Pressure in fluids

Pressure in fluids

• Aims Core• Relate (without calculation) the

pressure beneath a liquid surface to depth and to density, using appropriate examples

Pressure in fluids

• Aims Extension• Recall and use the equation p =

hρg

Pressure

• pressure in fluids acts in all directions, not just the direction of the applied force.

Pressure

The pressure at any point in a liquid is created by the weight of liquid above that point.

What is the pressure at the point B?

Pressure in liquids

• The pressure at the same depth is the same everywhere in any fluid

Pressure (pa or N/m2)

Density (kg/m3)

Depth (m)

Strength of gravity (9.8 N/kg)

Pressure experiment

A fluid is a liquid or a gas. A tin can has three holes in the side, it is filled it with water.

What do you observe?

What does this tell you about the pressure in fluids?

The water is forced out a greater distance as you move down the tin can. This is because the pressure is greatest at the bottom - pressure in fluids increases with depth.

Pressure in liquids

• Pressure is directly proportional to the depth.  

Pressure in liquids

• The more dense the liquid, the greater the pressure at any particular deep.

Pressure in liquids

• Pressure is directly proportional to the density.

Pressure in liquids

• The pressure does not depend upon the

shape of the container.

Questions on Pressure in liquids

The density of water is 1.00 x 103 kg/m3.

1) What is the pressure experienced at a point on the bottom of a swimming pool 9 meters in depth?

2) The interior of a submarine located at a depth of 45 meters is maintained at normal atmospheric conditions. Find the total force exerted on a 20 cm by 20 cm square window. Use the density of sea water given above.

3) How many atmospheres is a depth of 100 meters of ocean water?

Answers on Pressure in liquids

1) 189 kPa

2) 1.8 X 10 4 N

3) 11 atm