Fluid Pressure

Pressure is the force per unit area

• Fluids are substances than can flow because their particles are able to move around

• As these particles move around, they collide with surfaces and other particles

• Particles are light, but they still have a mass and exert a force on the object they collide with. Pressure is force per unit area, so this means the particles exert a pressure

• The pressure of a fluid means a force is exerted normal, at right angles, to any surface in contact with the fluid

• You can calculate the pressure at the surface of a fluid by using:

  p=F/A

Pressure in a liquid depends on depth and density

• Density is a measure of the compactness of a substance. For a given liquid, the density is uniform and it doesn’t vary with shape or size. The density of a gas can vary though
• The more dense a given liquid is, the more particles it has in a certain space. This means there are more particles that are able to collide so the pressure is higher
• As the depth of the liquid increases, the number of particles above that point increases. The weight of these particles adds to the pressure felt at that point, so liquid pressure increases with depth

You can calculate the pressure at a certain depth due to the column of liquid above using:

p=hpg, pressure=height of column in liquid(m) x density of liquid(kg/m3) x gravitational field strength(N/kg)

You could write the answer in standard form so its easier to read

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