Task of building a water barometer.

[killersanta]

Homework Statement

Your physics teacher has assigned you the task of building a water barometer. You've learned that the pressure of the atmosphere can vary by much as 5 percent from 1 standard atmosphere as the weather changes.

A. What is the minimum height you must build your barometer to?
B. When the weather man said the barometric pressure is as low as 29.55 inches, What is the height of your barometer?

The Attempt at a Solution

I don't know where to start. I thought at first to use P = F/A for a closed surface and set that equal to P = Po + Density*g*depth... But, I don't know F or A?

Then, I thought set Po * 5% = Po + D*g*depth... but that gives me the wrong answer...

 

[berkeman]

Homework Statement

Your physics teacher has assigned you the task of building a water barometer. You've learned that the pressure of the atmosphere can vary by much as 5 percent from 1 standard atmosphere as the weather changes.

A. What is the minimum height you must build your barometer to?
B. When the weather man said the barometric pressure is as low as 29.55 inches, What is the height of your barometer?

The Attempt at a Solution

I don't know where to start. I thought at first to use P = F/A for a closed surface and set that equal to P = Po + Density*g*depth... But, I don't know F or A?

Then, I thought set Po * 5% = Po + D*g*depth... but that gives me the wrong answer...

Wikipedia may be of help...

http://en.wikipedia.org/wiki/Barometer#Water-based_barometers

.