Buoyancy help?

Question

can any one please describe buoyancy for me in terms of pressure, depth, force and density and so on... thanks!

Answer 1

Definition of bouyancy: it is a force. Bouyant force is equal to the weight of the volume of liquid displaced. Pressure and depth have no association with bouyancy. Density is directly related to bouyancy, as density of a liquid determines the weight of a certain volume of that liquid (density is mass per unit volume). If a liquid was more dense ( say mercury vs. water), it would create a greater bouyancy force for the same volume

Take a submarine that weighs x tons sitting in water. It can displace a certain minimum volume of water which would allow it to sink. It would have ballast tanks which are essentially big volumes. To increase its bouyancy, it would fill those tanks with air (released from compressed air stored inside), increasing its displacement volume. That in turn increases its bouyant force making it rise to the surface of the water.

Answer 2

Buoyance is an upward force that is exerted on any object that is immersed, either partially or fully, into a fluid (a gas or liquid), within a gravitational field.

The force of buoyancy is a function of the volume of the immersed object (or at least the part of the object that's actually immersed); and the density of the fluid. Specifically, the buoyancy force is:

F_b = Vρg

Where "V" is the immersed object's volume; "ρ" is the density of the fluid; and "g" is the value of acceleration due to gravity.

Buoyancy happens because of the differential pressure within the fluid. When a fluid is in a gravity field, the fluid's pressure increases as you go down. As a result, when you immerse an object in the fluid, the upward pressure on the bottom of the object will be slightly greater than the downward pressure acting on the top of the object. The difference in pressure results in a slight net upward push, which is the buoyancy.