Physics Quicksheets - Fluids and Solids

[SI units: kg/m³]

Specific Gravity =   =      [No Units]

ρ_water = 10³ kg/m³

W = ρgV

a scalar quantity defined as force per unit area: 

       [SI Units: Pascal = N/m²]

For static fluids of uniform density in a sealed vessel, pressure:

P = ρgh

in a fluid due to gravity somewhere below the surface is given by the equation

P = P₀ + ρgh

Absolute pressure is zero-referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure.

Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted.

P_g = P_abs - P_environment

V₁A₁ = V₂A₂

P + ρv² + ρgh = constant

difference between object's weight in air and weight in fluid:

F_buoyant = ρ_fluidgV_submerged