marble balls floating on water are nice sculptures. why doesn't the water squirt out like when you pinch a garden hose ?

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• phanto@lemmy.ca ⁨13⁩ ⁨hours⁩ ago

  My advice: (not to OP.) Block this guy. I don’t think he understands that he’s not on Reddit and karma doesn’t matter. He’s trolling and wasting your time. He asked, people answered, and now he’s just arguing. Troll behavior. I’m blocking him, and my Lemmy experience will be better for it.

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  • huquad@lemmy.ml ⁨6⁩ ⁨hours⁩ ago

    The way I like to put it. There are no stupid questions, only stupid people

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    • varyingExpertise@feddit.org ⁨3⁩ ⁨hours⁩ ago

      “There are no stupid questions, but there sure are a lot of inquisitive idiots.”

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• MnemonicBump@lemmy.dbzer0.com ⁨15⁩ ⁨hours⁩ ago

  If the water pressure was high enough to spray out, the ball would simply fly off. It’s the perfect equalization of the weight if the ball and the pressure of the water. You can do this yourself at home. Try this:

  Find a marble that fits the opening of your garden hose perfectly. The hold you garden hose upright, place the marble on top (do NOT hold it in place), and begin turning the the valve until you reach the correct pressure. You’ll notice that without enough pressure, nothing happens at all, and with too much pressure, the marble will fly off the top of the house.

  It’s a balancing act

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  • Karmanopoly@lemmy.world ⁨15⁩ ⁨hours⁩ ago

    Now do a marble that weighs 500 lbs.

    It’s gonna spray

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    • jjagaimo@sh.itjust.works ⁨14⁩ ⁨hours⁩ ago

      Why ask a question if you think you know better

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    • Fermion@feddit.nl ⁨14⁩ ⁨hours⁩ ago

      Marble has a density of 0.098 lbs/in^3^. So a 500lb sphere has a volume of 500lb/.098lb/in^3^= 5102 in^3^. That gives a radius of (5102 in^3^ * (3/(4pi)))^(1/3)^= 10.68 in.

      Let’s say the bowl it sits in has 2/3 the radius. So 7.12in. That makes the enclosed surface area pi*( 7.12in) ^2^= 160in^2^. So 500lbs/160in^2^ = 3.14 psi. How fast do you think the water will spray out at 3.14 psi? Without any drag, out of an ideal nozzle, it would be 6.5mph. However, the pressure will actually be higher in the middle and tapers off to 0 at the edge thanks to the flow diverging and drag. So really the pressure drop at the opening is even smaller.

      There’s a lot of lifting area which means you don’t actually need much pressure. You can lift entire buildings with large water bags.

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    • MnemonicBump@lemmy.dbzer0.com ⁨15⁩ ⁨hours⁩ ago

      Bigger marble, bigger hose. It’s the same principle scaled up.

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    • quick_snail@feddit.nl ⁨4⁩ ⁨hours⁩ ago

      This one weighs 9 tons

      en.wikipedia.org/…/File:Reaching_for_the_Stars.jp…

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    • mbp@slrpnk.net ⁨15⁩ ⁨hours⁩ ago

      The variables in this equation are:

      • Diameter of marble
      • weight of marble
      • diameter of "hose"
      • water flow/pressure

      Along with some friction outliers, these can be adjusted to find an equilibrium.

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    • mic_check_one_two@lemmy.dbzer0.com ⁨11⁩ ⁨hours⁩ ago

      Pressure is measured across surface area. The same way buoyancy is measured by water displacement. A larger object has more surface area. 1 PSI of pressure won’t be very much if the object only has 1 square inch of surface. But it would be a lot of pressure if the object has 500 square inches. 30 PSI is enough to keep your car off the ground. A few PSI would be enough to lift a 500lb rock if the surfaces were prepared properly.

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    • chuckleslord@lemmy.world ⁨15⁩ ⁨hours⁩ ago

      For every weight of ball (within a certain density limit. Won’t work with a black hole, for instance) there’s some pressure and volume of water that will balance the weight and size of the ball perfectly to create a thin layer around the entire surface. Once the ball becomes too dense, there’s no volume/ pressure combo that would do the same (the weight would require too much pressure by volume of water, so it would either stop it or fly full force by while barely levitating the ball). But I don’t think whatever density that would be is found in pressures you could find on earth

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    • systemglitch@lemmy.world ⁨13⁩ ⁨hours⁩ ago

      Lol

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    • kaotic@lemmy.world ⁨12⁩ ⁨hours⁩ ago

      It’s all about the pressure; more weight needs more pressure but they tune the pressure to match the weight of the ball.

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• horn_e4_beaver@discuss.tchncs.de ⁨13⁩ ⁨hours⁩ ago

  I know this is No Stupid Questions, bu has something happened to Lemmy?

  Is someone inflitrating lemmy with a load of troll accounts designed to rile up outrage?

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  • SGforce@lemmy.ca ⁨12⁩ ⁨hours⁩ ago

    Totally suspicious behaviour lately

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    • horn_e4_beaver@discuss.tchncs.de ⁨11⁩ ⁨hours⁩ ago

      It could be related to the unseasonally hot weather in Europe/other places?

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  • bluesheep@sh.itjust.works ⁨13⁩ ⁨hours⁩ ago

    I have this guy tagged, he’s been here a while and started by denying the artemis II launch and other stupid shit.

    I kinda get what you mean, there’s this other person using lemmy as his personal IT 101 professor, his posts annoy the shit out of me too. But apart from that it’s them and this guy when I think about idiotic posts

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  • CultLeader4Hire@lemmy.world ⁨13⁩ ⁨hours⁩ ago

    Why would you be outraged by this??

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    • horn_e4_beaver@discuss.tchncs.de ⁨13⁩ ⁨hours⁩ ago

      Go take a look at the responses to comments by op.

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• celeste@kbin.earth ⁨18⁩ ⁨hours⁩ ago

  https://en.wikipedia.org/wiki/Kugel_fountain Is it this kind of thing you're asking about?

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• DarrinBrunner@lemmy.world ⁨18⁩ ⁨hours⁩ ago

  If it were concentrated to one small hole, it would. The same way putting your thumb over the end of a water hose will make the water spray farther. The wide base around the bottom of the sphere gives enough space for the water to come out without squirting far.

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  • turtlesareneat@piefed.ca ⁨18⁩ ⁨hours⁩ ago

    The water being that dirty makes me think they’re flushing it out to finish it, not demonstrating the final product. Maybe there’s some sealant or fine abrasive to help the final fit.

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• Zwuzelmaus@feddit.org ⁨18⁩ ⁨hours⁩ ago

  Why should it squirt out? Who would want that? Think about basics:

  Pressure is force divided by area.

  The weight of the ball (downward force) equals the upward force from the water pressure, then it can float.

  You want the water pressure to be about 1 bar (equal the air), so it does not squirt out.

  From that you get: weight of the ball divided by the partial area of the ball that is in the water equals 1 bar.

  That’s how big and how heavy your ball must be, then it works.

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  • Karmanopoly@lemmy.world ⁨18⁩ ⁨hours⁩ ago

    It’s not floating though

    It’s more like hydroplaning

    At some point the weight of the ball would close off the water and force it out like squirting

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    • MentalEdge@sopuli.xyz ⁨17⁩ ⁨hours⁩ ago

      The water comes out at a single point at high pressure below the sphere.

      It then travels out and exits all around the sphere.

      The water can be pumped below the sphere very slowly, but at high pressure, and that way still lift the sphere.

      The water doesn’t get squeezed and accelerate towards the outside edge, because as it flows outward, the circle gets bigger. The area expands.

      Hence it slows down, drops in pressure, and comes out at a trickle.

      It’s not like pinching a hose. It’s like adding a kink in the hose. There is huge pressure before the kink, amd after the kink the pressure is super low. It makes the water slow down and come out at a trickle. Even though the pressure before the kink is huge.

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    • Zwuzelmaus@feddit.org ⁨18⁩ ⁨hours⁩ ago

      hydroplaning

      Then I don’t know.

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• Casuls_Die_Thrice@lemmy.zip ⁨16⁩ ⁨hours⁩ ago

  GMU’s Manassas campus has something like this; I think it has something to do with the pressure of the water within the basin resulting in an ultra-thin, low-friction “cushion” for the ball to rotate on.

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• haroldfinch@feddit.nl ⁨18⁩ ⁨hours⁩ ago

  To oversimplify the answer, if you put a strong enough ‘garden hose’ beneath the floating sphere, you would still get that ‘spraying effect’ like you do with a garden hose. However, the sphere would no longer ‘float’ in place in thst case.

  Keep in mind that the floating sphere ‘uses the energy of the spray to stay aloft’, balanced against the weight of the sphere. As a result, there is not enough energy left to make the water spray outward like the garden hose does.

  There are many different factors at work to keep the sphere afloat, such as the curved base below it, matching the sphere’s curvature. Again this is an oversimplified explanation, to help explaon the basic concept.

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• Tikiporch@lemmy.world ⁨13⁩ ⁨hours⁩ ago

  Must be magic, like you’re thinking.

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• heartSagan5@lemmy.zip ⁨11⁩ ⁨hours⁩ ago

  Surface tension?

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• perniciousanteater@lemmy.world ⁨16⁩ ⁨hours⁩ ago

  S Q U A R T

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• Nemo@slrpnk.net ⁨18⁩ ⁨hours⁩ ago

  because that force is translated into making the ball spin

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