Gravity & Fluid Pressure

• the weight of a fluid can exert a pressure on anything underneath it

• this downward pressure is due to the fluid’s weight and the force of gravity

Pressure = Weight

Area

Gravity & air Pressure

• the air pressure on top of your head is the weight of the column of air divided by the area of the top of your head

• air pressure decreases with altitude

Gravity & water Pressure

• the water pressure at the bottom of a lake or ocean is equal to the weight of the column of water above divided by the area of that column

• water pressure increases with depth due to the force of gravity

Gravity & Ocean Pressure

• if you were to divide the ocean into layers, the top layer at the surface would have the least pressure while the bottom layer (at the greatest depth) would have the greatest pressure because it has the greatest force pushing down on it from all the layers above it

The water at the bottom of the tower is under the greatest pressure. When plugs are removed, the water streaming from the bottom hole is stronger due the increased pressure on that layer.

direction of fluid Pressure

• the pressure caused by a liquid or gas involves pressure pushing down on you due to gravity, as well as the same pressure pushing up and on all sides

• fluid pressure is the same in all directions

Pressure in a Liquid

Liquid pressure acts equally in all directions.

The Bends

Under high pressures in the ocean, N2 gas is absorbed into the blood stream. When a diver quickly returns to the surface, the N2 may form bubbles in the blood stream and act much like a carbonated beverage – this can be very painful and even fatal.

decompression chamber

• A compartment in which atmospheric pressure can be gradually raised or lowered, used especially in readjusting divers or underwater workers to normal atmospheric pressure or in treating decompression sickness.