130
marble balls floating on water are nice sculptures. why doesn't the water squirt out like when you pinch a garden hose ?
(lemmy.world)
this post was submitted on 12 Jul 2026
130 points (87.8% liked)
No Stupid Questions
48885 readers
1667 users here now
No such thing. Ask away!
!nostupidquestions is a community dedicated to being helpful and answering each others' questions on various topics.
The rules for posting and commenting, besides the rules defined here for lemmy.world, are as follows:
Rules (interactive)
Rule 1- All posts must be legitimate questions. All post titles must include a question.
All posts must be legitimate questions, and all post titles must include a question. Questions that are joke or trolling questions, memes, song lyrics as title, etc. are not allowed here. See Rule 6 for all exceptions.
Rule 2- Your question subject cannot be illegal or NSFW material.
Your question subject cannot be illegal or NSFW material. You will be warned first, banned second.
Rule 3- Do not seek mental, medical and professional help here.
Do not seek mental, medical and professional help here. Breaking this rule will not get you or your post removed, but it will put you at risk, and possibly in danger.
Rule 4- No self promotion or upvote-farming of any kind.
That's it.
Rule 5- No baiting or sealioning or promoting an agenda.
Questions which, instead of being of an innocuous nature, are specifically intended (based on reports and in the opinion of our crack moderation team) to bait users into ideological wars on charged political topics will be removed and the authors warned - or banned - depending on severity.
Rule 6- Regarding META posts and joke questions.
Provided it is about the community itself, you may post non-question posts using the [META] tag on your post title.
On fridays, you are allowed to post meme and troll questions, on the condition that it's in text format only, and conforms with our other rules. These posts MUST include the [NSQ Friday] tag in their title.
If you post a serious question on friday and are looking only for legitimate answers, then please include the [Serious] tag on your post. Irrelevant replies will then be removed by moderators.
Rule 7- You can't intentionally annoy, mock, or harass other members.
If you intentionally annoy, mock, harass, or discriminate against any individual member, you will be removed.
Likewise, if you are a member, sympathiser or a resemblant of a movement that is known to largely hate, mock, discriminate against, and/or want to take lives of a group of people, and you were provably vocal about your hate, then you will be banned on sight.
Rule 8- All comments should try to stay relevant to their parent content.
Rule 9- Reposts from other platforms are not allowed.
Let everyone have their own content.
Rule 10- Majority of bots aren't allowed to participate here. This includes using AI responses and summaries.
Credits
Our breathtaking icon was bestowed upon us by @Cevilia!
The greatest banner of all time: by @TheOneWithTheHair!
founded 3 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Now do a marble that weighs 500 lbs.
It's gonna spray
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.
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.
Why ask a question if you think you know better
It’s all about the pressure; more weight needs more pressure but they tune the pressure to match the weight of the ball.
Bigger marble, bigger hose. It's the same principle scaled up.
The variables in this equation are:
Along with some friction outliers, these can be adjusted to find an equilibrium.
Lol
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