# Longest Straw

1. Dec 5, 2005

### Gott_ist_tot

I recieved a homework problem that I need guidance on where to start.

What is the longest vertical soda straw you could possibly drink from?

I do not know where to start on this problem. A small push in the right direction would be greatly appreciated.

2. Dec 5, 2005

### Gott_ist_tot

As I posted this I had a possible epiphany.

p = $$/rho$$gd

If the depth at which the straw is submerged makes rho*g*d greater than 101.3 kPa than the water above the end of the straw keeps the water down. Although now I know that won't work because that is how deep the straw is not how long it is.

3. Dec 5, 2005

### Staff: Mentor

in TeX, write /rho as \rho to get the correct letter.

Your approach is correct. One must identify the height (depth) of water, which gives a pressure drop of 1 atm, since it is assumed that the reservoir of water is at one atmosphere (101325 Pa) absolute, and the lowest pressure one could achieve is a pure vacuum of ~ 0 Pa.

The only way to obtain a greater head of water is to increase the ambient pressure above 1 atm.