Can You Figure Out The Hour Glass Buoyancy Problem? 

He literally used telekinesis as if its on a daily basis for him. Maybe the magnets are just to hide evidence 😂

and kettlebell weights are good for holding flip flops

Merry go rounds?

কিন্তু

He must think they are super cool, too. because he kept pointing it out

Agree

i think i am a grown-up now as i know the reasons for his observations

why couldnt you?

And some that we can. During quarantine, I took my kids to a field with some strong magnets and found a couple of tiny meteorites.

I thing the video is wrong! I think friction is minimal but CENTER OF MASS matters. In sand up falling down center of mass going down. we see glass not moving but center of mass do. If I am wrong do glass with sand on one side and don't allow sand go to second side. if friction matters then sand up then glass will float, if sand down glass will sink

The phrasing in his introductions was classic.

Now if we could just get things explained not 42 times in the same video. There's only about 1 minute of actual content in this... And it's good content... He just says the same thing over and over.

he leaves enough unsaid though.... good for inspiration and ideas.

that wasn't boring

@@MadScientist267 He literally has a 1 Min Versions of his experiments channel

No matter how much you vibrate the tube, the problem is the tube is too narrow for the hourglass to ever flip over.

@@jerkofalltrades but the friction would momentarily go away as the glass bodies separate.

Or tie a payload at bottom with a string and tune the density of fluid one weight of sand to support that load and it shouldn't flip over.

@@jerkofalltrades But it doesn't have to flip over to sink, if it did, then friction wouldn't be what causes it to float.

He forgot to show us one thing, what happens if you start with the hourglass at the bottom of the tube? He could’ve pushed it down as he even says in the video with a glass rod

this is some saw torture machine type shit

the hourglass itself is already a timer

@@s_gaming71 yea ok but it auto press button (without camera robot thingy) you should probably become smarter than me if you want to outsmart me i guess lol

Thanks for the new trigger for my bomb.

Think I'll just use... a timer 😉

Life is Unfair 😅

idk i solve this very fast just by looking on it and i dont consider myself a smart person. omg does that mean that humanity is not very smart?!

I did it in 3 minutes.

@@voidex136 imagine being this insecure

Exactly dude, these competitive and school's theoretical exams have murdered totally applications based subjects like Science and computers.

I agree with everything you said other than the water getting denser. The water pressure increases the deeper you go, however the density remains the same as water is essentially incompressible.

I thought about this too. When the pressure is a little higher it pushes it more upwards.

Thats a pretty cool trick.

The center of buoyancy has nothing to do with the amount of buoyant force. The density of water is the same in the container so buoyant force given by Archimedes (only displaced volume matters). This is the reason why the experiment is perplexing at first glance: Buoyant force is the same whether the hourglass has sand on top or bottom. The only explanation is what he said in the video, friction with the container walls

@@damartimantilla hi. Overall buoyant force for the hourglass is the same as you said but the centre of neutral buoyancy changes slightly as the sand moves from top to bottom. That’s why it wants to flip over.

Nope not that cool...... but still... pretty magical. No one ever stares at the movie projector.... instead they are always looking at the screen. 😊

It is not "so much" force. It is a tiny amount. That is why he makes it JUST BARELY floats. Informative, but deceiving by design. At the beginning it is disingenuous to say that it 'floats'. It is very obvious that is is NOT "floating".

I thought the answer was what you wrote in your theory.

If you put the hourglass with sand at the top and drag the hourglass all the way to the bottom, it would stay wedged there. Your theory doesn't exactly hold up for incompressible fluids like water (it actually does hold up in fluids where density increases as you go lower down) because the buoyant force on a body depends only on the volume of the body and the density of the surrounding fluid. If both sections were empty, then they would have the same buoyancy because even though the lower section is at higher pressure, the pressure difference across it is the same as that across the upper section, being equal to the product of fluid density, gravitational acceleration, and depth difference.

@@PunnamarajVinayakTejas I'm sorry for asking stupid questions and wanting to find out in my own way. Clearly you already have all the answers. 🤔

@@ArjenZwerver bruh. I appreciate you trying to find out. I do have a lot of answers with this phenomenon and I wanted to share and help people learn. I apologise for getting so carried away I didn't notice the condescending tone of my comment.

No, the weight of the sand and the "bouyancy" are totally seperate things. The presence of sand in a particular half has no effect on the force the water exerts on the outside surface of the glass.

Exactly

We probably learn more from these too

@@randaranatunga7259 Sri Lankan bro ?

i click on everything faster than my school classes xD

@@necaton even dude porn?

What is the "other side" you are referring to here?

@@vasuyadav2931 I meant from other end of wire which is at a lower level than the first end of wire which is at a upper level

That's what I thought too

I completely overthought it and guessed it was something to do with atmospheric pressure.

You go my guy. I never even thought about it.

Cuz more air like boat

I guess it correctly before he says that

I watched it somewhere else, with a water tube with an hourglass inside, that when you flip, it stays until the time runs out, then floats/sinks

Precisely. This is like an inverted pendulum, in an unstable equilibrium, so it will always tip over.

if you had to write an exam about the topics he showed in his videos you would fail horribly

before I answer the question let me write about my sponsor

Refreshing to get educated without being indoctrinated into the Liberal agenda.

@@Banditt42 oh no not the rainbow in my physics class oh god

That could be a "you" problem tho

Exactly the same line of thought I was following. It certainly results in a weight difference. Though it‘s probably an extremely tiny difference. I guess he would not have arrived at balancing to this accuracy with the wire he wrapped around the middle of the hour glass.

#metoo I also had this thought first the problem is the free fall accelerated sand then hits the bottom and pushes the hourglass downwards again giving its kinetic energy back to the hourglass. :D

I thought so too, but I realised that the total momentum of the system isn't really increasing, since the sand being brought to an abrupt halt at the bottom just gives back that force. So maybe while the flow is still increasing this could hold up?

Or due to change in metacentric hight initially as sand falls down it becomes unstable and sinks down

It was always touching the walls, it's just he changed the angle at the beginning as to not be so obvious.

I want to see this done with a string attached to the end so it can't flip, only sink when the sand moves down.

Yep, this is a fail video for sure.

What ? Tss the friction on the wall ? Anticlimatic..

You are wrong He was not giving the side view at that point

Yup. He pretty clearly explained the second part of your comment in the video…

What i think is if hydrophobic liquid is introduced on the outer surface then the tube might go into an equilibrium wrt the water in the larger tube, but as the water is been pushed alway it stricks with the the inner wall of the larger tube and the force revert backs the smaller tube (mainly it might give us the same result as shown here my hypothesis!!)

Yeah, me too

wow, (not sarcasm).. i'm wondering if you guys are super intelligent. Because.. i used my brain till smoke came out of my ears and i couldn't figure it out.

Wow (sarcasm)

@@trevvrun1 i sounded sarcastic i guess. But, it is pretty hard to figure out the answer, at least for me, till he explained.

YES. That are exactly my thoughts too. It has always the same mass, but the weight depends on how near the grains of sand are to earth ... And it's getting heavier and heavier the deeper it sinks. :-)

I was also thinking along those same lines!!!.. though, I was thinking realitivistically -- it technically does *mass* more when the sand is at the top (yes, weighs less, but masses more) -- the sand at the top has some intrinsic potential kinetic energy and would literally mass more in that configuration according to Einstein... though it would be infinitesimally small. I hadn't thought about your point, though- I wonder if they cancel out?.. probably yours is stronger.

... just thinking about it even more -- as the sand falls, it converts that little bit of extra kinetic energy to heat energy as the sand hits the bottom and jostles around with the sand already at the bottom -- that heat dissipates through the water and escapes from the "closed" system of the hour glass... only reloaded when you exert force again to flip it back over. Gosh physics is cool!!

@@publiconions6313 The warming causes a slight expansion of the glass bulb, making it displace more water. :-)

@@jpolowin0 ooooh.. yah, good point!

Well I don't think he takes that in such a business minded sense. And that's good science should be as non profit as possible

Are his kits still a thing? I was thinking of getting one but I assumed they had ran out

He had Promoted Curiosity Box by Vsause.. He probably doesn't think like that.

It's all science why not? People thiink too much in bussiness terms...

I thought his kits were like " build yourself a vacuum chamber at home" type of thing that you just buy, and these other boxes appear to be more of a subscription service where you receive regular kits to preform specific experiments designed to be accessible to children. There may be a little bit of overlap in the market, but I'd dare say not that much. One you'd buy if you just want your own home made vacuum chamber, the other you would buy if you wanted to get something educational to keep your kids entertained and get them curious about science.

It probably does but the difference would be too small to measure. A small gas bubble forming on the side of the tube would affect the buoyancy more.

well, glass is not elastic,

a pool float doesnt become harder to push down the deeper it is for that reason. buoyancy is always the difference of an objects weight and it's volume times water weight. So there is always the same force pushing it upwards no matter how deep it is. It probably feels that way, because we as humans are weaker in the required positions to push it deeper

@@allylilith5605 That make sense, but it doesn't seem quite right. I did a quick google search, and could not find any info on the topic. I think The Action Lab should try this.

the pool float pushes you up as much as you push it down, so it becomes harder because you aren’t rooted to the ground.

@@allylilith5605 bruh, the deeper you are underwater. the higher the pressure, so the object has to displace more water the deeper you go. It's called the Archimedes principle: The buoyant force exerted on a body immersed in a fluid is equal to the weight of the fluid the body displaces.

Bottom

Good question. I noticed a hinge on the cylinder mounted on the wall. Is a pivot hinge?

This won't confuse anyone with half a brain. It certainly won't confuse your physics teacher. Unless you don't explain that it will only work in a tube or something with a diameter or width smaller than the height of the hour glass.

@@countofst.germain6417 I got confused for a second ..

@@Bui1tDifferentwell I was confused at the start, because what he was saying didn't make any sense, but I didn't realise it was touching the sides. He was just trying to make it sound tricky, but in reality it's very basic.

@@countofst.germain6417 that’s the whole point of it; it’s a trick. Most people aren’t going to notice that the hour glass was touching the sides. The best part of his videos are when he explains the tricks and everything starts to click.

@@countofst.germain6417 classical magician technique employed in the way he framed the introduction. 👍

Great explaination! I would like your thoughts on the weight being the same in both the cases. I was thinking that if the hourglass is inverted and sand is allowed to fall, wouldn't there be the impact force of the particles falling when they hit the bottom surface, adding more forces to the weight. The greater the height, the more this effect would be. What do you think about this?

@@HereToSin My thoughts. When a sand particle drops from the top, there's a moment when the weight of the house glass is reduced by the weight of a sand particle while the sand particle is in free fall. When the sand particle lands, the weight of that sand particle is again added to the weight of the hour glass. additionally, it's possible that with friction and dry sand, electrostatic forces may complicate the process. Finally, while falling, the sand particle accelerates gaining momentum so that on impact, much of that impact goes to shifting other sand particles where much of that energy transferred into making heat, and a tiny a fraction of it gets transferred to the hourglass. So, for a brief moment a collision with a sand particle may make the hour glass appear a little heavier than the hourglass weighs after the hourglass time run out, but it's only going to be a tiny fraction of the weight of a grain of sand, and is probably offset to a large degree by other grains in free fall.

@@kreynolds1123 Thank you for the insight. Have a great day!!

Nah, its the friction,

Huh you are wrong...

@@PPpeepi nothing wrong with having an incorrect hypothesis

@@bugmaster05 where IS the friction?

I think that would have some effect, but at such a small scale it doesn't do much.

Yes you are correct, And the explanation is wrong.

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-JIVrQQ5jRlc.html

Internal forces can never do anything. They always Cancel out

@@LucaPro02 you are the best! Thanks so much!

isn't there a limit to how much friction glass on glass can offer?

@@apbosh1 I don't think so. Friction is always proportional to the force between the two surfaces.

I don't get it.

Remember the time when we walked across the entire universe in just three steps?

All i see is a butt hurt science student that thought he could easily figure out what was going on but still got tricked🤷‍♂️

I thought about water pressure for a few seconds, too. I'm wondering why I and so many missed the friction solution, and I'm thinking it didn't occur to us because in everyday usage, glass on glass is not something we associate with friction, in fact we might even consider it next to frictionless-- but of course, it isn't.

So now you know that buoyancy only depends on pressure difference, not the pressure itself.

@@rodchallis8031 Even if the friction is zero, I still doubt the norm that it goes down.

It also weighs less because it's farther away from the center of the earth...

The Archimede's force acts on flow line, so the lithest part goes up as a scale.

Well it turns, cause its a unstable state to have high mass up if it csn flip. Just draw two states : one where it is completly straight, and one when it is slightly tilted. When you draw the force vectors,you will see, that while it is straight, there wont be any force being able to turn it , cause the gravitationsl force pulls exactly downwards and not perpendicular to the tube. Bit when it gets tilted slighly, you will notice, that there will be a force l, that tries to tilt it more. So its unstable, cause at the point it slightly tilts, it wants to tilt more and more and more, till its flipped with heavy side at the bottom. Then it will be stable. Cause if it slightly tilts, there will be a force against this tilt, and it will tilt back

The falling sand does in fact still have weight in the hour glass frame. One way to account for it is that the sand is pushing air equal to it's weight out of the way but that air is trapped in the hourglass. The sand might not feel it's weight but the hourglass frame does. Measure an hourglass on a scale and note that the weight doesn't change. good thinking though.

@@medleyshift1325 the sand is only pushing air equal to its volume out of the way, not weight. If u consider the limit where the density of the air decreases to 0 as in a vacuum, the sand must be weightless. While the air will be pushed down slightly by the falling sand, it will also be pulled up by the lower air pressure in the top bulb as the sand leaves. While some molecules of air might hit the bottom more frequently during that phase I think that effect is inconsequential. It should still happen though, but I think the net effect is still a decrease in weight. If you consider a bowling ball dropped over a scale in an airtight box where the scale is the entire bottom face, I don't think the scale would register its weight while in free fall.

@@medleyshift1325 That's only true if the sand is at a terminal velocity, which it will not be in that short of a distance.

This is what I was thinking too, but when it started falling after only some sand moved I knew that was wrong. It feels more like a trick since it's just from the hourglass sitting against the side of the container

I feel u are right 👍

Kinda makes sense. It would only lose weight if the momentum is increasing, which is only when the flow rate of the sand is increasing

But since the sand container is not deformable, so there is no way for the water to know where the sand is. The boyant force does not change based on the orientation of the submerged object. Even in a compressable fluid that gets denser with depth. Laying flat the container expereinces 5 newtons of boyant force for each CC of water displaced. Standing on end the higher portion exeperiences lower boyant forces, the the lower end experiences higher boyant forces. resulting in the same average boyant force. My explanation is: the weight does change slightly. When the sand is at the the bottom all the sands weight contributes to the systems weight. But when the sand is at the top and some is falling, the falling sand does not contribute to the weight. If we had a ball in a box, the ball would contribute to the systems weight. If we suddenly turn it over, while the ball was falling in the box, the box system would be lighter since the falling ball is not contributing to the weight. The newly turned over device has a long column of falling sand and therfore 100 grains are in the process of falling and not contributing to the weight. As the sand builds up in the bottom, the length of the column of falling sand decreases (now 50 grains in the state of falling) and thus the weight of the system increase since fewer grains are in the state of falling.

An hourglass alone is enough for me.

@then ur awesome shut

The pressure gradient is what gives rise to bouyancy. If there was no pressure gradient, there would be no bouyancy force. Also it cannot create "more bouyancy", it just creates the bouyancy.

U can't balance it perfectly

Yes or weigh it down with some wire or something.

@@sa-zq4eq well duh its theoretical

@@archity1242 what do u mean

@@sa-zq4eq its obviously not possible to perfectly balance the sand but if you could what would happen

Tell that to my ex🥱

🧐

Yes

There will be a pressure differential, because there will be a column of water in a gravity field. Also, it is not the pressure differential that makes an object float, it is gravity (as in, all objects tend to fall/go down, but the heavier object replaces the lighter one at the bottom, so the lighter is "pushed" upwards).

I understand him but still very true

What

I was thinking the same but probably no. The buoyant force and the mass is constant, so whatever happens inside stays inside. You can get a one-time kick from accelerating some mass downward, but not a constant force. We need more experiments... is hourglass lighter while the sand is falling?

That's not what happening here, watch till the end for the explanation.

@@-TheRealChris True, but I'm just saying that it reminds me of the same experiment. The forces at play are not the same, but it still brings back those memories : in both cases, the fact that the heavier or the lightest part is either on top or at the bottom influences the end result and the buoyancy. Whether it is ultimately due to friction (like here) or another cause (like in the Mythbusters episodes), it still triggers the same 'Hey, I saw something that looks a bit like that, before' reaction. And, yes, putting the heaviest part of the hourglass on the top will increase buoyancy. It won't increase it just by itself : It will increase it indirectly, by causing the situation where friction is forced to intervene. But I can understand how my wording could have sounded a bit ambiguous, in my first post.

Me too

It does make a difference but so marginal it would be indistinguishable. The mass of the falling sand partical is probably not even a tenth of thousandth of the weight of the hour glass. And so the difference in acceleration would be insignificant

Yes. You could maybe remove enough of the friction by greasing the glass surfaces.