posted by Tommy .
Suppose you have a very long straw that can reach from a cup of water on the ground level to the top of a
very tall building. When you use a pump to suck on the straw in order to bring water up,
a. you can bring the water up to any height with no problem.
b. you can bring the water up to only a maximum height in the straw, when the pressure of
the water column is approximately equal to the atmospheric pressure.
c. you can bring the water up to only a certain height in the straw, because after it will flash
freeze in the cup.
d. you cannot bring the water up by more than a few inches.
by sucking you are creating a vacuum in the top of the straw. When the air pressure cannot push the water up that high, it stops rising.
That's what a barometer is: a sealed straw with a vacuum at the top.