Upthrust and Fluid Pressure

Fluid Pressure

• Fluids are substances that can flow, because their particles can move around eachother.
• As these particles move around, they collide with surface and other particles.
• Particles are light, but they still have a mass and are able to exert a force on the object they collied with. Pressure is force per unit area, so this means particles exert a pressure.
• The pressure of any fluid means a force is exerted at right angles (normal) to any surface in contact with a fluid.
• Pressure (Pascals) = Force Normal to a Surface Area (N) / Area of that Surface (M^2).
• Density is the measure of how compact a substance is, i.e. how close together the particles in a substance are. 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 given 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.
• Pressure (Pa) = Height of column of liquid (m) x Density of the liquid (kg/m^3) x Gravitational Field Strength (N/kg).

Upthrust

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