science question about water and gravity

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i have a question about water and gravity. i remember as a child we had a large fishtank. when we cleaned the tank we removed all the water in an interesting way. we would put a long plastic pipe into the water so that the end of it was on the bottom of the tank, and then we would suck water through to the other end. if the tank was raised and the end of the pipe that was out of the tank was below the level of the end that was in the tank, the water would flow through, even though it had to travel against gravity upwards through the pipe at first as it made its way out of the tank. then we would just watch as the water flowed out into another container below tank level. i hope my description makes sense. i wonder if there is a special scientific name for this phenomenon where the balance of gravity overcomes initial gravity forces. thanks!
 
uhm, pressure I think, the little molecules wanna be more spread out
someone smarter in the ways of the forces will answer this soon
I hope
 
You probably had to start the water flowing in the tube by either sucking at the end with your mouth or submerging the whole rig. This fills the hose to equal pressure. When you turn it over, gravity helps lower the pressure in the one side, so the water from the other end flows in to equalize pressure. Hope that makes sense. It's called a siphon.
 
ultrauber said:
You probably had to start the water flowing in the tube by either sucking at the end with your mouth or submerging the whole rig. This fills the hose to equal pressure. When you turn it over, gravity helps lower the pressure in the one side, so the water from the other end flows in to equalize pressure. Hope that makes sense. It's called a siphon.
Click to expand...

Yeah, you're describing a vacuum or empty space. The pressure from the atmosphere pushes against the water to fill the vacuum and wala, it goes against gravity!
 
This is how I steal gas....

Juuuust kidding. But it's very interesting.
 
yes! stealing gas! why didn't i think of that? i wasted all that energy describing the fishtank. you've got some imagination there, Sandra.
 
...that's why my truck didn't start yesterday...
 
Sorry Kav. I pay 124 a litre for gas up here. I had to get to work somehow.
 
bickelz said:
Yeah, you're describing a vacuum or empty space. The pressure from the atmosphere pushes against the water to fill the vacuum and wala, it goes against gravity!
Click to expand...


"wala"? Do you mean "voil
 
ultrauber said:
You probably had to start the water flowing in the tube by either sucking at the end with your mouth or submerging the whole rig. This fills the hose to equal pressure. When you turn it over, gravity helps lower the pressure in the one side, so the water from the other end flows in to equalize pressure. Hope that makes sense. It's called a siphon.
Click to expand...

bickelz said:
Yeah, you're describing a vacuum or empty space. The pressure from the atmosphere pushes against the water to fill the vacuum and wala, it goes against gravity!
Click to expand...

AHEM... NOT A VACUUM
but if you want to learn about vacuums, here's an interesting fellow Torricelli
He invented the barometer

Firstly... there is not initial gravitational force. Its just Gravitational force.
Also... its important to note... gravity is considered to be very weak. Electromagnetic force is 1.0e36 (1000000000000000000000000000000000000) times stronger. Its also important to note that force is a vector... not only does it have a magnitude but a direction. Earth gravity direction is toward earth.

Now Force is defined as the change in momentum over change in time
Momentum is Mass*Velocity

that being said let us begin... water is polar... it likes to stick together...
to illustrate take a water gun and shoot some at the celling.... good. see how it sticks? cool.

Now consider this. Water is a fluid. So is Air.
Bernoulli's principle states: as the velocity of a fluid increases, the pressure exerted by that fluid decreases. Now this tube of yours exerts normal force(perpendicular to surfaces) . Pressure is a force per unit area. the thinner your tube, the higher pressure the higher flow velocity.

From that we also get Torricelli's Law, which relates initial velocity, gravity, and height to the flow of a liquid out of an opening

Now think of your tank as a bunch of sheets mass stacked up on each other.
Now gravitational force points towards the "bottom" or your container. The sheets of water are being "pushed down" by the ones at the top. Thus there's more pressure. This is why your tube has to have its opening at the bottom of the container. basically there's a pressure differential occuring at the opening of the tube in the water.... which relates to velocity. and since the pressure of the sidewalls of the tube differs from that of the sidewalls of the container... there's going to be a velocity flow in that tube.

water flows out of the tube.

:m027:
 
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