Hey Ray: The magic bottle
PITTSBURGH (KDKA) - We have done several experiments with pressure and water, and there is a new one I want to show you.
Before we get to that, let's take a look at something you probably already have seen.
One of the first experiments you probably conducted, not knowing it was an experiment, was putting your finger or thumb on the end of a straw that is in a liquid. When you lift it up, and then release your thumb, the water falls out, because air can rush in the top part of the straw, replacing the water inside that drops out.
For this demonstration, I have a bottle with two holes in it, and two straws in those holes.
There is nothing blocking the straws, but no water comes out of the bottle until I lift the orange straw above the yellow straw.
Once it gets to that point, the bottle begins to empty.
When you push the orange straw below the yellow straw, the flow stops.
Remember, air pressure does not just push downward. Air pressure pushes on things in all directions.
This means that the position of the straws is the key to what is happening. Again, the orange straw, when below the yellow straw causes the flow to stop.
When the orange straw is above the yellow straw, the flow starts.
This would be a good time to remind you that there is nothing special about these straws.
We know the air is pushing equally into the yellow straw and the orange straw.
Now look at the water. The water would want to flow out of the yellow straw if air were allowed into the bottle.
Gravity and air pressure at work!
That is obviously not able to happen when the orange straw is below the yellow one, but it is able to happen when you lift the orange straw above the yellow one.
Looking at this bottle, from the top of the water to the bottom of the bottle is a column of water. There is water above and below the yellow straw. Water also fills the orange straw when you push it into the water.
When you push the orange straw's tip below the yellow straw, something happens.
The column of water becomes greater with the orange straw. This essentially causes a pressure difference resulting in the flow going from the yellow straw to the orange one, even though the yellow straw is horizontal!
Since there is not enough pressure to push the water all the way out. When you lift the orange straw up, the water columns smaller, meaning the air pressure pushes down the orange straw, pushing water out of the yellow straw.
Essentially, I made a silly version of a siphon.
