# Atmospheric Pressure

1. Oct 17, 2005

### airforce840

This is a problem i have in my homework and i want to learn how to do these and get them right so please dont just give me an answer lol

The desity of the fluid in a tube is 850 kg/m cubic. THe pressure exerted by the atmospher is 1.013x10^5 Pa. What is the pressure P in the container?

I hate the book we are using because i dont think it gets too detailed on what we should do.. it gives 3 examples and none of them are like it is on the problem set..

its Physics An incremental Development SAXON and its our AP Physics book.

2. Oct 17, 2005

### Tide

HINT: At any level in the fluid, the fluid supports the weight of all the fluid directly above it - plus the weight of the all the atmosphere directly above it.

3. Oct 17, 2005

### airforce840

so how would i set this problem up? and thanks for the hint.. i didnt learn that in class so i added it to my personal notes

the way i think im supposed to set this up is distance .21 m times 1.012x1065 x 850 kg/m cubic .. im thinking the density may be throwing me off though..

4. Oct 17, 2005

### Tide

At depth D, the weight of the fluid above that level is $\rho A D g$ where A is the cross sectional area of the column and $\rho$ is the mass density of the fluid. The force bearing downward by the atmosphere is $P_A \times A$. Those two forces are balanced by the pressure of the fluid at depth D: $P_f \times A$.

You should be able to work it out from there! :)