For example, we have a bottle filled with water to the point when there’s no space left in that bottle, is the water still moving as we shake the bottle?
In: Physics
I don’t know about shaking the bottle, but if you apply heat to one end of it, you may end up with a nice convection current.
Yep. Try this. Fill up half the bottle with oil and other half all the way up to the top with water with all the air out. Now shake. You’ll see that water and oil beads would go all over the place and then will settle down eventually. You can put food color in the oil to make it more fun.
Beware really long post:
It depends on your physics model, are you considering the water as a “fluid system” or “water + bottle”?
Are you considering molecules chains?
Are you considering single atoms?
Are you considering single particles?
Assuming you are referring to the most basic model: “water in a bottle”, well, kind of, since friction between the bottle and water, but since you said “100% full” yes and no: take a balloon, fill it up with water, it explodes after a certain point, so, 100% in “””reality””” is almost unachivevable level of balance…
On a 100% assuming it’s perfectly balanced, still depends on how you made it, glass bottle, plastic bottle, ballon bottle(?)… do you think it moves? It might, do you want it to not move? Then, personally would use an alluminum bottle to fill it to 100 with low pressure…(don’t know if every molecules would move, but some of them certainly yes, since, if you shake it very very very fast, you can make the water boil)
You can test this for yourself. Very carefully fill a bottle with water, and add different colours of food colouring as you go along, being careful not to get them mixed too much. Once you’ve filled it all the way to the very top of the neck, cap it and shake it.
Indeed, you can tell from the dye not mixing much more, that the water is not moving much at all.
I don’t get the controversy. This is pretty straightforward.
When you move the bottle, the contents move too. So whether they are moving isn’t the question.
Instead, you’re probably asking if the water is *tubulent*—with some parts of the water are moving relative to others. Again, yes, but not very much. We can see this with food coloring.
A half filled bottle with a drop of food coloring will shake up and distribute the food coloring. A totally filled bottle with a drop food coloring will take much longer to diffuse when shaken. But we also know hot liquid will diffuse colors faster than cold ones. So we know the molecules are still moving at room temperature.
An ideal fluid that cannot compress filled all the way so that there is no room for molecules of water to move around will not be able to move any molecules at all—but it still has a temperature right? So the molecules clearly actually are able to move around. Meaning we know this idealization can not possibly be real.
Depends on what you consider to be movement.
The molecules that make up the water are constantly moving, that’s pretty much the definition of a fluid.
Even if you don’t shake it, the molecules still move, but if you add force, you’ll change the direction of that internal movement.
But the “shape” of the water ,for lack of a better term, will always fit the bottle. In a perfectly rigid bottle, that shape wouldn’t change.
It’s similar to the fact you’re always moving, even if you stand still, because the earth is always circling the sun.
EDIT: which means the water is moving through space at all times as well, shaken or stirred, doesn’t matter.
Tap a bottle on something hard
The water will will try to move, this create pressure
Change in pressure allows a phase change and the liquid can turn into gas
Now bubbles are created inside the liquid
Then water will rush to fill that void
This will create a shockwave that breaks the bottle.
[https://www.youtube.com/watch?v=t8L-XjpOru](https://www.youtube.com/watch?v=t8L-XjpOruc)[c](https://www.youtube.com/watch?v=t8L-XjpOruc)
[https://en.wikipedia.org/wiki/Cavitation](https://en.wikipedia.org/wiki/Cavitation)
Assuming a really perfect 100% fill with water and no air or empty space, there is pretty much zero movement.
There is something to be said about the water pressure being higher in the parts closer to the ground (because of the weight of the water above)
and also in the parts opposite the direction of any force being applied to the bottle while shaking (because it’s being mushed against that side by the rest of the water)
BUT, water doesn’t condense very much at all with these tiny pressure differences. So it wouldn’t result in any detectable movement.
Here’s a thought experiment we can do to illustrate why the water would move within the bottle.
Imagine you have a pot of water filled halfway up, and you spin the pot around. As the metal pot rotates, you’ll see that the water inside it basically doesn’t move, and the reason for this is intuitive. The circular pot doesn’t really have any way to move the water just by rotating, other than friction, and the water has lot of inertia. The water wants to stay put, it doesn’t care whether the container around it moves.
Now imagine that instead of a circular pot, you have a (for whatever reason) oblong, oval shaped pot. You do the same experiment. Is the water going to move as the container rotates around it? It has to, because effectively the shape of its container is changing and the shape of the water has to change to accommodate that. But it still has inertia and doesn’t want to move, so it wouldn’t just all rotate with the container. It would be a much more chaotic (turbulent) movement.
Now extend this idea to a water bottle. Filled or not, as the position of the container changes, the position of the water has to change with it. If you rotate the water bottle sideways (not along its axis), you have an extension of the oval pot scenario. The water has the container pushing it one way and it’s inertia opposing that motion, so you get all kinds of movement within the water.
Trying for a very ELI5 one:
Water is really good at slipping past each other. Imagine getting a necklace of beads and putting it around a large tin on the floor so that the necklace is stretched out around it, though all the beads are still touching each other. Then pull it around the tin.
It will move, because even though every space each bead in the necklace is moving into would be full of another bead, that bead is *also* moving out the way. This is sort of obvious really, it happens any time we have a flat spinning object, but I wanted to focus on the path specifically.
Now imagine that the water can also be full of a million possible paths for closed loops of water to go through, all slipping past each other and with everything on the loop moving out of each other’s way.
So because the water along any loop can all slip relatively freely, you can still get motion even when the space is completely full up, it just has to be rotational motion around those loops.
That’s before you get into the fact that water can actually change density, so that, for example, it can spread the compression waves that correspond to sound. Holding a bottle still and putting a speaker next to it is also moving the water, if not very much.
Most of the motion you’ll get is from loops of water though.
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