# Surface Pressure and Buoyancy

1. Nov 13, 2007

### drewsteriam

Ok here goes,
A cubical box 25.00 cm on each side is immersed in a fluid. The pressure at the top surface of the box is 109.4 kPa and the pressure on the bottom surface is 112.0 kPa. What is the density of the fluid.

I know density=mass/volume and I know my teacher gave us another long formula in class that I never understood so that is about all I know about these problems.

My attempt at a solution: I dont even know what the problem is asking so I dont have much of an attempt at it. If anyone could explain the concept to me and/or let me know of some formulas that might help me that would be great. Thanks

2. Nov 14, 2007

### Staff: Mentor

The change in pressure is simply $\rho$gh, where $\rho$ is the fluid density and h is the differential height over which the pressure difference is measured.

http://hyperphysics.phy-astr.gsu.edu/hbase/pflu.html

So knowing the pressure at bottom is 109.4 kPa and at top the pressure is 112.0 kPa, equate the difference to $\rho$gh.