Pascal’s Blaising Barrel – Exploding Glass Barrel with Water Pressure

Today we’re going to do an experiment to demonstrate Pascal’s law of hydrostatic pressure. So here we’ve got a 50 litre glass jug of water. I’m going to try to break this using just this amount of water. Who is the little bit skeptical? Oh, there, I know there are some skeptics in the crowd, OK! How many people here believe that this is going, like really believe that this is going to work? We have faith in physics! Let’s see who wins, Katerina or the barrel! But wait… How did such a small amount of water break such a large barrel? Let’s go back to the beginning to understand this. So, what is hydrostatic pressure? You know how when you dive into a swimming pool or in the ocean and you go deep and you feel pressure in your ears pushing your eardrums? As you go deeper you feel more and more pressure in your ear. And that’s pretty intuitive, right? The deeper you go the more pressure. And when I teach pressure in my class my students have no trouble understanding the correlation between depth, or another way to think about it is the height of the water above you when you’re diving. More height more pressure. But what they do have trouble really understanding and grasping and believing is that the height is the only thing that affects the pressure. Think about the hoover dam. They built a huge thick wall there to block the water from falling. That’s not because Lake Mead behind it has so much water in it which is pushing with a huge mass of water. In fact if you took away Lake Mead completely and kept only a thin film of water right where the dam is, going as deep as the damn, you would feel the same pressure as with the whole Lake. And another example is if you had a long thin straw extending a hundred and fifty feet, the pressure at the bottom of the straw would be the same as if you dove in the ocean a hundred and fifty feet deep. I started looking online for videos to try to find other people who have done demonstrations of this, and I actually couldn’t find any. And then I tried to look up how Pascal himself, who’s the guy who thought about this experiment. Blaise Pascal in 1646 he came up with these laws. I tried to find out how he did it. And there was a lot of uncertainty as to how exactly he did it, and even if he did it at all. So here we’ve got a 50 litre glass jug of water, and it’s already full as you can see. And on top of that we have a hose that extends the 155 feet up into the top of Fine Hall. And here we’ve got the water that I’m going to use. One more thing you should know to understand this experiment is that when the pressure of the water goes down it pushes down on top of the liquid right? But that pressure is then evenly distributed throughout the whole volume of the water so the entire jug will feel that same pressure. And in particular every point on the surface of the glass will also feel that pressure. So basically we’re channeling the pressure from this hose throughout the entire glass and if we reach a high enough pressure in theory it should shatter. Even though it’s a simple idea, there were a lot of technical challenges to overcome. For instance, as you pour water down a narrow tube, air bubbles can form the tube, and then the surface tension of the water prevents them from escaping. Adding soap to the water breaks the surface tension, and this allows the air bubbles to travel up the tube more easily. Since this is the first time that we’ve attempted this experiment there were some unforeseen surprises… the water would sometimes get pushed back out of the tube! This was caused by the air bubbles, which at first got compressed by the incoming water, and when they decompressed, like a metal spring, they push the water back up. And things don’t always go as planned. *Oh no!!* Scientific results are almost always presented in their final polished form, and the struggles to achieve them are swept under the rug. It’s important for young students to realize this, so they don’t get discouraged when they inevitably hit a roadblock. Perseverance! Perseverance will win the end! Take two! *Applause*

39 thoughts on “Pascal’s Blaising Barrel – Exploding Glass Barrel with Water Pressure

  1. One question:
    You said that the water presure is distributed evenly.
    But leaving the tube aside and just looking at the liquid of the bottle, should the pressure at a lower point be higher than at a higher point?
    Since that also seems where the bottle burst first:
    At the very bottom:
    Since the bottle's liquid's whole weight is creating the pressure there.

    Or am I wrong there?

  2. Great video, wonderful demo, looking forward to many more! The visual aids and explanations were very well done.

    I realize with the intro you probably want to strike a balance between showing the "hook" (the jug exploding) quickly and also describing the demo setup/physics learning. When what was said was: "I'm going to try to break the jug using just this amount of water" there was no mention of the part the 155 ft tube would play. Something like "… by pouring it into this 155 ft tube" would make the setup at bit more clear and focus the discussion without ruining the surprise. It was not clear to me at the point in the video when the jug shattered what exactly had been done, so it was a bit less impactful. It was clear by the end and maybe it was clear to the people present. Just a little (hopefully constructive) input.

  3. What about a slight alteration to the demonstration? Pre-fill the tube (above the mouth of the jar) and just raise it up to show how it's only the height that matters.

  4. I wonder what the pressure of the water at the bottom end of the tube would be if it were completely filled? I know the bursting pressure of the vessel was ~42PSI at 5:04, but it's too bad you missed the opportunity to connect the gauge directly to the pipe (and just block the other end completely) to get the reading!

  5. Did the barrel break under the weight of the the water in the hose or with the addition of pressure from your syringe.

  6. Why didn't the hydrostatic pressure burst the tube near the bottom. If it was able to break the glass, shouldn't it have been able to burst the plastic tubing?

  7. Классная подтасовка фактов…. для дураков…..
    Девка рукой давит на поршень где-то с силой 6кгс. Площадь поршня шприца где-то 2см². Значит создали давление в 3кгс/см². Это подтверждает и монометр: 42psi = 3Атм. Я думаю любая стеклянная бутылка лопнет от 3 атмосфер. Так вот как "сукин сын" Паскаль бочку поломал !

  8. In order to make this demonstration easier to perform, add the following apparatus.  Just above the safety enclosure, on the thin tube, install a Tee fitting so that the tail of the T is horizontal to the ground.  The other two connections to the fitting remain attached to the bottle hose and the tall building hose in the vertical orientation.  This third horizontal connection would now be open to the atmosphere.  Make sure the bottle and hose are filled with fluid up to the Tee Fitting.  Attach a Valve to open part of the Tee Fitting. The opening of this valve can be incredibly small, even a pin hole sized opening.  You will no longer need soap or glycerin in the fluid.  With the Valve open, pour the fluid from the tower into the long vertical hose from the top floor.  All the air in the vertical column will be expelled via the T fitting and the valve opening.  Once fluid reaches the T fitting and the valve, fluid will begin to escape through the small opening in the valve.  Now close the valve.  <Bam>  Please note: for safety reasons, the valve should either be closed with a stick from a short distance or electrically via a solenoid valve.

  9. By the slow mo it appears the glass barrel broke from the bottom which is probably its strongest point; while the neck of the barre is the weakest. This adds to the idea that there is no shear stress in a fluid at rest and pressure applies the force downward right?

  10. whats the psi that the glass jar withstand?
    My rough calculation is that: I am considering the height of beaker to be 0.5 meter. and assuming a spherical one…
    Without that 150ft tube :Average Pressure on the beaker walls = 2500 pascal or just 0.36 PSI.
    Total force on the walls of beaker is then 2000N. (or 450 pb force)
    With the 150 tube , Pressure exerted to the beaker walls is 2500 + 457,200 : 460,000 pascal or 67 PSI.
    Total force on wall is then 1.45 million N (315K pb force)
    @67PSI, the beaker is definitely going to break…

  11. Were the principle upon which you state the glass container was shattered were true – hydrostatic force/pressure exerted by a liquid is equal to the internal pressure, which as we know is a function only of height – and were your example of swimming underwater water were true – a liquid would have to exert more force than that based upon its weight, and the only means to accomplish that would be expanding, which is impossible [of course you've been schooled that somehow the container imparts the extra pressure – disregarding the fact the container cannot exert a force – it only reacts]. That does not necessarily mean the small amount of water used in the experiment could not shatter a glass container – it depends upon the height of the tube and the thickness of the glass, but the mechanics is not as you (and everyone else that believes tradition rather than physics believes) state, the mechanics is as I explain in my video on hydrostatics).

  12. The best part of this video was keeping in the mistakes, and showing that science isn't always perfect before it goes into the textbooks.

  13. hypothetically lets say there was 500 gallons of water in this tube and barrel combined. That equals to 4,150lb of water. Although I'm confused because this video is showing me that there is a MUCH LARGER pound force due to the height of the column of water above the barrel. Although concidering the water currently weighs 4,150lb, would it take that same amount of force from the bottom to lift the water upwards? or would it take WAY MORE force? please help! thanks

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