(b) Density and pressure

Units of density depend on units used for mass and volume:

E.g. mass in [g] and volume in [cm³] gives density in [g/cm³], however mass in [kg] and volume in [m³] gives density in [kg/m³].

• The density of an object can be found by measuring the mass and volume and applying the formula above to calculate the density.
• For a regular object use a ruler to measure the lengths needed to determine the volume.
• For an irregular object submerge it in water and measure the displaced volume.
• Measure the mass of either type of object using a measuring balance.

Pressure difference [Pa] = Density [kg/m³] x g [N/kg] x Height [m]

ΔP = ρ g h

• The equation can be used in liquids or gases provided you know their densities.

P₁ – P_atm = ρ g h

P₁ = ρ g h + P_atm