Originally Posted by

**Abelian** Hi,

I am looking to work out the buoyancy pressure of an object of mass 2kg when held in a tank of tap water at a depth of 300mm (final answer in mmHg). Using Archimedes, I have that the buoyancy force is equal to:

P*A*y*g

Where p is the density of the water (I worked this out to be 998.23 kg/m^3 for tap water at 20 degrees, namely room temperature), A is the cross sectional area of the object (the object has dimensions 0.23m x 0.38 m x 0.15 m, the face in the water corresponds to an area of 0.23 x 0.38 = 0.0874m^2), y is the depth at which the object is submerged (0.3 metres) and g is gravity, taken as 9.81.

Then:

998.23*0.0874*0.3*9.81 = 256.76 Newtons.

However, I am then unsure what to do with this. I have buoyancy force, how to I convert to buoyancy pressure?!? Do I use Pressure = Force/Area?!? If I can, which area do I consider, the cross sectional area of the object?!? If I do this, I then have:

Pressure = 2937.757 Pa (Pascals)

so that:

2937.757 Pa = 22.035 Torr.

Then, since 1 mmHg = 1 torr, we have 22.035 mmHg. Is this correct for this problem?!?

Any help would be appreciated.