Hydrostatic Pressure & Buoyancy force

• In any body of water, the pressure at the surface of the water is equal to atmospheric pressure, but the pressure rises 1 mm Hg for each 13.6 mm distance below the surface; this pressure results from the weight of the water [Hydrostatic pressure]
• The taller the column of fluid, the higher will be the hydrostatic pressure
• Archimedes: “ when an object is immersed in a fluid, the object seems to lose weight, and this loss of weight equals the weight of the fluid displaced by the body”
• This apparent loss of weight is also a force, a buoyant upward force
• An object will float if the weight of the object exactly equals the weight of the fluid displaced because the net force on the object is zero. An object sinks if the weight of the object is greater than the weight of the fluid displaced, and an object will rise if the weight of the object is less than the weight of the fluid displaced [eg air bubbles in blood as bubble of gas weighs less than the amount o blood displaced]

The Buoyant Force [the force diving an object (eg air bubble) upward]:

F = AhD

Force [F] is equal to the area [A] times the height [h] (or depth) times the density of the fluid

Therefore, a greater upward force is exerted the deeper the object is immersed in a fluid

The taller the column of blood is over an air bubble, the greater will be the force making the bubble rise