# Fluid pressure physics homework

1. Sep 14, 2008

### jason_r

A 0.800 m-diameter vat of liquid is 2.70 m deep. The pressure at the bottom of the vat is 1.20 atm.

What is the mass of the liquid in the vat?

2. Sep 15, 2008

### tiny-tim

Welcome to PF!

Hi jason_r! Welcome to PF!

Show us what you've tried, and where you're stuck, and then we'll know how to help.

Hint: find the density first.

3. Sep 16, 2008

### jason_r

Re: Welcome to PF!

so far i have :

PA=P_oA +mg
(1215600)(pi*(0.4)^2)= (1.013x10^5)(pi(0.4)^2) + 9.8m
m=1.04 x 10^4kg

I need confirmation on the answer and if im doing this right
cause i dont have a key or anything
thanks

4. Sep 17, 2008

### tiny-tim

Yes, that's fine:

(I haven't checked your value for 1 atm … and I'm assuming you meant 10^6, so that it matches the 1215600)

You've used a force equation … force on the bottom minus force on the top = weight … P-A - P+A = mg.

You could also have use the pressure equation (that's the one I'd have used): P- - P+ = rho gh.

But they both give the same result, and they're both fine.