# What is the tallest straw that you could, in principle, drink from

ruffkilla
As a stunt, you want to sip some water through a very long, vertical straw. what is the tallest straw that you could, in principle, drink from in this way?

Mentor
Well, what do you think?

ruffkilla
well i know the answer is 10 m if you round gravity to 10 m/s^2. i also know that the pressure on the top of the straw is 0 Pa. but besides that i have no clue, thats why im asking it.

Mentor
When you sip through a straw, what pushes the water up the straw?

ruffkilla
the vacuum created by sucking your cheeks in.
i came up with this solution.
P1 + rough (g) (h1) = P2 + rough (g) (h2)
P1=0, h1=0
so P2 = rough (g)(h2)
1 atm= 1000(10)(h2)
1.01 EE5=1.0EE4(h2)
h2= 10 m

but im not sure.

Mentor
Looks like you've got it. It's atmospheric pressure that pushes the water up the straw. The maximum height of water that can be supported by the air will be found by setting the water pressure ($\rho g h$) equal to atmospheric pressure.