    @calebcar 15 лет назад +2

    This series is wonderful. I'm taking an on line ap physics course and there is no audiovisual. You are a life saver.
    One thing I don't understand. I did not see that you made reference to the diameter of the test tube. If the test tube took up almost the entire diameter of the bowl the mercury was in, wouldn't you have a tiny surface area of air pushing a large surface of mercury up. Why does the height not depend on the relative surface area of air and mercury?

    • @coolradio123
      @coolradio123 2 года назад

      did you ever find out why? 🙂

    • @markharlock6474
      @markharlock6474 Год назад +1

      It is counter-intuitive, but the pressure exerted at the base of a column of liquid is independent of the diameter of the column (in this case a long vertical test tube containing mercury). This can be shown in the derivation of the formula P=pgh used in this video. With the density of mercury (p) and 'g' both constants, the pressure (P) at the base of the column of fluid is seen to be directly proportional only to the height (h) of the column of fluid. So the diameter of the tube does not affect the equilibrium level of the fluid column. However, you would have to be sensible about choosing larger diameter tube since this would require a larger volume of mercury in the 'bowl'.

  • @prabhanshukatiyar213
    @prabhanshukatiyar213 7 лет назад +23

    you having cold, sal?

  • @erictoepfer4655
    @erictoepfer4655 10 лет назад +12

    1 atm = 101325 Pa

  • @mrd7765
    @mrd7765 2 года назад

    It would be great if it was Mahesh sir...I can't understand Sal sir but I can understand anything easily when it was Mahesh sir..

  • @8299naresh
    @8299naresh 12 лет назад +2

    I have started loving Physics.......(nd I'm doing my computer science)

  • @GreerFried
    @GreerFried 5 лет назад +1

    8:16 it should be m^2.

  • @jonrty007
    @jonrty007 13 лет назад +5

    Isn't 1 atm = 101.325 kPa or 101,325 Pa? :O
    Other than that. You are probably one of, if not, the greatest Physics teachers alive.

  • @uriyacohen-eliya7932
    @uriyacohen-eliya7932 8 лет назад +4

    Amateur mistake on the units there sal.... N is kg*m/s^2, not kg*m^2/s^2, you wouldn't be left with m as it would cancel.... Your mistake was with canceling 1/m^2 in the numerator with 1/m^3 on the denominator......

  • @seekdragonflies
    @seekdragonflies 14 лет назад +3

    he is talking about mercury when he refers to 13.6 g/cm^3 or 13,600 kg/m^3 which is the density of mercury :)

  • @Joikakaker
    @Joikakaker 14 лет назад

    Why are you defining 1 atm as being at sealevel in Paris, France? It's not constant there, nor is it constant anywhere else. I guess you already know this, and I guess you just say it to simplify things, but it's quite important to know that pressure is dynamic (hence our dynamic weather)

  • @asganesantpr
    @asganesantpr 9 лет назад +1

    whether there would be some changes in mercury level(760 to anything) if i change the area of the bowl ??

  • @Peter_1986
    @Peter_1986 11 лет назад

    "Aluminium" is more consistent with other metallic elements, like sodium, magnesium calcium etc, and from a Latin perspective more correct.

  • @biochem86
    @biochem86 11 лет назад +3

    1 atm=101325 pascals or 101.325kpa

  • @nguyenphuonganh340
    @nguyenphuonganh340 3 года назад

    At the last minute, 103000 N/m^2 should be the numerator instead of 103000 N/m^3. And 1N = (1 kg * 1m)/(s^2).

  • @anilsharma-ev2my
    @anilsharma-ev2my 4 года назад

    Half filled barometer doings some work or not ?

  • @VSmassacre
    @VSmassacre 13 лет назад +5

    "Let me draw a bowl...a bowl.. And in this bowl i have Mercury"
    -LOL

  • @Joikakaker
    @Joikakaker 14 лет назад

    @jiggaluv123 I wouldn't say that saying that pressure is dynamic is very complicated, rather quite intuitive

  • @asherzephyr
    @asherzephyr 15 лет назад

    So does the mercury go into the tube because the atmospheric pressure basically pushes it into the tube?

  • @michellephil413
    @michellephil413 8 лет назад +3

    lmao i love the word vaccuum bc theres 2 u's in a row

  • @adas2922
    @adas2922 11 лет назад +1

    thanks

  • @arjunaumesh5375
    @arjunaumesh5375 4 года назад

    Kg m/s^2 is N
    And pressure is N/m^2
    Small error

  • @Vayrus53
    @Vayrus53 12 лет назад +1

    yes it is 101325 pascal. 1 atm = 1.01325x10^5 Pa

  • @thienfoil
    @thienfoil 13 лет назад

    @g37muflih force has to do with mass and accel/gravity. Pressure is force over an area. Force doesnt need to stay constant, but pressure in liquid does.

  • @2007excalibur2007
    @2007excalibur2007 13 лет назад

    @g37muflih The same reason why we can't call pressure as force.

  • @joltzvoltz6314
    @joltzvoltz6314 7 лет назад +8

    isn't 1atm= 101300 pa

  • @nestoloco
    @nestoloco 11 лет назад +2

    I noticed the same thing, 1atm=101325 Pa

  • @travel_n_fun
    @travel_n_fun 14 лет назад

    Ehm, in the formula (bottom right hand corner, you wrote 103,000N/m^3, when it should be m^2 :)...
    Thanks a lot Sal!!!!

  • @TurbotortoiseStickle
    @TurbotortoiseStickle 13 лет назад

    Thank you, I'm actually having fun with this.

  • @joel7308
    @joel7308 13 лет назад

    u r great, thank u, other parts r also good

  • @lastword5714
    @lastword5714 8 лет назад

    can u please provide lecture on gear design?

  • @guitarded0081
    @guitarded0081 11 лет назад

    does that mean that no matter how big the test tube the mercury will always goe up 0.77 m at 1 atm ???

  • @xdodanielodx3835
    @xdodanielodx3835 7 лет назад +1

    This vid triggered my imagination. Smh. It was useful, though. As always. Keep it up!

  • @7starblast414
    @7starblast414 6 лет назад +1

    wait,if an elephant smacks u, u get hurt due to the pressure or its momentum?

    • @kkngenomesho7744
      @kkngenomesho7744 6 лет назад

      come on...

    • @chrisbotos
      @chrisbotos 4 года назад

      You hurt because your nerves feel the change in the pressure and inform the brain with pain signals. But you also hurt because the momentum resulted in a force on your nerves that broke parts of them, in this case your nerves also send signals of pain. So the answer is both.

    • @7starblast414
      @7starblast414 4 года назад

      @@chrisbotos well thanks for reminding me i commented something that stupid over two years ago. Thanks for answering anyway haha

  • @d3fil4dddsspecz
    @d3fil4dddsspecz 3 года назад

    1 atmosphere is 101k pascal not 103k

  • @dinmorerengeit
    @dinmorerengeit 13 лет назад

    is it just me or does the units not work out..?
    isnt N= m*a = kg*m/s^2?
    N =/= kg*m^2/s
    wich means he will not end up with .77m in his answer..

  • @khushi-gn1zz
    @khushi-gn1zz 4 года назад

    still didnt get it

  • @2007excalibur2007
    @2007excalibur2007 13 лет назад

    @jonrty007 If he needed to round it off he could've at least just used 10^5 Pa, lawl.

  • @fleshcookie
    @fleshcookie 12 лет назад

    lets say we have that bowl Sal!

  • @littlelulu123456
    @littlelulu123456 10 лет назад +11

    could i just borrow your brain for the mcat nov 7? LOL

  • @bubshab
    @bubshab 13 лет назад

    Think you got your atm to pascal conversion wrong buddy. Cheers for the vid anyways.

  • @chrisbotos
    @chrisbotos 4 года назад

    I don't think you need to know how atm relate to Pa you can just google it and I don't think any exam will require for you to know it

  • @lucasmontec
    @lucasmontec 14 лет назад

    It's still mercury:?

  • @nikunjtiwari2739
    @nikunjtiwari2739 2 года назад

    google says 1atm = 101325 pascals

  • @michaelproctor2529
    @michaelproctor2529 9 лет назад +2

    For those who care, this is why your Beerita doesn't spill all over the restaurant table.

  • @mariyamlee1125
    @mariyamlee1125 5 лет назад

    test tube looked more like a villi!lol!

  • @AzizSobirov
    @AzizSobirov 11 лет назад

    2:45 Vacuum it has 2 u so it must be W lol

  • @KP-wc6hm
    @KP-wc6hm 6 лет назад

    1atm=101325pa

  • @izzyAKAisra
    @izzyAKAisra 13 лет назад +1

    in my physics class my professor drew the same thing and everyone thought he was drawing a DiICK! Guess what the professor said! : " I dont know where you get that from but that's not physics(Russian accent )

  • @abhishek56555
    @abhishek56555 11 лет назад

    noo

  • @MattOGormanSmith
    @MattOGormanSmith 11 лет назад

    In our school, we'd lose a mark for not drawing the negative meniscus on the mercury.

  • @nehaabbasi3741
    @nehaabbasi3741 2 года назад

    Be my physics teacher pls😏

  • @C0rtny
    @C0rtny 12 лет назад

    Did anyone else jump at 2:50 ?

  • @AmirMullick
    @AmirMullick 11 лет назад

    No guitarded0081.

  • @MusicMenacer
    @MusicMenacer 11 лет назад

    the drawings are helpful, but a bit of a waste of time to watch you draw. the mercury for example

  • @coltwhat
    @coltwhat 15 лет назад

    i thought 1 atm = 101300 Pa? =S

  • @Physicsiseverything
    @Physicsiseverything 11 лет назад

    Isnt mercury red??.....

  • @GoodbyeRubyTu3sday
    @GoodbyeRubyTu3sday 8 лет назад

    there is no sea in Paris

  • @noname2useable
    @noname2useable 11 лет назад

    he is american, thats the american pronunciation

  • @TeKNiQ50
    @TeKNiQ50 12 лет назад

    i effing WUB u

  • @travel_n_fun
    @travel_n_fun 14 лет назад

    Ehm, in the formula (bottom right hand corner, you wrote 103,000N/m^3, when it should be m^2 :)...
    Thanks a lot Sal!!!!