Pascal's Law - F-J's Physics - Video 77

Why does "Water always find its own level?" You need to know something about Pascal's Law.

[@viiirs3431]

awesome.... could not find a video with such a good explanation...cleared my doubts

[@AnthonyFrancisJones]

Thanks Kapin - glad you found it useful - I spent quite some time trying to think up a good way of explaining this rather than saying 'This is what happens,' which is not really an explanation. Glad you felt it helped your understanding. Lovely piece of apparatus too.

[@Rizon1985]

There is just one thing you missed while summing up the "understandings". All connected reservoirs have to be in the same enclosed system. So practically the easiest way is to make all containers open and then they are all in the enclosed system of our air. The easy experiment for that is having a bucket of water, put a glass bottom down in it so it fills with water, turn it bottom up and then lift it above the water line of the bucket. The water level will not level out because the water in the bucket and the water in the glass are not subject to the same enclosed system. One of the practical applications where this can trick someone is when they want to store rain water into connected reservoirs. If the reservoirs are airtight from the world atmosphere, the water will equalise over all the reservoirs but it will overflow very quickly from the gutter with very little water in the reservoirs. If all tops of the reservoirs are open, the water will equalise in both the reservoirs and the draining pipe and eventually start pouring out of the reservoir tops.

[@AnthonyFrancisJones]

Thanks very much for this - you are absolutely right and you have given me an idea for another video! It is interesting that with open systems we assume that the system is 'static' and that the open ends are 'infinitely close together' otherwise it would act as a kind of barometer. And then there is the curvature of The Earth...! Isn't physics wonderful! I am very grateful for you taking the time to comment - others will learn from this too.

[@Rizon1985]

​@@AnthonyFrancisJones Thank you for the kind words. I never learned fluid physics or dynamics from a theory. We were young teenagers in the '90s and water cooling computers became a thing for overclockers. Ripping radiotors out of cars, using aquarium pumps and with a hand drill cutting out a heat exchanger from a block of metal. Nothing like the science and manufacturing that exists in the current mature commercialised world of PC water cooling. It's way better now than what we were messing around with back then. But it gave us a lot of practical knowledge about fluids that we would have never guessed. Like being able to run a waterloop with an open reservoir at the lowest point of your circuit and the fluid just keeps circulating instead of pouring out. And you can stop the circulation and still the water won't pour out if your reservoir is open which is very unintuitive behaviour. Or things like galvanic corrosion (we used copper blocks and aluminium radiators) or cavitation (aquarium pumps weren't up to the task of delivering enough pressure, so we ran them with extra voltage but the propellers weren't designed for that). We only learned the names of the rules later and that there were formulas for it all. Pretty much how people controlled water thousands of years before the laws were written down.

[@AnthonyFrancisJones]

@@Rizon1985 Excellent - yes you did learn by application and problem solving - I was explaining only today that our gutter fed water butt cannot overflow even though it is well below the guttering. My dad used to repair car fuses with sweet wrapper foil due to them always failing due to galvanic corrosion. I must admit I still marvel at the liquid cooled Cray computers from 'back in the day'! Thanks again for your extensive comment and experience it only adds to the quality of this little channel!

[@jn3917]

Thanks for the idea. I am a physics teacher and this helps a lot

[@AnthonyFrancisJones]

Thanks and pleased it is of some help! Keep teaching - we need physics teachers!

[@semperfidelis271]

thankyou for explaining Water always find its own level. i have heard it multiple times on other channels without explanation.

[@AnthonyFrancisJones]

No problem Michael - glad you liked it and found it useful. Remember the Earth is curved which adds a whole new level to 'its own level' - no pun intended!

[@semperfidelis271]

@@AnthonyFrancisJones one of the things I did in the navy was i was one of the lookouts, and without a doubt I observed the curvature of the earth.

[@AnthonyFrancisJones]

@@semperfidelis271 Yes, exactly - I think I mentioned in an earlier comment that long bridge pillars are further apart at the top than the bottom!

[@priyanshuvarshney112]

Thank you so much for this video. Could not find a better explanation. :)

[@AnthonyFrancisJones]

Thanks Milan for taking the time to comment - it is such a hard concept to get across whilst trying to explain it. Glad you enjoyed it!

[@dhirajthakur1159]

thank you sir ,wonderful explanation.

[@AnthonyFrancisJones]

My pleasure and glad it was of interest. Thanks very much for watching.

[@divisionbreak]

Can we use Pascal's Law to conquer that the Earth has to be flat because there is no way sea water i.e.: (Pacific Ocean) wraps around the globe/ball even if we consider that gravity is holding the sea water down. Sea water like any other water does not behave (keep still) in any form of curvature. Water always find it's own level/plane.

[@AnthonyFrancisJones]

Good question - no! The level (surface) will always be at 90 degrees to the vertical gravitational field lines at any given place so from a distance the water will look curved. The best example I ever had of this was on the Humber Bridge where the suspension towers on either side of the rive (it's a long river) are measurably closer together at their bases than at their tops! The are still 'locally' vertical and following a gravitational field line. That is a great question and I hope you feel I have used science to explain a solution to it. I am fully aware that a 'flat earther' has a 'belief' that no amount of argument on my behalf can change though it is great that people think these things as it keeps scientists sharp in their thinking an explanations!

[@divisionbreak]

Thank you Anthony. The Humber Bridge example is interesting: \......................../ I am not a hardcore flat earther. But I have been observing, learning & seeking. I try to stay relevant.

[@AnthonyFrancisJones]

@@divisionbreak Great - glad it helped and your diagram explains it well - good science communication and thanks for asking me such a good question!

[@AnthonyFrancisJones]

@Yuppy Guppy Interesting but conflicting two ideas. Yes the Newton's Law of Gravitation force between molecules that form the air is minute but the effect of The Earth's gravitational field is a different matter. Remember we are at the bottom of a 'sea' of air so the pressure is higher the lower you are. Look at planets and other bodies even in The Solar System whose masses are such that they do not have a strong enough gravitational field to retain and atmosphere. Knowing about 3/2kT helps here to understand temperature effects. As ever, even though your idea is a little confused it results in some very interesting comment. Finally, where the effects of gravity between bodies are negligible, such as on Apollo 13, the oxygen did in fact rush out into the vacuum of space!

[@AnthonyFrancisJones]

@Yuppy Guppy I am filming on the shore today actually and it is the slope of the land/beach that causes the waves to roll back when retreating. Not sure what you are implying about rivers but the source is always at a higher gravitational potential (less negative) than the mouth at the sea so it is a flow down hill. It is amazing how many young children when you show them a map or harbour think that rivers flow out of the sea (tidal effects aside) - until they swim, sail or fall into one!

[@stephendewitt8742]

Where are the truth seekers who would dispute this? Not interested? Great work here! Thank you.

[@AnthonyFrancisJones]

Thanks Stephen. Glad you enjoyed the video. I did spend ages trying to find a simple explanation that would be OK without using maths and that was accessible. Thanks for watching and commenting.

[@Puttenoar]

What? That water follows a curve?

[@AnthonyFrancisJones]

Yes, if you extend it far enough to take into account the curvature of the Earth!

[@arushbansal111]

amazing explanation

[@AnthonyFrancisJones]

Thanks - glad it helped. Not an easy one to find a good explanation for!

[@anjaneyasharma322]

Paradox But stranger is the formula that is the one used for Pascals law of pressures. If you take a U shaped vessel instead of the one you have taken for demonstration the results will be different. You have to check whether it matches the statement of the Pascal la on pressures. The problem is getting a U shaped vessel with two tubes of differing diameters.

[@AnthonyFrancisJones]

Interesting - not quite sure what you mean here but if you mean a U tube like that of a manometer with one side wider than the other it still makes no difference at all. It is only Fluid Density and Gravitational Field Strength that would cause a difference in height if the pressures on both sides were the same! One would have an interesting effect if one of the tubes was very narrow. One would have to consider capillary action too. Another idea for a video! Thanks for watching.

[@jn3917]

Thanks for the video ✌️

[@AnthonyFrancisJones]

Thanks. Glad you liked it and it is a lovely piece of apparatus too! Hope you enjoy some of the other videos as well!

[@rishabhrulzzz]

One question sir, if vessel D is pressed, what will be the effect on other vessels?

[@AnthonyFrancisJones]

If I understand you correctly if you were to put a plunger in one vessel or increase the pressure in it then its level would drop and the others rise. Currently they all have one atmosphere of pressure each above the water level. Hope that answers the question. Thanks for asking!

[@sahebjan1736]

if sea water is still then sea top water is levelled same?

[@AnthonyFrancisJones]

Yes, that's correct - remember that 'level' is at 90 degrees to any gravitational field line so 'zooming out' you will see the 'level' follows the curvature of the Earth. This is true of my apparatus too but the pipes are too close together to see this effect. Remember 'level' is an interesting concept as comparing to distant places on the Earth such as the the North Pole and central Africa - water and spirit levels will show a line that is parallel to the Earth's surface but those two 'levels' will look to be at 90 degrees to each other when viewed from space! Many students fine this concept very difficult to grasp but remember 'directly down' for anyone is the direction that gravity pulls them. Good question and thanks for asking.

[@sahebjan1736]

@@AnthonyFrancisJones above same condition is the elevation will be same after 1000 km ?

[@AnthonyFrancisJones]

If I understand your question correctly - if you go up this far above The Earth's surface then it will still work - as long as you are in a place where The Earth's gravitational field is the force acting upon it without the additional effects of other objects such as The Moon etc.

[@user-kq8zq8hh2f]

Thanks🌹

[@AnthonyFrancisJones]

Glad you liked it - I spent ages trying to find a way to explain this satisfactorily!

[@user-kq8zq8hh2f]

Anthony Francis-Jones I studied this for about 12 years in primary school , middle school and high school and it’s the first time I can understand it practical not theoretical Teaching should be an experiment

[@AnthonyFrancisJones]

@@user-kq8zq8hh2f Great! Glad it helped you. Thanks for the comment.

[@bluediamond9693]

I want same video in hindi please someone send me link

[@AnthonyFrancisJones]

Thanks for the question - I am not sure if I can turn on Hindi subtitles - I can try.

[@AnthonyFrancisJones]

Looks like it won't do it automatically which is a shame.

[@josecanyousee4125]

Gravity is still an unproven theory.

[@AnthonyFrancisJones]

Yes, indeed - that's what makes it a theory - though many people refer to Laws of Gravity to try and indicate that it is not unique to a specific region of space.

[@tonymcflattie2450]

Would it also work with urine, asking for a flat earth friend? Lol… great video

[@AnthonyFrancisJones]

Sure it would but I am not sure I would wish to try! Reminds me of a Feynman story...!

[@tiger05rtc]

Pascals Law requires the liquid to be INCOMPRESSABLE so that's why it is true in Transmissions and mechanical operations. The fluid in there cannot be turned into a GAS and is therefore INCOMPRESSABLE. The WATER on the earth is EXPOSED to SEVERAL different temperatures, in many different places that would render the WATER COMPRESSABLE or into a GAS or SOLID. Therefore yes we live inside a enclosed system but that liquid is not uniform throughout the earth because of the many different climates the WATER is subject to and as such pascals law wouldn't even apply. The earth scientifically FLAT.

[@tiger05rtc]

@Anon Ymous 😂

[@MUSIC4TRUTH....]

Thanks for proving the Earth is not a globe.

[@AnthonyFrancisJones]

Interesting point! Yes, there is The Earth and the facsimile of it (a globe on my desk). I only wish I could make this apparatus many miles long and then you would see the difference in levels - but not heights or altitudes of the liquid. I think I mentioned the fact that very long bridges actually have a greater distance between the tops of the towers and the bases. All 'evidence' of course, nothing is 'proof' - the joys of the scientific method!

[@tonymcflattie2450]

Shovel it, flattie!

[@tiger05rtc]

@@AnthonyFrancisJones so what experiment proves sitting bodies of water are curved over the surface? Why do you let theories and peer pressure dictate your beliefs as a scientist. We both know there are no actual experiment that show ANY curvature over bodies of water and it all real science flies in the face of the globe model.

[@doddermodd]

@@tiger05rtc I've measured the curve.

[@tiger05rtc]

@@doddermodd no experiment can prove a lie

[@SM-wx4de]

Floot roop