8.01x - Lect 28 - Hydrostatics, Archimedes' Principle, Bernoulli's Equation

Hydrostatics - Archimedes' Principle - Fluid Dynamics - What Makes Your Boat Float? - Bernoulli's Equation - Nice Demos
Assignments Lecture 25, 26, 27 and 28: freepdfhosting.com/03ca75eadf.pdf
Solutions Lecture 25, 26, 27 and 28: freepdfhosting.com/f15cd35103.pdf

[@ShadowZZZ]

Watching this great lectures series during corona quarantine to enchance my intellect and educate myself in the meantime more.

[@harshal1uplavikar]

me tooo

[@harshal1uplavikar]

from India ..

[@yevonnaelandrew9553]

That's a very wise decision. Good luck!

[@surendramehriya2011]

Me too also

[@BobbyxZx]

nile red is way better

[@muhammadismail2300]

Why am I watching this? Actually I'm a lecturer in medical school and I had a lecture on blood flow in blood vessels which is based on fluid physics and Bernoulli's rule I couldn't think of anything better to prepare for my lecture than watching your lecture on fluid physics it's a good thing that even doctors are watching your lectures Lot of respect professor From Iraq

[@deveshtayal1515]

Your service and dedication to teach every hungry mind is truly selfless.

[@aceofthebrothelstreet6720]

Resonance??

[@abinavraja8924]

Ok go

[@rabipadhi46]

Just because of you.... Today I can feel hydrostatics practically.... Great thanks to W. Lewin sir... Love from India 💕💖

[@rabipadhi46]

Not only hydrostatics.... Well it's physics which I seem to feel like.... Hope I could ever meet you.... Wanna study in MIT but you don't teach nowadays... Still your lectures are powerful..

[@lecturesbywalterlewin.they9259]

Wonderful!

[@ishwardass3421]

@@lecturesbywalterlewin.they9259 🙏🙏🙏

[@marxcarton3858]

@@lecturesbywalterlewin.they9259 sir, is there any video of quantum mechanics you may have done

[@marxcarton3858]

@@lecturesbywalterlewin.they9259 sir, at 20:02 the balloon will rise considering there is an atmosphere, because of helium you mentioned, there is a buoyant force even when there is no gravitational acceleration, because of difference in densities.

[@slaysae]

You are the best teacher ever ! I really love your teaching ! I wanna wish you a long and happy life !! You are someone irreplaceable in my heart ...I wanna meet you so badly and say how much your teachings helped me ! Also I really loved your birthday series 💕 Thank you so much again professor Lewis!

[@hirensharma3979]

Your lectures contain all theory demonstration and application ,looking forward to binge watch all your content

[@sajadsalehi8648]

Wow.i enjoyed every sec of this lecture. You are the best.

[@markfar4837]

THATS HOW PHYSICS IS TAUGHT.....I AM COMPLETELY AMAZED...... EARLIER I FOUND FLUIDS VERY DIFFICULT TO UNDERSTAND BUT NOW I ENJOYED LEARNING IT IN THIS LECTURE......THE PRACTICAL DEMONSTRATION WERE JUST TOO GOOD.....

[@lecturesbywalterlewin.they9259]

Glad to hear that

[@rajeshchandrakuri5659]

This is the best lecture i have found on Archimedes' principle..just wonderful demonstration.

[@Jivolt]

This is all nice and stuff but the mind blowing part is 0:49

[@Dr10Jeeps]

Dr. Lewin's ability to describe and draw complex principles is amazing.

[@lukeanderson6076]

what a MIND BLOWING lecture

[@tanuj2778]

After watching your lectures I sometimes doubt my intelligence it seems like what the hell i have studied from past 2 years😂😂

[@gilles466]

Thank you so much for these meneer Lewin, ze zijn erg behulpzaam aan mijn understanding van physics

[@velayudhand2341]

Thank you so much professor,... Very easy to understand with your demonstration...

[@gianlucacastro5281]

I think that to understand the pool level problem, it helps being exaggerated. Consider a super dense object, 1 ton with the size of a coin. Now imagine we drop it in a boat that could carry it. Intuitively, the water level would rise significantly to counter the added weight. Now if we drop it in the water, there will be a massive weight relief in the boat and the buoyant force required to keep it floating will be therefore much less. The object has the size of a coin, so the volume of water displaced by it as it sinks is negligible and so is it's buoyancy. The total buoyant force that the water produces will be way less, and so the pool level will drop. As long as the boulder's density is greater than that of water, the same reasoning could be applied.

[@farhaanalam8214]

Binging bigtime on these lectures rn

[@marklee1194]

YES! I studied these exact same concepts, only to better understand them here.

[@poojawolves370]

I wish I could actually sit there and learn these lectures from you

[@voj7138]

How can he make the dotted lines so effortless? Pure skill!

[@musical_lolu4811]

Honestly I haven't the faintest idea.

[@daanhoffman8773]

he uses the other, or wrong point, of the now angled piece of chalk with pressure and speed on the board to make it "skip" like a stone on water

[@AKBARCLASSES]

Thanks again sir... For the first time I have felt Fluids... Before this I had been thinking that in fluid part there is nothing but puzzles... Now I feel very comfortable in fluids.... Can't pay you against this but infinite respect will always be for you...

[@salvaionicle]

"they will get some of their 25000 dollars intuition back"

[@nicklol7878]

44:55 "That's the reason she couldn't get it up. That's what Bernoulli does to you" - Lewis

[@rekhagupta180]

Can't describe the experience, amazing Thank You🙏🙏

[@physicsconceptsbytusharkha7638]

Amazing lecture. And the rod he used in the water to explain stable and unstable equilibrium has colours of Indian flag. :)

[@ptyptypty3]

another CLASSIC Lecture by Dr Walter Lewin :D .. great Demonstrations, Excellent Chalk Board Graphics.... Thank you.

[@lecturesbywalterlewin.they9259]

:)

[@emilia6067]

Best physics teacher as well as the best physics KZbin I've ever come across. No one else comes even close

[@lecturesbywalterlewin.they9259]

:)

[@thegreatest1948]

This lecture is awesome. Thank you ❤️

[@lecturesbywalterlewin.they9259]

:)

[@pierpaolocasamassima8652]

47:28 We can all admire the greatness of the MIT chalks in this shot... no wonder why they sound so satisfying

[@willalston9627]

Um, King Hieron II was called a "virtuous man" by Machiavelli and he had a long and seemingly friendly relationship with Archimedes, and his father (a court astronomer) so he'd hardly "kill" him if he got it wrong. :P Great lecture.

[@mrpotatohed4]

I remember this Archimedes problem from your video - Problem #29 (=

[@BroadeningHorizonsos]

do you have any video on surface tension , capillarity and all that stuff

[@lecturesbywalterlewin.they9259]

I may have covered some of it in 8.01. I do not remember.

[@cayezara8110]

Wow! This is very interesting lecture.

[@sharudeva]

{39:00 -->} You said that when a hole is made in the vessel, water will flow with the same velocity as in the 'syphon case'. But what if both were done simultaneously ? The approximation that v2~0 would not hold good right ?

[@lecturesbywalterlewin.they9259]

both can be used simultaneously. Each would work as if the other was not there.

[@erenpol4t]

I guess the reason for the last problem being the following; when he turns the glass upside down a tiny amount of liquid runs through the microscopic gap between the glass and the cardboard with a high speed, causing so much low pressure thus the Mg of the liquid is supported. Please correct if I'm wrong.

[@Ar-vc9yy]

Whenever a body is partially or completely submerged in a fluid,it will experience an up thrust which is equal to weight of the fluid which has been displaced.

[@binosauras4499]

In the answer to your waterline of swimming pool question, I think it will go down. When we seperate the stone from the boat, the waterline goes down more than the volume of the stone since the density of the boat is lower than the stone. So when the stone sinks the net effect is a lower waterline.

[@luissoto4981]

The water level stays the same

[@skakdosmer]

He (Walter Levin) said it would change! Need I say he is right?

[@maazadnan117]

Always learn something new.

[@yaqubansari8594]

I am in love with physics just because of you. I left my job to teach physics..❤️

[@eamon_concannon]

Is there some intuitive reason for why the pressure is lower at a point in a fluid where the velocity is higher? Thanks very much for the videos.

[@MrEloquentsilence]

Thank you, Professor Lewin!

[@hamiltonianpathondodecahed5236]

7:00 "Consider a spherical cow"

[@ashwanisingh6248]

professor i am from i india, i love to watch your lectures , you explain practically everything. i am in class 10 but i understand everything. it creates me a passion to get phd in physics .thank you professor

[@shaorenong9515]

Should the Navier-Stokes equation be covered for this chapter?

[@nsai3757]

no , i think this video is only for +1 or +2 only , but what are you asking is a undergraduate concept :-) !!!

[@kilimli8824]

Thank you so much, you will be remembered sir

[@francescocuccu4218]

I love each one of your lecture, each one. Thank you so much!

[@Akash_Hegde]

That was one brilliant lecture!

[@mrdark250]

In which lecture surface tension and viscosity are included?

[@alexandartheserb7861]

EUREKA is from REKA, rekao (sam) which on Serbian means Told (I told). Reka also menas river, flows of something, in this case words. It is similar as rhetoRICS, where Rika means roar (also talking meaning, but more in animal terms).

[@harshasn406]

At 38:55, syphen experiment. when we suck the water at other end, we created a differential pressure at top and because of this water is raised to max height of tube. once it crosses the max height, gravitational P.E is converted to K.E which resulted into water fall.

[@abinavraja8924]

Woww

[@jiteshbohra6164]

43:00 what a prank!!

[@anvarva9377]

Dear Prof. Walter Lewin, The Ping ball- Funnel experiment was awesome. In case of inverted position (blowing down), what happens when the velocity is kept on increasing ? Will the ball fall down, stick to the top or stabilizes at level below the initial level ?

[@lecturesbywalterlewin.they9259]

It will probably depend on the kind of funnel that is used but given enough air pressure (from above) it will probably fall out.

[@anvarva9377]

Thank you.

[@ricardosanchezramos5264]

In your questions about the boat and the rock, does the water drop to level ?! I concluded that, is it correct?

[@tareqaziz5636]

@22.22 what happens when i suck out all the air inside (vacuumed) that room? because the balloon has some pressure inside, will it explode? just curious. Btw I always enjoy your lectures.

[@abhayshankar8762]

Most definitely, for any real balloon.

[@kriti522]

At, 35:08 P1

[@sangeetanayak9589]

Just one word. Wow sir. What an amazing lecture. Wish I could meet you someday soon but it happens as if time doesn't allow,, but I'll change it. 😀. For the love of physics -Ayushman(India🇮🇳)

[@vishalmahashabde9632]

Sir, in case of siphon (37.18) will there be limiting value of 'd' so that water will come out through other hole...???

[@carultch]

Yes. The water cannot go higher than about 10 meters from its starting point without vaporizing. But you probably won't try that one.

[@bidhankhirali]

Sir..its wonderful mind blowing and mesmerising and many more...

[@mwalimumushi680]

Good work

[@timetochangetot4094]

Love it.Thanks my professor.

[@anshulthakur8643]

wonderful sir

[@women_in_blue]

sir in your earlier fluid mechanics video in which 5 meter hose magic was shown could we have even generated 0 atm with continuous block and inblow method

[@Raphael_NYC]

Thank you Dr. Lewin. raphael santore

[@frenchy16785]

Love the way he says Boyant (Buoyant)

[@andyde1809]

Regarding the Problem of the cranberry Juice!! If cardboard/paper Surface is 20cm^2 than from atmospheric pressure (100000 Pa) we get 20Kg (200N) pushing on the paper. Instead, inside the galss, the weight of the water can be for example 0.5Kg. So we have 20Kg pushing against 0.5 Kg for example. The air inside the glass is pushing on the water with atmospheric pressure but the total weight (air + juice) that is pushing down on the paper is the weight of the water: so much smaller that force produced by air pressure! Professor Lewin is this correct?

[@SkunZielonyJakMech]

Dear Professor Lewin! I have a question about the syphon. Why fluid does not simply rip into two (at the top of the tube) and the one in ascending part of the tube come back to the tank and the other one in descending part go all the way down? Is it due to attracting forces between fluid molecules, which produce surface tension?

[@lecturesbywalterlewin.they9259]

use google

[@dr.sciencesc.d3088]

Hello Dr. Lewin, this is what I think about the question about the water level changing when you throw the rock overboard. I am a little confused on what you mean by will the water line remain change. Relative to the boat or relative to the walls of the pool? Initially, the water is at a height y_0. The volume of the fluid V_water is given by x*y_0*z where x is width and z is the thickness. For the boat to float, the F_b must equal the weight of the boat and rock. So F_B_0 = (M+m)g (1) where m is the mass of the rock and M is the mass of the boat. Now analyzing the situation when you throw the rock overboard. The mass of the entire boat-rock system must change because we no longer have m. So, in order to float, F_B =Mg. (2) So applying Archimedes Principle to (1.1) V_fluid_0*p_water = V_(M+m)*p_(M+m) and to (2.2) V_fluid*p_water = V_M*p_M . F_B_0 > F_B because of (1) and (2). Therefore. V_fluid_0*p_water > V_fluid*p_water. p_water = M_water/V_water = M_water/x*y_0*z so we have it that: V_fluid_0*M_water_0/xy_oz > V_fluid*M_water/xyz We know that the density of water must remain constant so as we throw the rock overboard, the mass of the fluid M_water increases. So if M_water > M_water_0 and the densities are equivalent, y_0 > y to keep a constant density so the water level will sink.

[@lecturesbywalterlewin.they9259]

+Dr. Science Sc.D please summarize your conclusion yes the water level will go down. You did way more work than was needed. Try this. If the volume of the rock is V when the rock is in the boat, more water is displaced than V (Archimedes). When the rock is at the bottom the water displacement is V. Conclusion ==> the water level goes down when you throw the rock over board. .

[@ms-uj3qe]

+Dr. Science Sc.D In these problem the water level is taken relative to the walls of the pool. If it was to be taken in relation to the boat (and then the question would be if the boat sinks in a little bit or a little less, respectively the water level in relation to the boat would rise or would lower). Coincidently, I think the answer of both of the problems is that the water goes down.

[@jiteshraj9115]

Here; the water level goes down because when the rock was in the the boat the displaced water, is greater then when t it through down.

[@neillin8212]

what if the rock is floating on the water?

[@timetraveler5128]

@@neillin8212 then it stays the same

[@paramitam4002]

Amazing..

[@SrujanGovindu]

AMAZING!!!!

[@vaishalibanerjee7343]

At 10 33, if the density (solid)>density(liquid), wouldn't then h>l ?? Which is clearly not possible.

[@zeustheboerboel3794]

How did the cranberry juice not fall when it was tilted over in 48:00 min?

[@irule11846]

Abjo Das I’m unsure if this is correct but here’s my reasoning. When he inverts the cup, the empty portion above the juice is essentially a weak vacuum with very low pressure. By contrast, the piece of cardboard still feels the full atmospheric pressure pressing it against the cup. Interestingly, however, even though I haven’t done the maths for this claim - I don’t think this will work if the volume or density of liquid is too high. Essentially, you need a fine balance where Patmosphere > (Pcup + weight/area). Is this correct Dr. Lewin?

[@bilalhussein9730]

When the cup is turned upside down, the water wants to fall out. The air-filled cavity is therefore stretched a bit as the gravity pulls down the water. This reduces the air pressure inside the cup, since increasing volume reduces pressure. Eventually this lower pressure pulls upwards with the same force as the weight of the water pulls downwards. The water is now kept in place and the pressure inside is lower than atmospheric pressure outside.

[@axonnet6721]

We usually did it with the glass which was full [of water]. Surprising that it works also with a glass which is 25% empty.

[@aswin_gri]

In this case, the helium balloon is already in motion due to its upward buoyancy force, which is caused by the difference in density between the helium inside the balloon and the air outside. When the container is accelerated forward, the balloon, being part of the container, also experiences the same forward acceleration. Since the air in the container is also accelerated forward, there is no relative motion between the air and the helium balloon. Therefore, the buoyancy force acting on the balloon is not affected, and it will continue to move forward with the container. I think this make the concept INTUITIVE

[@unmamutazul]

Good night Professor. Checking the deduction of Bernoulli's eq. at Resnick....it says that work at A2,P2,v2 (considering your drawing at 29:20) is negative because the force is opposite to the displacement. Why is this so? is it because we are working with a confined fluid? so it applies Pascal's law?

[@lecturesbywalterlewin.they9259]

I derive Bernouilli's eq in one of my 8.01 lectures. Watch it! I cannot add to the clarity of that lecture. You can ask a question about my lecture, please leave Resnick out.

[@unmamutazul]

xD ok. I'll leave Resnick out! Thank you professor.

[@hansonyuen2044]

: . the water level is proportional to the weight of displaced objects = buoyant force ?

[@augijyotbali2131]

This is gold.

[@69532]

Dear professor for me it was astonished, it's plead to u please let me know as we r always taking direction of acceleration due to gravity upwards or downwards only irrespective of what is the direction of external acceleration whether horizontal, vertical but g l never studied about horizontal direction of acceleration due to gravity as u mentioned in case of Apple and balloon. Please reply

[@rajeevnaik3877]

Isn't coanda effect better explanation for the stability of the ping pong ball than bernoulli principle???

[@kamalakannan.1971]

45:04 I lost my mind when the ping pong ball wasn't falling

[@nuclear5641]

I have an answer to the swimming pool question posed at 11:20, but I also have two additional questions regarding the same. The answer to your question: The water level goes down, because if we assume that the density of the stone is greater than the density of water (a reasonable and intuitive assumption), then the stone will sink to the bottom of the pool and settle down. When that happens, the buoyant force that was originally holding up the stone before it was thrown into the water will now be shared between the upward normal force at the bottom of the pool AND the new buoyant force together. Therefore, the new buoyant force is only a fraction of the original buoyant force. Since lower buoyant force displaces lesser water than higher buoyant force, the water level in the pool goes down. (In the event that this is a bottomless pool, then the stone will keep accelerating downwards under its own weight as there is a net force pulling the stone downwards. This net force can only exist if the new buoyant force is lower than its weight, and hence the new buoyant force is lower than the original buoyant force. Thus, the pool level drops). However, I have two variations on the stone that was thrown out: Q 1. What if, instead of a stone, a fish of the same volume as the stone but of the same density as water is thrown out of the boat and into the pool such that the fish goes below the surface of the water but doesn't sink? Would the water level in the pool go up, stay the same, or drop? My (probably wrong) answer: The water level would stay the same. Since the buoyant force is neither being shared by any normal force at the bottom of the tank (as the fish isn't sinking to the pool floor) and nor is the fish accelerating downwards, there is no change in the total buoyant force, which means there is no change in the displaced water. Hence, the water level stays the same. In fact, when the fish is thrown out of the boat, for the brief moment that it is in the air, the water level drops (as the buoyant force drops), but once the fish is under the surface of the water, the water rises again by the same amount that it had dropped, thus equalizing the level. Q 2. What if, instead of a fish, a wooden block of the same volume as the fish but of lower density than water is thrown into the pool such that it floats? Would the water level in the pool go up, stay the same, or drop? My (definitely) wrong answer: The water level would stay the same. There is no change in the total buoyant force here either, as the wooden block isn't sinking to the floor. But I still feel that my answer to this last question is wrong because my inductive reasoning would have led me to believe that if a higher-density object (stone) lowers the water level in the pool, and an equal-density object (fish) keeps the water level the same, then a lower-density object (wood) would have raised the water level. But that is not what the equilibrium equations tell me. Please correct me if I am wrong in any of the above. And yes, your lectures DO make me ♥ physics :)

[@lecturesbywalterlewin.they9259]

Watch my lectures - Your answers are there!

[@haidangstudy]

at 12:23, I know the high immersed of the boat after throwing the rock is definitely less than it before. So the waterline will go down comparing to the origin. Is it true?

[@lecturesbywalterlewin.they9259]

ok

[@12122012cristian]

I consider useful to present the "firefighters paradox": stop the fire or demolish the house? Because the force of the water jet displaces the bricks and other elements of the house structure. the brick floating (short time) on water flux. and as numerical calculation how much water I need in order to dislodge a brick (which force must have water to dissolve a brick) ?

[@lecturesbywalterlewin.they9259]

:)

[@joskokvesic7138]

5:26 how did he know about gravitational acceleration?

[@johnbingham6355]

If the boat has a flat bottom,or otherwise, and is raised to the level of the water,its weight will remain the same,so, if now the stone is thrown into the water will flow overboard so the level of the water will go down,just as the water in Archimedes bath the water fell to the floor.

[@PiotrSuder]

Sir, if something wants to float then it have to be less dense than the fluid that it floats in. So then how ships float if they are made out of metal which is denser than water?

[@kilimli8824]

Their volume is big enough for make them float

[@2lala885]

Hi Professor, I thought only if the glass is fully filled with juice can the cardboard stick to the glass, as 20cm of water can only produce a tiny fraction of 1atm. But I'm not sure what happens when the glass is half filled. Is it because juice and air inside gain GPE relative to the cardboard so the pressure decreases? Could you please give a hint?

[@lecturesbywalterlewin.they9259]

No it does not have to be fully filled.

[@haupham5086]

Because of atmosphere pressure, the juice will not fall out when the glass turned over. I knew and tried this when I was 8 years old.

[@ninevioletcandles]

Can I check if this is correct for swimming pool question thats why less water is displaced when the rock is in the pool? Volume(rock) x Density(rock) x G > Volume(water displaced) x Density(water) x G

[@lecturesbywalterlewin.they9259]

use google

[@dibyanisahu1121]

Can anyone explain me the last part why it happened so water didn't come out?

[@ChrisPBacon-jl7oc]

the temp. inside a balloon and in the surrounding air play a role on the buoyant force no? Is it caused by the expansion of gas increasing the volume thereby increasing the volume of displaced air or is it the temperature effecting the densities of the outside air and the inside air increasing the differential?

[@lecturesbywalterlewin.they9259]

Archimedes' Principle

[@hansenwang4029]

Does it go down because the stone is more dense than water so while it is in the boat is displaces a volume of water equal to its weight but when it is thrown into the water it simply displaces its own volume.

[@lecturesbywalterlewin.they9259]

yes

[@anvarva9377]

Dear Prof. Walter Lewin, How do you explain a boat sinking when a hole is put in it ? Is this because the effective density of boat goes up ? or The amount of displaced fluid goes down ?

[@lecturesbywalterlewin.they9259]

If you put a hole in it above the water line it will not sink. Below the water line then water will flow in the boat with water. If the mean density is larger than 1.0 it will sink. If it is smaller than 1.0 (wooden boat with no cargo and no people) it will not sink.

[@anvarva9377]

Thank you.

[@asishbauri7433]

U r mind blowing professor lewin

[@archi_4851]

Is there any lecture on surface tension?

[@harshameti1066]

Equation of continuity states that A1V1=A2V2 . If A2V1 . How does the velocity increase(how does the fluid gain energy)?

[@faheem4581]

It doesn't gain energy, the velocity of the fluid increases, but the mass traveling through it in a set time will decrease.

[@oximas-oe9vf]

jusct want say you are amazing sir, would love to invite you one day.

[@paulproofmath323]

Please Sir, what will happen to a balloon, if I inflate it on Earth and send it to empty space?

[@saltsalt3385]

sir I think that the water level will go down because the weight of the boat decreases. and the density of the water becomes higher than that of the density of the boat

[@santanuchatterjee654]

Sir, to answer that question at 11:36 , the water level should go down with respect to the boat, which means a smaller portion of the boat will now be submerged underwater because it does not need to displace the amount of fluid equivalent to the stone's weight. Is this correct?

[@lecturesbywalterlewin.they9259]

correct

[@santanuchatterjee654]

@@lecturesbywalterlewin.they9259 Sir , related to this Archimedes Principle , there is a classic problem : What will happen when an ice cube floating in fixed water container melts? All books and every source in internet mentions water level will remain the same. To an approximation it will.But should it not decrease slightly? When the ice is initially floating, the volume of water it displaces will lead to an increase in height of water in the container uniformly , except in the portion where the ice cube is protruding out of the water surface. After all the ice has melted, the volume of water displaced will come back and fill the void created by melted ice thus the height falls, but the new water obtained from melted ice will lead to an increase in water's height uniformly even in the area where the ice cube was protruding initially. As volume of the water is same and exposed area has increased slightly owing to no ice being present now, height should fall slightly though that's infinitesimal. Isn't it?

[@carultch]

@@santanuchatterjee654 If you keep the water at 0 Celsius the whole experiment, and neglect evaporation and condensation, it will remain unchanged in density, and the water level will remain the same. The ice displaces a volume of water exactly equal to its weight. When the ice melts to 0C liquid water, it backfills that volume, and exactly as much volume as it was displacing when solid.

[@yash29210]

Professor in the syphon demonstration, the reason why the water runs against gravity is probably due to two reasons........ 1) you mentioned that area of the tube is much smaller than area of the vessel so this means adhesive force inside the tube will dominate over the weight of the juice. 2) if suppose after juice starts flowing and at some point the flow breaks then at that point there is vaccum while at the end of the tube dipped in juice pressure is 1atm.....so this will also drive the juice upwards.......

[@lecturesbywalterlewin.they9259]

google syphon - it's all there